Analysis of 3D printed Longitudinal Flatfoot Pads with Lattice Structures using Various Microfoaming Filament

Analysis of 3D printed Longitudinal Flatfoot Pads with Lattice Structures using Various Microfoaming Filament | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Analysis of 3D printed Longitudinal Flatfoot Pads with Lattice Structures using Various Microfoaming Filament Dikshita Chowdhury, Imjoo Jung, Sunhee Lee This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8276506/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 12 Jan, 2026 Read the published version in Scientific Reports → Version 1 posted 12 You are reading this latest preprint version Abstract Purpose of this study is to develop longitudinal flatfoot pads using 3D printing technology for support and treatment of the arch. By applying various materials and designs to the pads, the most effective condition was confirmed. The design of the 3D models was inspired by commercially available wool based pads, and fabrication was carried out through fused deposition modeling (FDM) 3D printing. To manufacture products with different hardness levels, five lattice structures (Voronoi, tetrahedral, kagome, rhombic, and icosahedral) as well as a solid structure were applied. For materials, thermoplastic polyurethane (TPU), lightweight thermoplastic polyurethane (LW-TPU) and lightweight polylactic acid (LW-PLA) were used to produce flatfoot pads with various lattice configurations. The manufactured 3D printed longitudinal flatfoot pads were first analyzed in terms of morphology and compressive properties. Subsequently, two selected structures were evaluated under both static standing and walking conditions using plantar pressure analysis to identify the most suitable manufacturing conditions for flatfoot orthotic applications. In conclusion, 3D printed longitudinal flatfoot pads using LW-PLA pads improved contact area and redistributed midfoot pressure, while 3D printed longitudinal flatfoot pads using LW-TPU provided superior outcomes by reducing localized loading and enhancing arch support. Notably, Icosahedral lattices with LW-PLA designs were most effective for arch stabilization. Physical sciences/Engineering Physical sciences/Materials science 3D printed longitudinal flatfoot pads Fused deposition modeling (FDM) 3D printing Lattice structure Foaming materials Compressive property Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction Flatfoot known as pes planus, is a condition in which the medial longitudinal arch collapses, giving the sole a flattened appearance during standing. This deformity alters normal biomechanics, often causing rearfoot eversion, forefoot abduction and excessive inward rolling of the foot 1 , 2 . A common issue is plantar fascia pain, resulting from excessive stress on the thick tissue along the bottom of the foot. The instability of flatfoot can lead to uneven weight distribution, affecting posture and gait, and causing secondary problems such as knee, hip, or lower back pain 3 , 4 . Treatment often involves approaches to reduce pain, improve performance and prevent further issues, with orthotic devices like custom insoles offering arch support and better weight distribution 5 , 6 . To evaluate their effectiveness plantar pressure analysis is widely used by measuring the dynamic and static foot pressures, it serves as a key indicator of foot function and is widely used to assess footwear, orthotics and gait training. Recently, pressure-sensing fiber-based wearable devices have been applied to rehabilitation assistance and plantar pressure monitoring, and research has also been reported that simultaneously implements high sensitivity and a wide detection range 7 , 8 . This analysis reveals how pressure distribution changes after orthotic intervention, offering valuable insights for managing flat feet 9 , 10 . To manage the complications arising from flatfoot, orthotic devices such as custom-made foot pads are used. These are traditionally made from materials such as wool, polyurethane, silicone, or gel 11 , 12 , but with 3D printing, especially fused deposition modeling (FDM), highly personalized designs have become possible 13 – 18 . FDM offers precise control of geometry and distribution, enabling structures with strength, shock absorption, insulation, and vibration damping 19 , 20 , making it widely used for customized orthotic pads in various forms like oval, circular, U-shaped, longitudinal and arch-supporting, to improve comfort, alignment, and performance 21 – 26 . When customizing 3D printed orthotic pads, the choice of material and structure is crucial for ensuring processability, durability, shock absorption and flexibility. Commonly used materials with these factors are polylactic acid (PLA) and thermoplastic polyurethane (TPU), which are suitable for both rigid and flexible applications due to their versatility 27 – 32 . Recently, lightweight PLA (LW-PLA) and lightweight TPU (LW-TPU) have gained attention, due to their microcellular structures that reduce density while maintaining consistency, energy absorption, impact resistance and flexibility, applicable for industrial and biomedical uses 33 , 34 . Beyond materials, structural design is equally important to ensure strength and flexibility in orthotic pads. Lattice structures with lightweight frameworks of interconnected struts, provide high strength with minimal material use and can be modified for strength, flexibility or impact resistance 35 – 39 . Their adaptability makes them valuable in medical implants, footwear and sports, where performance and durability are essential 40 – 45 . Previous research has analyzed the use of lightweight TPU in footwear applications through FDM 3D printing. Customized outsole designs with varying star-shaped (3-, 4- and 6- pointed) patterns and thicknesses (5, 7.5, 10 mm) were tested for density and rigidity, with the LW 3PS-10 prototype demonstrating superior durability and safety while maintaining comfort across other variations 46 . Similarly, comparative studies of wool felt and 3D-printed TPU foot correction pads revealed that although TPU pads were slightly heavier due to higher density, they provided enhanced durability, support, and shock absorption 47 . Together, these findings highlight the potential of a 3D printed customized pads as a long-lasting and high-performance material for foot support and comfort. This research aimed to improve the medial arch support and redistribute plantar pressure in the midfoot of individuals with flatfoot, by developing and evaluating 3D printed longitudinal flatfoot pads using lattice and solid (SL) structures fabricated with lightweight 3D printing filaments. The pads were first analyzed in terms of morphology and compression properties. Based on these results, two lattice structures were selected for further evaluation under both static and walking using plantar pressure analysis, which evaluated foot pressure distribution. The findings from all the three analysis were then compared to identify the most suitable lattice structure and material combination for effective orthotic applications that enhance comfort and promote proper foot alignment in daily footwear. Results and discussion Morphology of 3D printed longitudinal flatfoot pads applied various lattice structure and filament. As observed in Fig. 1 (a) , each lattice structure displayed distinct characteristics. The nozzle movements of the first layer were analyzed for each lattice structure to gain a better understanding of the denseness of the lattices. The ICO-H strut unit, closed on all sides, was compact with minimal gaps, forming tightly packed triangular struts into hexagonal cells. It was among the stiffest lattices, requiring 13,302 − 13,458 nozzle movements. The RHM structure, with intersecting rectangles and open ends, produced dense layers and showed 19,195 − 19,617 nozzle movements, making it one of the densest designs 48 , 49 . KGM, with closed but small struts and open spacing, formed porous hexagonal cells and required only 7,337-7,552 movements. TET-H, similar to RHM but with slight gaps, showed intermediate density with 13,914 − 14,466 movements. VOR, resembling KGM but with the most open spacing and prominent hexagonal gaps, exhibited high porosity and low nozzle movements of 7,371-7,551 50, 51 . The analysis indicated that nozzle path values correlate with the structural characteristics of the lattices. ICO-H and RHM were identified as the stiffest and densest structures with ICO-H having the intricate high-density geometry resulted in consistently high nozzle movements, while RHM exhibited the greatest inconsistency with the highest overall counts. In contrast, TET-H demonstrated an intermediate density, whereas KGM and VOR with their larger gaps between struts, displayed greater porosity and lower nozzle movements. Figure 1 (b) shows the morphology and thickness variations of 3D printed longitudinal flatfoot pads using different filaments. As seen in Fig. 3 b, TPU samples had clear, smooth surfaces without microfoaming, while LW-TPU and LW-PLA exhibited rough, foamed surfaces, consistent with previous findings 52 , 53 . Among LW-PLA samples, ICO-H_LW-PLA showed the highest wall thickness of 2.16 ± 0.05 mm, whereas VOR_LW-PLA had the lowest of 0.93 ± 0.02 mm. In LW-TPU, ICO-H again displayed the highest thickness, with VOR the lowest, ICO-H_LW-TPU reached 2.19 ± 0.03 mm, exceeding ICO-H_LW-PLA due to stronger foaming. For TPU, ICO-H maintained the highest thickness across lattices, while RHM_TPU recorded the lowest of 0.66 ± 0.06 mm. The morphology and wall thickness of the 3D printed longitudinal flatfoot pads depended on both filament type and lattice structures. TPU showed smooth surfaces, while LW-TPU and LW-PLA exhibited microfoaming. ICO-H lattices consistently had the greatest thickness, with ICO-H_LW-TPU being the thickest, and VOR and RHM_TPU the thinnest. These findings demonstrate that filament choice and lattice design critically affect the structural properties of the 3D printed longitudinal flatfoot pads. Ratio analysis of time and weight of 3D printed longitudinal flatfoot pads applied various lattice structure and filament. Figure 2 (a) shows the time ratio of all lattice structures. It was observed that ICO-H showed the highest printing time, while VOR had the least for both left and right lattices. ICO-H_L took 5 h 25 m 26 s, the longest, due to its closely packed and ordered unit cells, while ICO-H_R required 5 h 20 m 21 s. RHM structures also showed longer times because of high density. TET-H and KGM took less time since their unit cells were less dense. VOR structures were the fastest at around 2 h 40 m 49 s, owing to open, less compact unit cells that made printing more efficient 54 – 56 . Figure 2 (b) shows the weight ratio of the 3D printed longitudinal flatfoot pads with various lattice structures at 10% infill density, produced using different filaments. It was seen that ICO-H has the highest weight and VOR has the lowest weight for both left and right lattices. Similar to ICO-H, RHM structures also have the higher weight. While the weights in the TET-H and KGM structures were more similar and while the SL and WL structures also showed nearly similar weights, except for SL_LW-PLA. The VOR structure had the least weight. This lighter weight was due to their less dense and less packed unit cell structures compared to others, where it was seen that VOR_TPU had the lowest weight of 5.96 ± 0.10 g, while ICO-H_LW-PLA had the highest weight of 13.86 ± 0.32 g 57, 58 . Therefore, it was observed that printing time and weight strongly depended on lattice complexity, denser patterns take longer to print and weigh more, while simpler ones print faster and weigh less. Small variations within samples were due to Carbon’s design engine, which generated slightly different left and right lattice geometries despite identical sample sizes. Compressive property of 3D printed longitudinal flatfoot pads applied various lattice structure and filament. Figure 3 illustrates the S-S characteristics and compressive properties of five lattice-structured 3D-printed longitudinal flatfoot pads with different filaments. In Fig. 3 (a-c) , TPU showed high strength with minimal deformation, LW-TPU balanced compressive stress with higher elongation, and LW-PLA displayed the steepest curve with the highest compressive stress at low strain, indicating easy deformation under stress. ICO-H_LW-PLA had the highest compressive initial modulus of 5.23 ± 0.26 MPa, while VOR_TPU had the lowest of 0.06 ± 0.01 MPa among the lattice structures. In comparison, WL_TPU and SL_TPU showed the overall lowest values, with 0.00 ± 0.00 MPa and 0.01 ± 0.00 MPa, respectively, among all the structures. Compressive stress decreased in the order RHM > KGM > TET-H > SL > WL, among filaments, TPU showed the lowest compressive stress and LW-PLA the highest. In Fig. 3 (d-f) , WL and SL showed the lowest compressive values among all materials and structures. TPU exhibited the lowest compressive properties but higher than WL, LW-TPU demonstrated the highest toughness and LW-PLA displayed the highest initial modulus and stress at 15%, indicating high strength but low toughness. ICO-H_LW-TPU recorded a compressive initial modulus of 0.28 ± 0.02 MPa, compressive stress of 0.08 ± 0.11 kN at 15% strain, and the highest toughness of 7.58 ± 0.45 J. VOR_LW-TPU had the lowest compressive initial modulus of 0.09 ± 0.01 MPa and compressive stress of 0.13 ± 0.01 kN, while TET-H showed the lowest toughness of 2.38 ± 0.02 J. Among lattice designs, ICO-H provides the greatest strength and stiffness, while VOR is the most flexible and porous, with RHM, KGM, and TET-H in between 59 – 63 . Therefore, it is observed that LW-TPU structures showed moderate compressive stress and higher toughness indicating good strength, exceptional energy absorption, and strong resistance to deformation. In terms of the lattice structures, ICO-H lattice had the highest initial modulus and high compressive stress exhibiting it as the most superior lattice structure in terms of strength and stiffness. On the other hand, VOR variants showed high flexibility but low strength, and TET-H exhibited the lowest toughness, reflecting minimal resistance to deformation. Observing the results of compressive analysis, SL, VOR and ICO-H structures were used forward to analyze the plantar pressure test. Table 1 Thermal properties of various filament for 3D printing PLA LW-PLA TPU LW-TPU 1st T g (℃) 64.92 63.40 77.29 69.18 T c (℃) 114.86 117.25 - - T m (℃) 148.69 152.16 / 193.34 226.42 159.70 / 194.37 ∆ H (J/g) 23.81 23.43 / 0.39 11.52 3.47 / 0.49 2nd T g (℃) - - - - T c (℃) - - 88.40 53.49 T m (℃) - - - - ∆ H (J/g) - - - - 3rd T g (℃) 47.63 46.39 156.52 129.84 T c (℃) 114.55 - - - T m (℃) 138.00 143.87 189.77 - ∆ H (J/g) 8.68 0.47 2.00 - Static motion plantar pressure analysis of 3D printed longitudinal flatfoot pads applied three types of lattice structure and filament. Plantar pressure analysis was conducted to evaluate the wearability of the 3D printed longitudinal flatfoot pads according to its material and design. Figure 4 indicates zone classification and plantar pressure diagrams in a static motion during wearing 3D printed longitudinal flatfoot pads. Based on the results of the characteristic analysis of 3D printed longitudinal pads, two lattice structures were selected and analyzed. VOR, which had the lowest density among the lattice structures, and ICO-H, which had high density and therefore high strength. As shown as Fig. 4 , in the NF, pressure was primarily concentrated at the heel and forefoot, with relatively low values observed in the MF region, forming a typical two-peak support pattern. Across the shoe conditions, BF and SC exhibited distinct heel and forefoot loading. Including wool (WL) condition, wearing 3D printed pads status showed a broader contact area with partial pressure redistribution. For the 3D printed longitudinal flatfoot pads, TPU, LW-TPU, and LW-PLA demonstrated material-dependent differences. In particular, LW-PLA maintained relatively localized forefoot pressures and reduced pressure for heel. In contrast, the FF revealed a markedly different pressure distribution compared to NF. Due to arch collapse, high pressure was consistently detected in the all regions and had broad contact area in MF region. Thus, it was confirmed that a three-point support pattern was involved the heel, midfoot, and forefoot. BF status showed a distinct concentration of pressure in the midfoot, clearly differentiating flatfoot from the NF. And while WL demonstrated extended pressure coverage, it failed to sufficiently relieve MF loading, resulting in increased pressure in the forefoot area. Among the 3D printed longitudinal flatfoot pads conditions, as the area of the MF appears to be wider, it was confirmed providing arch support. By materials, while TPU and LW-TPU presented high forefoot pressures, LW-PLA revealed that pressure concentration in the forefoot and midfoot was decreased. And in particular, in both the NF and FF groups, the ICO-H structure was observed to reduce the pressure on the forefoot and heel. Accordingly, it was confirmed that 3D printed longitudinal flatfoot pads exhibited differences in plantar pressure depending on the material and design. For FF conditions, rigid orthotics have been reported to increase arch height and enhance ankle stability as contributing to pressure redistribution and improved wearing comfort. In particular, in cases of moderate to severe flatfoot or adult-acquired flatfoot with marked deformity or instability, rigid or semi-rigid orthotics have been shown to be effective in providing corrective support 64 – 66 . Therefore, this study confirmed that the ICO-H longitudinal flatfoot pad made of LW-PLA showed the most effective pressure distribution with relatively mitigated MF pressure and increased contact area during static motion. Walking plantar peak pressure analysis of 3D printed longitudinal flatfoot pads with three types of lattice structure and filament. Figure 5 shows peak pressure at the M1, M3, and MF zones during walking motion. To determine the differences between NF and FF, this study focused on M1, M3, and MF around the arch. In terms of plantar peak pressure during walking motion, the groups of NF and FF showed some difference results. For the NF group, the BF was 10.90 ± 2.24 N/cm 2 for M1, 16.96 ± 2.50 N/cm 2 for M3, and 7.38 ± 2.72 N/cm 2 for MF, respectively. M3 located the center of the forefoot exhibited the highest peak pressure. And when wearing the 3D printed longitudinal pads, peak pressure values were decreased in all zones compared to the BF status. In the M1 zone, peak pressure of ICO-H_LW-PLA was the lowest pressure for 9.24 ± 1.83 N/cm 2 . In terms of M3 and MF zone, SL_LW-LA appeared the lowest value as 14.03 ± 2.97 N/cm 2 and 6.41 ± 1.47 N/cm 2 . For the FF group, a similar tendency was observed with NF group. The BF status for the FF group were 9.48 ± 2.20 N/cm 2 in M1, 14.78 ± 3.18 N/cm 2 for M3, and 8.22 ± 2.18 N/cm 2 for MF, respectively. Compared to the NF group, as the pressures in M1 and M3 decreased, the pressure in the MF zone increased. It indicated that the collapse of the arch led to a greater load and increased pressure load in the MF zone. In the M1 and MF zones, wearing the 3D printed longitudinal pads resulted in a decrease in peak pressure compared to the BF zone. Conversely, in the M3 zone, the values were generally higher. This phenomenon can be attributed to the redistribution of force toward the medial arch, where the pads provided support. Also, similar to the NF group, ICO-H_LW-TPU exhibited the greatest peak pressure reduction in M1 for 8.21 ± 2.38 N/cm 2 , while SL_LW-PLA showed the greatest peak pressure reduction for 13.82 ± 3.27 N/cm 2 and 7.28 ± 1.14 N/cm 2 in M3 and MF. Regarding the compressive properties, SL_LW-PLA was found to be the higher strength than all TPU and LW-TPU pads. However, when compressed above 10%, it showed the lowest strength among LW-PLA pads. Furthermore, in the M1 and M3 zones, LW-PLA pads were found to be able to reduce plantar pressure. Whereas in MF, VOR_LW-PLA and ICO-H_LW-PLA showed increased peak pressures of 7.75 ± 1.15 N/cm 2 and 7.83 ± 1.46 N/cm 2 , respectively. Some studies have reported that while high-rigidity flatfoot orthotics can increase the arch height. However, excessive rigidity can increase plantar peak pressure and foot fatigue 66 – 68 . Accordingly, ICO-H_LW-PLA was found to be excessively rigid to effectively distribute plantar pressure. Walking contact area analysis of 3D printed longitudinal flatfoot pads with three types of lattice structure and filament. Figure 6 indicates walking motion’s contact areas at the M1, M3, and MF zones. For the NF group, contact area of BF was 15.36 ± 1.52% in M1, 9.04 ± 1.20% in M3, and 21.73 ± 4.84% in MF, respectively. Also, when wearing the 3D printed longitudinal pad, the contact area values were found to increase compared to BF. In particular, the contact area in the MF zone of the NF increased from 21.73% to 26.44–36.08%. The highest contact area values were observed when wearing SL_LW-PLA in M1 for 18.48 ± 1.38% and MF for 36.08 ± 4.92%, and ICO-H_LW-TPU in M3 for 9.80 ± 1.07%. In particular, for the 3D printed longitudinal flatfoot pad made of LW-PLA, SL_LW-PLA, VOR_LW-PLA, and ICO-H_LW-PLA exhibited values of 36.08 ± 4.92%, 35.04 ± 4.76%, and 34.37 ± 5.23%, respectively, representing substantial increases of approximately 58–66%. It demonstrated a redistribution of plantar pressure toward the arch. Also, in all zone, significant differences were confirmed as both material and lattice structure can affect contact area during gait. In the FF group, FF had a larger contact area overall, especially in the arch-related M1 and MF zones compared to NF group. Also, as FF had the collapsed arch and broader plantar coverage, no significant effect was observed in the M3 zone though the differences compared to other pads were less resulted than in NF group. In the M1 zone, SL_LW-PLA and VR_LW-PLA exhibited the largest contact area as 20.02 ± 2.09% and 20.05 ± 2.02% compared to BF status as 19.14 ± 2.10%. Especially, in MF zone, BF status already appeared high contact area for 33. 09 ± 2.89%. It increased to over 40% in SL_LW-PLA for 42.05 ± 4.05%, VR_LW-PLA for 40.29 ± 5.32%, and IC_LW-PLA 40.32 ± 5.01%. And statistical analysis confirmed significant differences in the M3 and MF zones, while the difference was not significant in M1 zone as p value for 0.122. Thus, these results indicated that contact area expansion was more pronounced in the MF zone, especially in FF where the collapse of the arch inherently increased plantar pressure in MF. And the 3D printed longitudinal flatfoot pads made of LW-PLA were most effective in enlarging the contact area and pressure distribution. In addition, wearing 3D printed longitudinal flatfoot pads can improve arch support as increasing contact area with balancing the contributions with the moderate increases in M1 and M3. Conclusion This study aimed to identify the most effective materials and design for flatfoot patients by manufacturing a 3D printed longitudinal flatfoot pad. The pads were fabricated using various microfoaming filaments for TPU, LW-TPU, LW-PLA and lattice structures for VOR, TET-H, KGM, RHM, ICO-H. The structural characteristics of modeling, output efficiency, compressive properties, and improvement of plantar pressure distribution were comprehensively analyzed. The results confirmed that the composite materials and structural design significantly impacted arch support and pressure distribution in patients with flatfoot. As results of 3D printed longitudinal flatfoot pads, morphological and compressive properties revealed that ICO-H lattice structured with high density exhibited superior strength, whereas VOR provided higher flexibility with reduced strength. These mechanical properties contributed to plantar pressure responses during both static and walking motions. For plantar pressure analysis, under static motion, pad LW-PLA applied ICO-H effectively reduced MF pressure with enlarging contact area. Thereby it can provide enhanced arch support compared to BF and WL. During walking motion, peak plantar pressures were reduced across the M1, M3, and MF zones when wearing 3D printed longitudinal flatfoot pads. Furthermore, contact area analyses confirmed that LW-PLA pads substantially increased MF zones by up to 66% in NF and exceeding 40% in FF. Thus, it was confirmed that 3D printed longitudinal flatfoot pads with LW-PLA improved pressure redistribution toward the arch. Therefore, this study reported that lattice structured pads fabricated with LW filaments can provide functional improvements over conventional pads. Specifically, the SL and ICO-H designs combined with LW-PLA achieved an optimal balance between stiffness and flexibility, ensuring both effective pressure reduction and increased contact area expansion. These results can suggest that 3D printed lattice based flatfoot pads are a promising solution for flatfoot treatment as offering enhances arch stability, reduces localized load, and enhances comfort during everyday walking activities. In future research, this study will be utilized as fundamental data to conduct customized modeling based on individual patient foot data and to apply different designs by region in order to identify more effective modeling strategies for flatfoot. Methods Materials. To manufacture the 3D printed longitudinal flatfoot pads, three types of filaments of thermoplastic polyurethane (eflex, Esun Co. Ltd., China), lightweight thermoplastic polyurethane (Varioshore TPU, ColorFabb, Netherlands) and lightweight polylactic acid (LW-PLA, ColorFabb, Netherlands) filaments with a diameter of 1.75 mm were used. 3D printing was conducted using an FDM technique with a 3D printer (Cubicon single plus, Cubicon Co. Ltd., Korea) equipped with a 0.4 mm diameter nozzle. Sample preparation of 3D printed longitudinal flatfoot pads. Figure 7 (a) shows the modeling, slicing and 3D printed longitudinal flatfoot pads with a size of 59.03 ×86.64 ×7.06 mm³ using design engine (Carbon, USA). The 3D model of the longitudinal flatfoot pads were saved in *.stl files. The slicing of the 3D printed longitudinal flat foot pads. Slicing was performed using the Cubicreator4 V4.4.0 slicing program (Cubicon Co. Ltd., Korea) under the following conditions, nozzle temperatures of 230 ℃ for TPU and LW_PLA filaments and 240 ℃ for LW-TPU filaments, a bed temperature of 65 ℃ for the LW-PLA filaments and room temperature for TPU and LW-TPU filaments, a printing speed of 60 mm/sec, infill pattern of zigzag and 10% infill density. *.stl files were converted into printable *.g-code files within the slicing program. The longitudinal flatfoot pads were manufactured using a solid (SL) structure and five different lattice structures and their mechanical properties were further compared with those of a wool (WL) pad. Figure 7 (b) shows the detailed lattice structures of five different lattices, i.e., voronoi (VOR), tetrahedral (TET-H), kagome (KGM), rhombic (RHM) and icosahedral (ICO-H) using the design engine. Firstly, in the modeling program, the strut lattices were set and was solidified, and the 3D model of the longitudinal arch pads was saved in *.stl files. The *.stl files were uploaded in the slicing program, the 3D printed conditions were set and *.stl files were converted into printable *.g-code files within the slicing program. As all the samples were of the same size, the samples consisted of a total of 39 layers, including 3 layers of the inner wall and 3 layers of the outer wall, with the rest being infill layers. Characterization. In this study, a 3D printed longitudinal flatfoot pad and its wearability were evaluated. First, the characterization of the 3D printed longitudinal flatfoot pad was conducted as follows. In case of morphology, microscope (NTZ-6000, Nextecvision Co. Ltd., Korea) was used to check the morphology of the various lattice structures of the 3D printed longitudinal flatfoot pads using various filaments. The magnification used was ×4.55 to check the cell wall thickness of the samples. About ratio of time and weight, the time was recorded with the help of the display on the 3D printer (Cubicon Inc., Republic of Korea). The time ratios of the various 3D printed longitudinal flatfoot pads were calculated using the total printing time of the SL lattice structure as the baseline, as it required the least printing time, as shown in equation (1). The electronic balance (PAG114, OHAUS, Ohaus Corp., USA) used to record the weight. The average value was taken by measuring each specimen three times and making a comparison after calculating the average of the three samples. The weight ratios of the various 3D printed longitudinal flatfoot pads were calculated using the weight of the WL structure as the baseline, as it had the least weight compared to other samples, as shown in equation (2). Where T l (sec) represents the total printing time for various lattice samples, and T 0 (sec) represents the total printing time for SL samples. Where W l (g) represents the weight of the various lattice samples, and W 0 (g) represents the weight of the WL samples. In terms of compressive property, the universal mechanical testing machine (AGS-X, Shimadzu, Japan), was used for the compressive test to determine the compressive characteristics of the lattice-structured 3D printed longitudinal flatfoot pads. The compressive properties were measured based on KS M ISO 604. The sample size was 59.03 × 86.64 × 7.06 mm3, and the compression speed was 2.5 mm/min with a load of 5kN. The sample was compressed until it reached its maximum strain at 50%. A stress-strain curve was obtained and the compressive properties of various lattice structures along with different filaments were analyzed. Second, the wearability of the various manufactured 3D printed longitudinal flatfoot pads was evaluated using plantar pressure analysis. The plantar pressure test was performed using a plantar pressure analyzer (Materialise, Belgium) equipped with an 8 m walking path, along with a foot scanner (Alchemaker, Korea), to capture data on plantar pressure and contact area. About subjects, the plantar pressure analysis was proceeded with 10 female participants. Two groups of 5 normal foot (NF) and 5 flatfoot (FF) individuals participated in this research. The subjects were recruited from among the students of Dong-A University. Subjects in the NF were selected as those without any underlying foot disease and no problems walking. About group of FF, subjects were selected based on their prior symptoms of pain or discomfort due to flatfeet. Furthermore, the plantar pressure diagram was confirmed barefoot during static to further verify whether they had FF. The participants had an average age of 24.00 ± 2.98 years, an average height of 158.17 ± 4.51 cm, an average weight of 59.66 ± 4.79 kg, and average foot size of 232.50 ± 6.45 mm. Before the experiment, all participants received detailed information about the study and signed an informed consent form approved by the Institutional Review Board (IRB). This study was approved by Dong-A University’s Institutional Review Board (IRB no. 2-1040709-AB-N-01-202501-HR-003-02). All experiments were performed in accordance with relevant guidelines and regulations. All participants wore identical experimental garments and performed the trials using 3D printed longitudinal flatfoot pads with standardized socks (AWTV003-1, Li-Ning, China). Measurements were taken under various conditions of barefoot (BF), socks (SC), wool pads (WL), and wearing pads. The order of testing was randomized to reduce potential sequence-related bias. Furthermore, plantar pressure was assessed under both static and walking motions. About static motion, plantar force was recorded for 10 seconds while subjects stood upright and faced forward on the pressure analyzer. For static motion, the results for each structure and material were compared through the plantar pressure diagram obtained for 10 seconds. For walking motion, peak plantar pressure of both feet was measured five times each as participants completed five round trips along the walkway, maintaining a pace of 100 bpm with a metronome. The mean values of these repeated trials were used for subsequent analysis. To enhance measurement reliability, all participants practiced three preliminary trials before the actual recordings, and every test was conducted with metronome guidance. A scheme of the experimental method for walking motion is illustrated in Figure 8 (a) . The obtained plantar pressure data were analyzed by peak plantar pressure and contact area of segmented into 10 anatomical zones. The classification table for the 10 zones is shown in Figure 8 (b) . Among these, the meta 1 (M1), meta 3 (M3), and midfoot (MF) zones were emphasized for detailed examination of flatfoot characteristics. And based on peak pressure and contact area, statistical analyses were conducted using SPSS version 26.0 (IBM, USA), with the threshold for significance set at P < 0.05. Plantar pressure distribution was examined through one-way ANOVA based on data collected by both the left and right foot. Especially, attention was given to identifying significant differences relative to the BF condition. Declarations Competing interests The authors declare no competing interests. Reprints and permissions information is available at www.nature.com/reprints . Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons License, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons License, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons License and your intended use is not permitted by statutory regulation or exceed the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ . Funding This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government(MSIT)(No. RS-2023–00272281). Author Contribution S.L. conceived and designed the research; D.C. proceed 3D printing process, characterization of 3D printed longitudinal flatfoot pads, and wrote the manuscript; I.J. proceed characterization of plantar pressure analysis and wrote the manuscript; S.L. developed the method, and provided feedback on the experimental and results and discussion. All authors have reviewed the manuscript, and have agreed to its submission. Acknowledgement This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government(MSIT)(No. RS-2023–00272281). Data Availability The datasets used and/or analyzed during the current study available from the corresponding author S. Lee ( [email protected] ) on reasonable request. References Chen, H., Zhang, Q. & Biró, I. 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16:40:45","extension":"png","order_by":17,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":223550,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-8276506/v1/4fe1e9b87a27ad2fb09c98af.png"},{"id":98037103,"identity":"cc4ec620-9df4-4556-b118-ebe06f0f1abb","added_by":"auto","created_at":"2025-12-12 06:24:17","extension":"png","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":24257,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-8276506/v1/09f8c098a21b155a229a9773.png"},{"id":98037113,"identity":"91085e56-610a-4d22-aaec-bdb1471c9e46","added_by":"auto","created_at":"2025-12-12 06:24:18","extension":"xml","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":144752,"visible":true,"origin":"","legend":"","description":"","filename":"4721043882df4c0ca27a287ae95b4bb71structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8276506/v1/a7ec2aed6b4e860efc54165f.xml"},{"id":98426943,"identity":"e2db632c-9e3e-4499-adf3-e4e2c333595f","added_by":"auto","created_at":"2025-12-17 16:39:03","extension":"html","order_by":20,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":161718,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8276506/v1/d0b178bd2da4160bffde8b13.html"},{"id":98037108,"identity":"2215008a-a6e8-49cc-b0fb-bd345c0bb464","added_by":"auto","created_at":"2025-12-12 06:24:18","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":562605,"visible":true,"origin":"","legend":"\u003cp\u003e(a) First and 1/4th layers of longitudinal flatfoot pads applied various lattice structured. (b) Morphology of 3D printed longitudinal flatfoot pads applied various lattice structure and different filaments.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8276506/v1/39066b16337f469561d349a8.jpeg"},{"id":98037102,"identity":"9c4dba07-41ce-4c75-a3b4-5d9b384f267d","added_by":"auto","created_at":"2025-12-12 06:24:17","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":39995,"visible":true,"origin":"","legend":"\u003cp\u003eTime and weight ratios of 3D printed longitudinal flatfoot pads applied various lattice structure and filament.\u003cstrong\u003e \u003c/strong\u003e(a) Ratio of time. (b) Ratio of weight.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8276506/v1/10f4f9ff0d42746f732770db.jpeg"},{"id":98037106,"identity":"f076adb4-9359-4cde-8b5b-c711cf194219","added_by":"auto","created_at":"2025-12-12 06:24:17","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":187296,"visible":true,"origin":"","legend":"\u003cp\u003eS-S curves and compressive properties of the 3D printed longitudinal flatfoot pads applied various lattice structure and filament. (a) S-S curve of 3D printed longitudinal flatfoot pads using TPU. (b) S-S curve of 3D printed longitudinal flatfoot pads using LW-TPU. (c) S-S curve of 3D printed longitudinal flatfoot pads using LW-PLA. (d) Compressive initial modulus. (e) Compressive stress at 15% strain. (f) Compressive toughness.\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8276506/v1/c52daef2f177561379c5cb61.jpeg"},{"id":98427962,"identity":"4b2b0332-70b9-448e-9193-fd436462e02f","added_by":"auto","created_at":"2025-12-17 16:41:26","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":367674,"visible":true,"origin":"","legend":"\u003cp\u003ePlantar force diagram during static motion. (a) NF. (b) FF.\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8276506/v1/4d8cadd54839c046deacac6a.jpeg"},{"id":98037110,"identity":"0194af58-430d-4ca6-b2ff-7a1fb8282c13","added_by":"auto","created_at":"2025-12-12 06:24:18","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":158728,"visible":true,"origin":"","legend":"\u003cp\u003ePlantar peak pressure of M1, M3, and MF zones with various material and structure during walking motion. (a) NF. (b) FF.\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8276506/v1/0b83d58d76aa243a52121e3b.jpeg"},{"id":98037122,"identity":"b4e5dde4-1e04-4ca0-82bf-de14fa8b3b92","added_by":"auto","created_at":"2025-12-12 06:24:18","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":153262,"visible":true,"origin":"","legend":"\u003cp\u003eContact area of M1, M3, and MF zones with various material and structure during walking motion. (a) NF. (b) FF.\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8276506/v1/5cf2dd0d7f720672eeac8645.jpeg"},{"id":98427145,"identity":"220f7551-5055-489a-a789-8c8f1fab390e","added_by":"auto","created_at":"2025-12-17 16:39:45","extension":"jpeg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":444383,"visible":true,"origin":"","legend":"\u003cp\u003e(a) 3D printing process of thelongitudinal flatfoot pads. (b) Slicing of various lattice structures for 3D printed longitudinal flatfoot pads.\u003c/p\u003e","description":"","filename":"floatimage7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8276506/v1/ba7aeb847adb83a898ac57aa.jpeg"},{"id":98037105,"identity":"853e61a3-c1c5-486a-b5da-d81ea107de51","added_by":"auto","created_at":"2025-12-12 06:24:17","extension":"jpeg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":66088,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Scheme of plantar pressure analysis. (b) 10 zones classification diagram of the sole of the foot.\u003c/p\u003e","description":"","filename":"floatimage8.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8276506/v1/ffddfe7bbbe3880540da3c38.jpeg"},{"id":100614521,"identity":"1f705e12-e7c1-4cee-95af-a02d5de5135b","added_by":"auto","created_at":"2026-01-19 17:21:31","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3007649,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8276506/v1/8d77ecaf-4719-4680-9ebe-9cc903c00b17.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Analysis of 3D printed Longitudinal Flatfoot Pads with Lattice Structures using Various Microfoaming Filament ","fulltext":[{"header":"Introduction","content":"\u003cp\u003eFlatfoot known as pes planus, is a condition in which the medial longitudinal arch collapses, giving the sole a flattened appearance during standing. This deformity alters normal biomechanics, often causing rearfoot eversion, forefoot abduction and excessive inward rolling of the foot\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. A common issue is plantar fascia pain, resulting from excessive stress on the thick tissue along the bottom of the foot. The instability of flatfoot can lead to uneven weight distribution, affecting posture and gait, and causing secondary problems such as knee, hip, or lower back pain\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Treatment often involves approaches to reduce pain, improve performance and prevent further issues, with orthotic devices like custom insoles offering arch support and better weight distribution\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. To evaluate their effectiveness plantar pressure analysis is widely used by measuring the dynamic and static foot pressures, it serves as a key indicator of foot function and is widely used to assess footwear, orthotics and gait training. Recently, pressure-sensing fiber-based wearable devices have been applied to rehabilitation assistance and plantar pressure monitoring, and research has also been reported that simultaneously implements high sensitivity and a wide detection range\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. This analysis reveals how pressure distribution changes after orthotic intervention, offering valuable insights for managing flat feet\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eTo manage the complications arising from flatfoot, orthotic devices such as custom-made foot pads are used. These are traditionally made from materials such as wool, polyurethane, silicone, or gel\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e, but with 3D printing, especially fused deposition modeling (FDM), highly personalized designs have become possible\u003csup\u003e\u003cspan additionalcitationids=\"CR14 CR15 CR16 CR17\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. FDM offers precise control of geometry and distribution, enabling structures with strength, shock absorption, insulation, and vibration damping\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e, making it widely used for customized orthotic pads in various forms like oval, circular, U-shaped, longitudinal and arch-supporting, to improve comfort, alignment, and performance\u003csup\u003e\u003cspan additionalcitationids=\"CR22 CR23 CR24 CR25\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. When customizing 3D printed orthotic pads, the choice of material and structure is crucial for ensuring processability, durability, shock absorption and flexibility. Commonly used materials with these factors are polylactic acid (PLA) and thermoplastic polyurethane (TPU), which are suitable for both rigid and flexible applications due to their versatility\u003csup\u003e\u003cspan additionalcitationids=\"CR28 CR29 CR30 CR31\" citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. Recently, lightweight PLA (LW-PLA) and lightweight TPU (LW-TPU) have gained attention, due to their microcellular structures that reduce density while maintaining consistency, energy absorption, impact resistance and flexibility, applicable for industrial and biomedical uses\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. Beyond materials, structural design is equally important to ensure strength and flexibility in orthotic pads. Lattice structures with lightweight frameworks of interconnected struts, provide high strength with minimal material use and can be modified for strength, flexibility or impact resistance\u003csup\u003e\u003cspan additionalcitationids=\"CR36 CR37 CR38\" citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e. Their adaptability makes them valuable in medical implants, footwear and sports, where performance and durability are essential\u003csup\u003e\u003cspan additionalcitationids=\"CR41 CR42 CR43 CR44\" citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003ePrevious research has analyzed the use of lightweight TPU in footwear applications through FDM 3D printing. Customized outsole designs with varying star-shaped (3-, 4- and 6- pointed) patterns and thicknesses (5, 7.5, 10 mm) were tested for density and rigidity, with the LW 3PS-10 prototype demonstrating superior durability and safety while maintaining comfort across other variations\u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e. Similarly, comparative studies of wool felt and 3D-printed TPU foot correction pads revealed that although TPU pads were slightly heavier due to higher density, they provided enhanced durability, support, and shock absorption\u003csup\u003e\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e. Together, these findings highlight the potential of a 3D printed customized pads as a long-lasting and high-performance material for foot support and comfort.\u003c/p\u003e\u003cp\u003eThis research aimed to improve the medial arch support and redistribute plantar pressure in the midfoot of individuals with flatfoot, by developing and evaluating 3D printed longitudinal flatfoot pads using lattice and solid (SL) structures fabricated with lightweight 3D printing filaments. The pads were first analyzed in terms of morphology and compression properties. Based on these results, two lattice structures were selected for further evaluation under both static and walking using plantar pressure analysis, which evaluated foot pressure distribution. The findings from all the three analysis were then compared to identify the most suitable lattice structure and material combination for effective orthotic applications that enhance comfort and promote proper foot alignment in daily footwear.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cp\u003e\u003cb\u003eMorphology of 3D printed longitudinal flatfoot pads applied various lattice structure and filament.\u003c/b\u003e As observed in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e \u003cb\u003e(a)\u003c/b\u003e, each lattice structure displayed distinct characteristics. The nozzle movements of the first layer were analyzed for each lattice structure to gain a better understanding of the denseness of the lattices. The ICO-H strut unit, closed on all sides, was compact with minimal gaps, forming tightly packed triangular struts into hexagonal cells. It was among the stiffest lattices, requiring 13,302\u0026thinsp;\u0026minus;\u0026thinsp;13,458 nozzle movements. The RHM structure, with intersecting rectangles and open ends, produced dense layers and showed 19,195\u0026thinsp;\u0026minus;\u0026thinsp;19,617 nozzle movements, making it one of the densest designs\u003csup\u003e\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e, \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e. KGM, with closed but small struts and open spacing, formed porous hexagonal cells and required only 7,337-7,552 movements. TET-H, similar to RHM but with slight gaps, showed intermediate density with 13,914\u0026thinsp;\u0026minus;\u0026thinsp;14,466 movements. VOR, resembling KGM but with the most open spacing and prominent hexagonal gaps, exhibited high porosity and low nozzle movements of 7,371-7,551\u003csup\u003e50, 51\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe analysis indicated that nozzle path values correlate with the structural characteristics of the lattices. ICO-H and RHM were identified as the stiffest and densest structures with ICO-H having the intricate high-density geometry resulted in consistently high nozzle movements, while RHM exhibited the greatest inconsistency with the highest overall counts. In contrast, TET-H demonstrated an intermediate density, whereas KGM and VOR with their larger gaps between struts, displayed greater porosity and lower nozzle movements.\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e \u003cb\u003e(b)\u003c/b\u003e shows the morphology and thickness variations of 3D printed longitudinal flatfoot pads using different filaments. As seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb, TPU samples had clear, smooth surfaces without microfoaming, while LW-TPU and LW-PLA exhibited rough, foamed surfaces, consistent with previous findings\u003csup\u003e\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e, \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e. Among LW-PLA samples, ICO-H_LW-PLA showed the highest wall thickness of 2.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05 mm, whereas VOR_LW-PLA had the lowest of 0.93\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 mm. In LW-TPU, ICO-H again displayed the highest thickness, with VOR the lowest, ICO-H_LW-TPU reached 2.19\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03 mm, exceeding ICO-H_LW-PLA due to stronger foaming. For TPU, ICO-H maintained the highest thickness across lattices, while RHM_TPU recorded the lowest of 0.66\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 mm.\u003c/p\u003e\u003cp\u003eThe morphology and wall thickness of the 3D printed longitudinal flatfoot pads depended on both filament type and lattice structures. TPU showed smooth surfaces, while LW-TPU and LW-PLA exhibited microfoaming. ICO-H lattices consistently had the greatest thickness, with ICO-H_LW-TPU being the thickest, and VOR and RHM_TPU the thinnest. These findings demonstrate that filament choice and lattice design critically affect the structural properties of the 3D printed longitudinal flatfoot pads.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eRatio analysis of time and weight of 3D printed longitudinal flatfoot pads applied various lattice structure and filament.\u003c/b\u003e Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e \u003cb\u003e(a)\u003c/b\u003e shows the time ratio of all lattice structures. It was observed that ICO-H showed the highest printing time, while VOR had the least for both left and right lattices. ICO-H_L took 5 h 25 m 26 s, the longest, due to its closely packed and ordered unit cells, while ICO-H_R required 5 h 20 m 21 s. RHM structures also showed longer times because of high density. TET-H and KGM took less time since their unit cells were less dense. VOR structures were the fastest at around 2 h 40 m 49 s, owing to open, less compact unit cells that made printing more efficient\u003csup\u003e\u003cspan additionalcitationids=\"CR55\" citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e \u003cb\u003e(b)\u003c/b\u003e shows the weight ratio of the 3D printed longitudinal flatfoot pads with various lattice structures at 10% infill density, produced using different filaments. It was seen that ICO-H has the highest weight and VOR has the lowest weight for both left and right lattices. Similar to ICO-H, RHM structures also have the higher weight. While the weights in the TET-H and KGM structures were more similar and while the SL and WL structures also showed nearly similar weights, except for SL_LW-PLA. The VOR structure had the least weight. This lighter weight was due to their less dense and less packed unit cell structures compared to others, where it was seen that VOR_TPU had the lowest weight of 5.96\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10 g, while ICO-H_LW-PLA had the highest weight of 13.86\u0026thinsp;\u0026plusmn;\u0026thinsp;0.32 g\u003csup\u003e57, 58\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eTherefore, it was observed that printing time and weight strongly depended on lattice complexity, denser patterns take longer to print and weigh more, while simpler ones print faster and weigh less. Small variations within samples were due to Carbon\u0026rsquo;s design engine, which generated slightly different left and right lattice geometries despite identical sample sizes.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eCompressive property of 3D printed longitudinal flatfoot pads applied various lattice structure and filament.\u003c/b\u003e Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e illustrates the S-S characteristics and compressive properties of five lattice-structured 3D-printed longitudinal flatfoot pads with different filaments.\u003c/p\u003e\u003cp\u003eIn Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e \u003cb\u003e(a-c)\u003c/b\u003e, TPU showed high strength with minimal deformation, LW-TPU balanced compressive stress with higher elongation, and LW-PLA displayed the steepest curve with the highest compressive stress at low strain, indicating easy deformation under stress. ICO-H_LW-PLA had the highest compressive initial modulus of 5.23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.26 MPa, while VOR_TPU had the lowest of 0.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01 MPa among the lattice structures. In comparison, WL_TPU and SL_TPU showed the overall lowest values, with 0.00\u0026thinsp;\u0026plusmn;\u0026thinsp;0.00 MPa and 0.01\u0026thinsp;\u0026plusmn;\u0026thinsp;0.00 MPa, respectively, among all the structures. Compressive stress decreased in the order RHM\u0026thinsp;\u0026gt;\u0026thinsp;KGM\u0026thinsp;\u0026gt;\u0026thinsp;TET-H\u0026thinsp;\u0026gt;\u0026thinsp;SL\u0026thinsp;\u0026gt;\u0026thinsp;WL, among filaments, TPU showed the lowest compressive stress and LW-PLA the highest. In Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e \u003cb\u003e(d-f)\u003c/b\u003e, WL and SL showed the lowest compressive values among all materials and structures. TPU exhibited the lowest compressive properties but higher than WL, LW-TPU demonstrated the highest toughness and LW-PLA displayed the highest initial modulus and stress at 15%, indicating high strength but low toughness. ICO-H_LW-TPU recorded a compressive initial modulus of 0.28\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 MPa, compressive stress of 0.08\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11 kN at 15% strain, and the highest toughness of 7.58\u0026thinsp;\u0026plusmn;\u0026thinsp;0.45 J. VOR_LW-TPU had the lowest compressive initial modulus of 0.09\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01 MPa and compressive stress of 0.13\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01 kN, while TET-H showed the lowest toughness of 2.38\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 J. Among lattice designs, ICO-H provides the greatest strength and stiffness, while VOR is the most flexible and porous, with RHM, KGM, and TET-H in between\u003csup\u003e\u003cspan additionalcitationids=\"CR60 CR61 CR62\" citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eTherefore, it is observed that LW-TPU structures showed moderate compressive stress and higher toughness indicating good strength, exceptional energy absorption, and strong resistance to deformation. In terms of the lattice structures, ICO-H lattice had the highest initial modulus and high compressive stress exhibiting it as the most superior lattice structure in terms of strength and stiffness. On the other hand, VOR variants showed high flexibility but low strength, and TET-H exhibited the lowest toughness, reflecting minimal resistance to deformation. Observing the results of compressive analysis, SL, VOR and ICO-H structures were used forward to analyze the plantar pressure test.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eThermal properties of various filament for 3D printing\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePLA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eLW-PLA\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eTPU\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eLW-TPU\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e\u003cb\u003e1st\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eT\u003c/b\u003e\u003csub\u003e\u003cb\u003eg\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(℃)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e64.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e63.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e77.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e69.18\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eT\u003c/b\u003e\u003csub\u003e\u003cb\u003ec\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(℃)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e114.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e117.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eT\u003c/b\u003e\u003csub\u003e\u003cb\u003em\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(℃)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e148.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e152.16 / 193.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e226.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e159.70 / 194.37\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e∆ H (J/g)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e23.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e23.43 / 0.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e11.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.47 / 0.49\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e\u003cb\u003e2nd\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eT\u003c/b\u003e\u003csub\u003e\u003cb\u003eg\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(℃)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eT\u003c/b\u003e\u003csub\u003e\u003cb\u003ec\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(℃)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e88.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e53.49\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eT\u003c/b\u003e\u003csub\u003e\u003cb\u003em\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(℃)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e∆ H (J/g)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e\u003cb\u003e3rd\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eT\u003c/b\u003e\u003csub\u003e\u003cb\u003eg\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(℃)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e47.63\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e46.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e156.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e129.84\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eT\u003c/b\u003e\u003csub\u003e\u003cb\u003ec\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(℃)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e114.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eT\u003c/b\u003e\u003csub\u003e\u003cb\u003em\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(℃)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e138.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e143.87\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e189.77\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e∆ H (J/g)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eStatic motion plantar pressure analysis of 3D printed longitudinal flatfoot pads applied three types of lattice structure and filament.\u003c/b\u003e Plantar pressure analysis was conducted to evaluate the wearability of the 3D printed longitudinal flatfoot pads according to its material and design. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e indicates zone classification and plantar pressure diagrams in a static motion during wearing 3D printed longitudinal flatfoot pads. Based on the results of the characteristic analysis of 3D printed longitudinal pads, two lattice structures were selected and analyzed. VOR, which had the lowest density among the lattice structures, and ICO-H, which had high density and therefore high strength.\u003c/p\u003e\u003cp\u003eAs shown as Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, in the NF, pressure was primarily concentrated at the heel and forefoot, with relatively low values observed in the MF region, forming a typical two-peak support pattern. Across the shoe conditions, BF and SC exhibited distinct heel and forefoot loading. Including wool (WL) condition, wearing 3D printed pads status showed a broader contact area with partial pressure redistribution. For the 3D printed longitudinal flatfoot pads, TPU, LW-TPU, and LW-PLA demonstrated material-dependent differences. In particular, LW-PLA maintained relatively localized forefoot pressures and reduced pressure for heel.\u003c/p\u003e\u003cp\u003eIn contrast, the FF revealed a markedly different pressure distribution compared to NF. Due to arch collapse, high pressure was consistently detected in the all regions and had broad contact area in MF region. Thus, it was confirmed that a three-point support pattern was involved the heel, midfoot, and forefoot. BF status showed a distinct concentration of pressure in the midfoot, clearly differentiating flatfoot from the NF. And while WL demonstrated extended pressure coverage, it failed to sufficiently relieve MF loading, resulting in increased pressure in the forefoot area. Among the 3D printed longitudinal flatfoot pads conditions, as the area of the MF appears to be wider, it was confirmed providing arch support. By materials, while TPU and LW-TPU presented high forefoot pressures, LW-PLA revealed that pressure concentration in the forefoot and midfoot was decreased. And in particular, in both the NF and FF groups, the ICO-H structure was observed to reduce the pressure on the forefoot and heel.\u003c/p\u003e\u003cp\u003eAccordingly, it was confirmed that 3D printed longitudinal flatfoot pads exhibited differences in plantar pressure depending on the material and design. For FF conditions, rigid orthotics have been reported to increase arch height and enhance ankle stability as contributing to pressure redistribution and improved wearing comfort. In particular, in cases of moderate to severe flatfoot or adult-acquired flatfoot with marked deformity or instability, rigid or semi-rigid orthotics have been shown to be effective in providing corrective support\u003csup\u003e\u003cspan additionalcitationids=\"CR65\" citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e\u003c/sup\u003e. Therefore, this study confirmed that the ICO-H longitudinal flatfoot pad made of LW-PLA showed the most effective pressure distribution with relatively mitigated MF pressure and increased contact area during static motion.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eWalking plantar peak pressure analysis of 3D printed longitudinal flatfoot pads with three types of lattice structure and filament.\u003c/b\u003e Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows peak pressure at the M1, M3, and MF zones during walking motion. To determine the differences between NF and FF, this study focused on M1, M3, and MF around the arch.\u003c/p\u003e\u003cp\u003eIn terms of plantar peak pressure during walking motion, the groups of NF and FF showed some difference results. For the NF group, the BF was 10.90\u0026thinsp;\u0026plusmn;\u0026thinsp;2.24 N/cm\u003csup\u003e2\u003c/sup\u003e for M1, 16.96\u0026thinsp;\u0026plusmn;\u0026thinsp;2.50 N/cm\u003csup\u003e2\u003c/sup\u003e for M3, and 7.38\u0026thinsp;\u0026plusmn;\u0026thinsp;2.72 N/cm\u003csup\u003e2\u003c/sup\u003e for MF, respectively. M3 located the center of the forefoot exhibited the highest peak pressure. And when wearing the 3D printed longitudinal pads, peak pressure values were decreased in all zones compared to the BF status. In the M1 zone, peak pressure of ICO-H_LW-PLA was the lowest pressure for 9.24\u0026thinsp;\u0026plusmn;\u0026thinsp;1.83 N/cm\u003csup\u003e2\u003c/sup\u003e. In terms of M3 and MF zone, SL_LW-LA appeared the lowest value as 14.03\u0026thinsp;\u0026plusmn;\u0026thinsp;2.97 N/cm\u003csup\u003e2\u003c/sup\u003e and 6.41\u0026thinsp;\u0026plusmn;\u0026thinsp;1.47 N/cm\u003csup\u003e2\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eFor the FF group, a similar tendency was observed with NF group. The BF status for the FF group were 9.48\u0026thinsp;\u0026plusmn;\u0026thinsp;2.20 N/cm\u003csup\u003e2\u003c/sup\u003e in M1, 14.78\u0026thinsp;\u0026plusmn;\u0026thinsp;3.18 N/cm\u003csup\u003e2\u003c/sup\u003e for M3, and 8.22\u0026thinsp;\u0026plusmn;\u0026thinsp;2.18 N/cm\u003csup\u003e2\u003c/sup\u003e for MF, respectively. Compared to the NF group, as the pressures in M1 and M3 decreased, the pressure in the MF zone increased. It indicated that the collapse of the arch led to a greater load and increased pressure load in the MF zone. In the M1 and MF zones, wearing the 3D printed longitudinal pads resulted in a decrease in peak pressure compared to the BF zone. Conversely, in the M3 zone, the values were generally higher. This phenomenon can be attributed to the redistribution of force toward the medial arch, where the pads provided support. Also, similar to the NF group, ICO-H_LW-TPU exhibited the greatest peak pressure reduction in M1 for 8.21\u0026thinsp;\u0026plusmn;\u0026thinsp;2.38 N/cm\u003csup\u003e2\u003c/sup\u003e, while SL_LW-PLA showed the greatest peak pressure reduction for 13.82\u0026thinsp;\u0026plusmn;\u0026thinsp;3.27 N/cm\u003csup\u003e2\u003c/sup\u003e and 7.28\u0026thinsp;\u0026plusmn;\u0026thinsp;1.14 N/cm\u003csup\u003e2\u003c/sup\u003e in M3 and MF.\u003c/p\u003e\u003cp\u003eRegarding the compressive properties, SL_LW-PLA was found to be the higher strength than all TPU and LW-TPU pads. However, when compressed above 10%, it showed the lowest strength among LW-PLA pads. Furthermore, in the M1 and M3 zones, LW-PLA pads were found to be able to reduce plantar pressure. Whereas in MF, VOR_LW-PLA and ICO-H_LW-PLA showed increased peak pressures of 7.75\u0026thinsp;\u0026plusmn;\u0026thinsp;1.15 N/cm\u003csup\u003e2\u003c/sup\u003e and 7.83\u0026thinsp;\u0026plusmn;\u0026thinsp;1.46 N/cm\u003csup\u003e2\u003c/sup\u003e, respectively. Some studies have reported that while high-rigidity flatfoot orthotics can increase the arch height. However, excessive rigidity can increase plantar peak pressure and foot fatigue\u003csup\u003e\u003cspan additionalcitationids=\"CR67\" citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e\u003c/sup\u003e. Accordingly, ICO-H_LW-PLA was found to be excessively rigid to effectively distribute plantar pressure.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eWalking contact area analysis of 3D printed longitudinal flatfoot pads with three types of lattice structure and filament.\u003c/b\u003e Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e indicates walking motion\u0026rsquo;s contact areas at the M1, M3, and MF zones. For the NF group, contact area of BF was 15.36\u0026thinsp;\u0026plusmn;\u0026thinsp;1.52% in M1, 9.04\u0026thinsp;\u0026plusmn;\u0026thinsp;1.20% in M3, and 21.73\u0026thinsp;\u0026plusmn;\u0026thinsp;4.84% in MF, respectively. Also, when wearing the 3D printed longitudinal pad, the contact area values were found to increase compared to BF. In particular, the contact area in the MF zone of the NF increased from 21.73% to 26.44\u0026ndash;36.08%. The highest contact area values were observed when wearing SL_LW-PLA in M1 for 18.48\u0026thinsp;\u0026plusmn;\u0026thinsp;1.38% and MF for 36.08\u0026thinsp;\u0026plusmn;\u0026thinsp;4.92%, and ICO-H_LW-TPU in M3 for 9.80\u0026thinsp;\u0026plusmn;\u0026thinsp;1.07%. In particular, for the 3D printed longitudinal flatfoot pad made of LW-PLA, SL_LW-PLA, VOR_LW-PLA, and ICO-H_LW-PLA exhibited values of 36.08\u0026thinsp;\u0026plusmn;\u0026thinsp;4.92%, 35.04\u0026thinsp;\u0026plusmn;\u0026thinsp;4.76%, and 34.37\u0026thinsp;\u0026plusmn;\u0026thinsp;5.23%, respectively, representing substantial increases of approximately 58\u0026ndash;66%. It demonstrated a redistribution of plantar pressure toward the arch. Also, in all zone, significant differences were confirmed as both material and lattice structure can affect contact area during gait. In the FF group, FF had a larger contact area overall, especially in the arch-related M1 and MF zones compared to NF group. Also, as FF had the collapsed arch and broader plantar coverage, no significant effect was observed in the M3 zone though the differences compared to other pads were less resulted than in NF group. In the M1 zone, SL_LW-PLA and VR_LW-PLA exhibited the largest contact area as 20.02\u0026thinsp;\u0026plusmn;\u0026thinsp;2.09% and 20.05\u0026thinsp;\u0026plusmn;\u0026thinsp;2.02% compared to BF status as 19.14\u0026thinsp;\u0026plusmn;\u0026thinsp;2.10%. Especially, in MF zone, BF status already appeared high contact area for 33. 09\u0026thinsp;\u0026plusmn;\u0026thinsp;2.89%. It increased to over 40% in SL_LW-PLA for 42.05\u0026thinsp;\u0026plusmn;\u0026thinsp;4.05%, VR_LW-PLA for 40.29\u0026thinsp;\u0026plusmn;\u0026thinsp;5.32%, and IC_LW-PLA 40.32\u0026thinsp;\u0026plusmn;\u0026thinsp;5.01%. And statistical analysis confirmed significant differences in the M3 and MF zones, while the difference was not significant in M1 zone as p value for 0.122.\u003c/p\u003e\u003cp\u003eThus, these results indicated that contact area expansion was more pronounced in the MF zone, especially in FF where the collapse of the arch inherently increased plantar pressure in MF. And the 3D printed longitudinal flatfoot pads made of LW-PLA were most effective in enlarging the contact area and pressure distribution. In addition, wearing 3D printed longitudinal flatfoot pads can improve arch support as increasing contact area with balancing the contributions with the moderate increases in M1 and M3.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study aimed to identify the most effective materials and design for flatfoot patients by manufacturing a 3D printed longitudinal flatfoot pad. The pads were fabricated using various microfoaming filaments for TPU, LW-TPU, LW-PLA and lattice structures for VOR, TET-H, KGM, RHM, ICO-H. The structural characteristics of modeling, output efficiency, compressive properties, and improvement of plantar pressure distribution were comprehensively analyzed. The results confirmed that the composite materials and structural design significantly impacted arch support and pressure distribution in patients with flatfoot.\u003c/p\u003e\u003cp\u003eAs results of 3D printed longitudinal flatfoot pads, morphological and compressive properties revealed that ICO-H lattice structured with high density exhibited superior strength, whereas VOR provided higher flexibility with reduced strength. These mechanical properties contributed to plantar pressure responses during both static and walking motions. For plantar pressure analysis, under static motion, pad LW-PLA applied ICO-H effectively reduced MF pressure with enlarging contact area. Thereby it can provide enhanced arch support compared to BF and WL. During walking motion, peak plantar pressures were reduced across the M1, M3, and MF zones when wearing 3D printed longitudinal flatfoot pads. Furthermore, contact area analyses confirmed that LW-PLA pads substantially increased MF zones by up to 66% in NF and exceeding 40% in FF. Thus, it was confirmed that 3D printed longitudinal flatfoot pads with LW-PLA improved pressure redistribution toward the arch.\u003c/p\u003e\u003cp\u003eTherefore, this study reported that lattice structured pads fabricated with LW filaments can provide functional improvements over conventional pads. Specifically, the SL and ICO-H designs combined with LW-PLA achieved an optimal balance between stiffness and flexibility, ensuring both effective pressure reduction and increased contact area expansion. These results can suggest that 3D printed lattice based flatfoot pads are a promising solution for flatfoot treatment as offering enhances arch stability, reduces localized load, and enhances comfort during everyday walking activities. In future research, this study will be utilized as fundamental data to conduct customized modeling based on individual patient foot data and to apply different designs by region in order to identify more effective modeling strategies for flatfoot.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eMaterials.\u0026nbsp;\u003c/strong\u003eTo manufacture the 3D printed longitudinal flatfoot pads, three types of filaments of thermoplastic polyurethane (eflex, Esun Co. Ltd., China), lightweight thermoplastic polyurethane (Varioshore TPU, ColorFabb, Netherlands) and lightweight polylactic acid (LW-PLA, ColorFabb, Netherlands) filaments with a diameter of 1.75 mm were used. 3D printing was conducted using an FDM technique with a 3D printer (Cubicon single plus, Cubicon Co. Ltd., Korea) equipped with a 0.4 mm diameter nozzle.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSample preparation of 3D printed longitudinal flatfoot pads.\u003c/strong\u003e \u003cstrong\u003eFigure 7 (a)\u003c/strong\u003e shows the modeling, slicing and 3D printed longitudinal flatfoot pads with a size of 59.03 \u0026times;86.64 \u0026times;7.06 mm\u0026sup3; using design engine (Carbon, USA). The 3D model of the longitudinal flatfoot pads were saved in *.stl files. The slicing of the 3D printed longitudinal flat foot pads. Slicing was performed using the Cubicreator4 V4.4.0 slicing program (Cubicon Co. Ltd., Korea) under the following conditions, nozzle temperatures of 230 ℃ for TPU and LW_PLA filaments and 240 ℃ for LW-TPU filaments, a bed temperature of 65 ℃ for the LW-PLA filaments and room temperature for TPU and LW-TPU filaments, a printing speed of 60 mm/sec, infill pattern of zigzag and 10% infill density. *.stl files were converted into printable *.g-code files within the slicing program. The longitudinal flatfoot pads were manufactured using a solid (SL) structure and five different lattice structures and their mechanical properties were further compared with those of a wool (WL) pad.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFigure 7 (b)\u0026nbsp;\u003c/strong\u003eshows the detailed lattice structures of five different lattices, i.e., voronoi (VOR), tetrahedral (TET-H), kagome (KGM), rhombic (RHM) and icosahedral (ICO-H) using the design engine. Firstly, in the modeling program, the strut lattices were set and was solidified, and the 3D model of the longitudinal arch pads was saved in *.stl files. The *.stl files were uploaded in the slicing program, the 3D printed conditions were set and *.stl files were converted into printable *.g-code files within the slicing program. As all the samples were of the same size, the samples consisted of a total of 39 layers, including 3 layers of the inner wall and 3 layers of the outer wall, with the rest being infill layers.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCharacterization.\u0026nbsp;\u003c/strong\u003eIn this study, a 3D printed longitudinal flatfoot pad and its wearability were evaluated.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eFirst, the characterization of the 3D printed longitudinal flatfoot pad was conducted as follows. In case of morphology, microscope (NTZ-6000, Nextecvision Co. Ltd., Korea) was used to check the morphology of the various lattice structures of the 3D printed longitudinal flatfoot pads using various filaments. The magnification used was \u0026times;4.55 to check the cell wall thickness of the samples. About ratio of time and weight, the time was recorded with the help of the display on the 3D printer (Cubicon Inc., Republic of Korea). The time ratios of the various 3D printed longitudinal flatfoot pads were calculated using the total printing time of the SL lattice structure as the baseline, as it required the least printing time, as shown in equation (1). The electronic balance (PAG114, OHAUS, Ohaus Corp., USA) used to record the weight. The average value was taken by measuring each specimen three times and making a comparison after calculating the average of the three samples. The weight ratios of the various 3D printed longitudinal flatfoot pads were calculated using the weight of the WL structure as the baseline, as it had the least weight compared to other samples, as shown in equation (2).\u003c/p\u003e\n\u003cp\u003e\u003cimg src=\"data:image/png;base64,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\" width=\"597\" height=\"52\"\u003e\u003c/p\u003e\n\u003cp\u003eWhere T\u003csub\u003el\u003c/sub\u003e (sec) represents the total printing time for various lattice samples, and T\u003csub\u003e0\u003c/sub\u003e (sec) represents the total printing time for SL samples.\u003c/p\u003e\n\u003cp\u003e\u003cimg src=\"data:image/png;base64,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\" width=\"580\" height=\"51\"\u003e\u003c/p\u003e\n\u003cp\u003eWhere W\u003csub\u003el\u003c/sub\u003e (g) represents the weight of the various lattice samples, and W\u003csub\u003e0\u003c/sub\u003e (g) represents the weight of the WL samples.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn terms of compressive property, the universal mechanical testing machine (AGS-X, Shimadzu, Japan), was used for the compressive test to determine the compressive characteristics of the lattice-structured 3D printed longitudinal flatfoot pads. The compressive properties were measured based on KS M ISO 604. The sample size was 59.03 \u0026times; 86.64 \u0026times; 7.06 mm3, and the compression speed was 2.5 mm/min with a load of 5kN. The sample was compressed until it reached its maximum strain at 50%. A stress-strain curve was obtained and the compressive properties of various lattice structures along with different filaments were analyzed.\u003c/p\u003e\n\u003cp\u003eSecond, the wearability of the various manufactured 3D printed longitudinal flatfoot pads was evaluated using plantar pressure analysis. The plantar pressure test was performed using a plantar pressure analyzer (Materialise, Belgium) equipped with an 8 m walking path, along with a foot scanner (Alchemaker, Korea), to capture data on plantar pressure and contact area. About subjects, the plantar pressure analysis was proceeded with 10 female participants. Two groups of 5 normal foot (NF) and 5 flatfoot (FF) individuals participated in this research. The subjects were recruited from among the students of Dong-A University. Subjects in the NF were selected as those without any underlying foot disease and no problems walking. About group of FF, subjects were selected based on their prior symptoms of pain or discomfort due to flatfeet. Furthermore, the plantar pressure diagram was confirmed barefoot during static to further verify whether they had FF. The participants had an average age of 24.00 \u0026plusmn; 2.98 years, an average height of 158.17 \u0026plusmn; 4.51 cm, an average weight of 59.66 \u0026plusmn; 4.79 kg, and average foot size of 232.50 \u0026plusmn; 6.45 mm. Before the experiment, all participants received detailed information about the study and signed an informed consent form approved by the Institutional Review Board (IRB). This study was approved by Dong-A University\u0026rsquo;s Institutional Review Board (IRB no. 2-1040709-AB-N-01-202501-HR-003-02). All experiments were performed in accordance with relevant guidelines and regulations.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAll participants wore identical experimental garments and performed the trials using 3D printed longitudinal flatfoot pads with standardized socks (AWTV003-1, Li-Ning, China). Measurements were taken under various conditions of barefoot (BF), socks (SC), wool pads (WL), and wearing pads. The order of testing was randomized to reduce potential sequence-related bias. Furthermore, plantar pressure was assessed under both static and walking motions. About static motion, plantar force was recorded for 10 seconds while subjects stood upright and faced forward on the pressure analyzer. For static motion, the results for each structure and material were compared through the plantar pressure diagram obtained for 10 seconds. For walking motion, peak plantar pressure of both feet was measured five times each as participants completed five round trips along the walkway, maintaining a pace of 100 bpm with a metronome. The mean values of these repeated trials were used for subsequent analysis. To enhance measurement reliability, all participants practiced three preliminary trials before the actual recordings, and every test was conducted with metronome guidance. A scheme of the experimental method for walking motion is illustrated in \u003cstrong\u003eFigure 8 (a)\u003c/strong\u003e. The obtained plantar pressure data were analyzed by peak plantar pressure and contact area of segmented into 10 anatomical zones. The classification table for the 10 zones is shown in \u003cstrong\u003eFigure 8 (b)\u003c/strong\u003e. Among these, the meta 1 (M1), meta 3 (M3), and midfoot (MF) zones were emphasized for detailed examination of flatfoot characteristics. And based on peak pressure and contact area, statistical analyses were conducted using SPSS version 26.0 (IBM, USA), with the threshold for significance set at P \u0026lt; 0.05. Plantar pressure distribution was examined through one-way ANOVA based on data collected by both the left and right foot. Especially, attention was given to identifying significant differences relative to the BF condition.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eCompeting interests\u003c/h2\u003e\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003ch2\u003eReprints and permissions information\u003c/h2\u003e\u003cp\u003eis available at \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ewww.nature.com/reprints\u003c/span\u003e\u003cspan address=\"http://www.nature.com/reprints\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003ch2\u003eOpen Access\u003c/h2\u003e\u003cp\u003eThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons License, and indicate if changes were made. The images or other third party material in this article are included in the article\u0026rsquo;s Creative Commons License, unless indicated otherwise in a credit line to the material. If material is not included in the article\u0026rsquo;s Creative Commons License and your intended use is not permitted by statutory regulation or exceed the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://creativecommons.org/licenses/by/4.0/\u003c/span\u003e\u003cspan address=\"http://creativecommons.org/licenses/by/4.0/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eThis work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government(MSIT)(No. RS-2023\u0026ndash;00272281).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eS.L. conceived and designed the research; D.C. proceed 3D printing process, characterization of 3D printed longitudinal flatfoot pads, and wrote the manuscript; I.J. proceed characterization of plantar pressure analysis and wrote the manuscript; S.L. developed the method, and provided feedback on the experimental and results and discussion. All authors have reviewed the manuscript, and have agreed to its submission.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThis work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government(MSIT)(No. RS-2023\u0026ndash;00272281).\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used and/or analyzed during the current study available from the corresponding author S. Lee ([email protected]) on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eChen, H., Zhang, Q. \u0026amp; Bir\u0026oacute;, I. Effects of Arch Support Pads and Insoles on Gait Parameters and Plantar Mechanics During Running in Adults with Flatfoot \u003cem\u003eIEEE 7th International Conference and Workshop \u0026Oacute;buda on Electrical and Power\u003c/em\u003e Engineering \u003cem\u003e(CANDO-EPE)\u003c/em\u003e (2024). (2024). 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Eng.\u003c/em\u003e \u003cb\u003e2017\u003c/b\u003e (1), 8614341 (2017).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"3D printed longitudinal flatfoot pads, Fused deposition modeling (FDM) 3D printing, Lattice structure, Foaming materials, Compressive property","lastPublishedDoi":"10.21203/rs.3.rs-8276506/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8276506/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePurpose of this study is to develop longitudinal flatfoot pads using 3D printing technology for support and treatment of the arch. By applying various materials and designs to the pads, the most effective condition was confirmed. The design of the 3D models was inspired by commercially available wool based pads, and fabrication was carried out through fused deposition modeling (FDM) 3D printing. To manufacture products with different hardness levels, five lattice structures (Voronoi, tetrahedral, kagome, rhombic, and icosahedral) as well as a solid structure were applied. For materials, thermoplastic polyurethane (TPU), lightweight thermoplastic polyurethane (LW-TPU) and lightweight polylactic acid (LW-PLA) were used to produce flatfoot pads with various lattice configurations. The manufactured 3D printed longitudinal flatfoot pads were first analyzed in terms of morphology and compressive properties. Subsequently, two selected structures were evaluated under both static standing and walking conditions using plantar pressure analysis to identify the most suitable manufacturing conditions for flatfoot orthotic applications. In conclusion, 3D printed longitudinal flatfoot pads using LW-PLA pads improved contact area and redistributed midfoot pressure, while 3D printed longitudinal flatfoot pads using LW-TPU provided superior outcomes by reducing localized loading and enhancing arch support. Notably, Icosahedral lattices with LW-PLA designs were most effective for arch stabilization.\u003c/p\u003e","manuscriptTitle":"Analysis of 3D printed Longitudinal Flatfoot Pads with Lattice Structures using Various Microfoaming Filament","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-12 06:23:45","doi":"10.21203/rs.3.rs-8276506/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-12-19T06:47:02+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-18T09:27:18+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-16T01:07:03+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"47944432908729685857487757475004486724","date":"2025-12-16T00:38:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"114787866676414455560098869957538028000","date":"2025-12-15T10:18:33+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"246048493923219247950972246693732157327","date":"2025-12-15T09:39:03+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"286209678580760721402645280900557088561","date":"2025-12-10T12:01:50+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-09T02:47:41+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-08T12:53:23+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-12-08T12:00:06+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-05T09:52:41+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-12-05T09:44:00+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b29356df-c723-4611-a4c2-38182a63715e","owner":[],"postedDate":"December 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":59419996,"name":"Physical sciences/Engineering"},{"id":59419998,"name":"Physical sciences/Materials science"}],"tags":[],"updatedAt":"2026-01-19T16:44:41+00:00","versionOfRecord":{"articleIdentity":"rs-8276506","link":"https://doi.org/10.1038/s41598-026-36008-0","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2026-01-12 16:28:25","publishedOnDateReadable":"January 12th, 2026"},"versionCreatedAt":"2025-12-12 06:23:45","video":"","vorDoi":"10.1038/s41598-026-36008-0","vorDoiUrl":"https://doi.org/10.1038/s41598-026-36008-0","workflowStages":[]},"version":"v1","identity":"rs-8276506","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8276506","identity":"rs-8276506","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}