A High-Conductivity and Adhesive Ionogel Strain Sensor for Monitoring Stimulus-Response Behavior of Aquatic Organism

A High-Conductivity and Adhesive Ionogel Strain Sensor for Monitoring Stimulus-Response Behavior of Aquatic Organism | 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 A High-Conductivity and Adhesive Ionogel Strain Sensor for Monitoring Stimulus-Response Behavior of Aquatic Organism Yahui Wen, Xinghai Wang, Jinxue Zhao, Xuejing Zhai, Wei Xia, Peiyi Li, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5757703/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Ionogels have emerged as versatile materials with potential applications in flexible electronics and soft robotics. However, preparing high-performance ionogels with high conductivity and good mechanical strength remains challenging. Here, we report the development of a novel supramolecular ionogel as a wearable device for monitoring the stimulus-response behavior of aquatic animals. The integration of silver nanowires (AgNWs) endows the ionogel with good electrical conductivity (0.56 S m − 1 ) and mechanical robustness (strain tolerance › 1400%). The ionic liquid (IL) makes the AgIL ionogel exhibit superior adhesion properties (84.6 kPa) across diverse substrates, including biological tissues (e.g., pig skin). Furthermore, this wearable electronic exhibit an ultra-low detection limit (0.5%). The wearable electronics device consists of flexible AgIL ionogels as the sensing material, a microcontroller, a signal processing circuit, and a Bluetooth transceiver. Its electrical responsiveness and stable cyclic performance highlight its potential for wearable applications. This device can clearly and continuously monitor the regular or various stimuli-induced movements of the gills, tail, and body of aquatic animals such as the Chinese sturgeon and bullfrog. Comparative studies with traditional rigid ionogels and hydrogels underscore the significant enhancements in flexibility, adhesion, and conductivity by our design. This work provides a pathway for engineering multifunctional gels tailored for next generation soft electronic interfaces and broadens strain sensors' application range. Wearable electronics silver nanowires ionogel high electrical conductivity aquatic organisms stimulus-response behavior Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction The development of flexible 1 – 4 , conductive materials for use in bio-sensing applications has become an area of intense interest due to their potential to monitor biological phenomena in real-time 5 – 12 . Sensors capable of detecting the movements of living organisms 13 – 16 , particularly soft-bodied animals, require materials that combine high electrical conductivity, mechanical flexibility, and strong adhesion to irregular surfaces 17 – 20 . These sensors not only conform closely to the skin, reducing noise and artifacts caused by poor contact, but also collect high-quality data continuously without causing discomfort 21 – 23 . Currently, hydrogel-fabricated sensors are widely used for their superior conductivity and good mechanical stability 24 , 25 . However, the hydrogel contains amount of water contents, which decreases the long-term performance due to its evaporation 26 – 32 . Ionic liquids (ILs), which exhibit low volatility, high chemical stability, and excellent ionic conductivity, have emerged as promising materials for the fabrication of such sensors to overcome their evaporation 33 – 35 . However, conventional ionogels made from ionic liquids and polymers are typically rigid and suffer from low ionic conductivity due to the restrictive crosslinking of polymer chains, limiting their practical applications in flexible sensing 36 – 40 . Furthermore, most existing ionogels still suffer from poor mechanical properties, low conductivity, and high rigidity, which prevent them from tightly adhering to the aquatic organisms and monitoring their movements. To overcome these limitations, we propose a novel ionogel, which integrates silver nanowires (AgNWs) into imidazole-based ionic liquids (IL) 41 . The incorporation of AgNWs facilitates the creation of a robust conductive network, ensuring rapid electron migration and improved sensor performance 42 . This design leverages the dual conductive pathways of ionic and electronic conduction, resulting in significantly enhanced conductivity. It also exhibits high flexibility, low Young’s modulus, and outstanding strain tolerance, making it capable of conforming to soft and complex surfaces, such as the skin of aquatic animals. In addition to its superior electrical and mechanical properties, the AgIL ionogel demonstrates excellent environmental stability, maintaining its functionality over a broad temperature range. Furthermore, the sensor's wireless data transmission capability, coupled with its high sensitivity and stability, enables real-time monitoring of aquatic animals’ physiological states. This is particularly useful in environmental monitoring, where the detection of subtle changes in animal behavior can serve as an indicator of environmental stressors, such as pollution or habitat degradation. Experimental section Material 1-Butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][OTf],97%) and acrylic acid (AA) purchased from Macklin (Shanghai, China). Sodium alginate (SA, 99%), acrylamide (AM, ≥ 99%) N, N’- methylenebis(acrylamide) (BIS, 99%), ammonium persulfate (APS, ≥ 98%), N, N, N’, N’-tetramethyl ethylenediamine (TEMED, 99%), and sodium chloride (NaCl, ≥ 99%) purchased from Sigma Aldrich (Shanghai, China). 3-Ethyl-1-methylimidazolium trifluoromethanesulfonate ([EMIM][OTf], 98%) and silver nanowires (AgNWs, diameter: 60nm, length: 45 µm) purchased from Anpel (Shanghai, China). Preparation of AgIL ionogel As a representative example, AgIL ionogel was prepared by dissolving APS (4.5 mg) and BIS (4.5 mg) in [BMIM][OTf] (2.1 g) using ultrasonic treatment. AgNWs(0.12 g) was then added to the solution and sonicated using an ultrasonic homogenizer to achieve a homogeneous dispersion of AgNWs in the IL. AA (0.9g) was added to this mixture, followed by thoroughly shaking. The resulting solution was poured into a polytetrafluoroethylene (PTFE) mold and cured at 90°C for 8 hours to yield the final AgIL ionogel. For the preparation of a soft [BMIM] ionogel without AgNW, 30AA was synthesized by following the same method. For the preparation of a traditional rigid ionogel, APS and BIS were dissolved in [BMIM][OTf] by ultrasonic treatment.AA was then added, and the mixture was shaken thoroughly. The resulting solution was poured into a PTFE mold and heated at 85°C for 2 hours to yield the final [BMIM][OTf] ionic gel. For the preparation of the SA hydrogel, six solutions—SA (2 mL, 4.8%), AAM (2.75 mL, 19%), APS (70 µL, 0.2 mol L⁻¹), BIS (600 µL, 2 wt.%), TEMED, and NaCl (300 µL, 1 mol L⁻¹) were mixed and cured under 365 nm UV light for 1 hour. BIS, APS, and TEMED acted as the crosslinker, photoinitiator, and crosslinking accelerator, respectively, to form the final SA hydrogel. Mechanical test Mechanical properties of the ionic gels were evaluated using a universal testing machine (ZQ990LB, Chitake, China). Tensile tests were conducted at ambient conditions (25℃, 40% relative humidity) with a 100 N load cell at a constant strain rate of 100 mm/min, unless otherwise stated. Tensile-release tests were carried out under the same conditions with rectangular specimens (30 mm in length, 10 mm in width, and 2 mm in thickness). Cyclic tensile tests were performed using a uniaxial stretching machine at a constant compression rate. All test were repeated at least three times with independent samples. Young's modulus was calculated from the average slope of the stress-strain curve in the strain range of 20–60%. Electrical conductivity test The resistance (R) of the materials was measured using LCR digital bridge tester (EA4980AL, Keysight) and the electrical conductivity (σ) was calculated as follows: \(\:\sigma\:=\frac{L}{R\times\:S}\:\) ……… (1) Where (L) and (S) represent the gauge length and cross-sectional area of the ionic conductor, respectively. The samples were prepared with length of 25 mm, width of 10 mm, and thickness of 2 mm. The relative resistance was measured using an LCR meter. The relative resistance change (ΔR/R₀) of the stretched samples was calculated as follows: $$\:\varDelta\:R/{R}_{0}=\frac{{R}_{t}-{R}_{0}}{{R}_{0}}$$ 2 ……… Where (R t ) and (R 0 ) represent the relative resistance at the stretched and initial states, respectively. The gauge factor (GF) was defined as: $$\:GF=\left(\frac{\varDelta\:R}{{R}_{0}}\right)/\epsilon\:$$ 3 ……… Where (ε) is the applied strain. Adhesion tests Lap-shear measurements were conducted using a general mechanical testing machine. The maximum stress force was divided by the corresponding contact area created by overlapping tissue samples to calculate the stress values. Rectangular slices of pig skin, fish skin, frog skin, and glass (15 mm × 30 mm) were prepared. The AgIL ionogel was prepared in dimensions of 10 mm × 10 mm × 2 mm, with the overlapping area controlled at 10 mm × 10 mm. The lap shear strength of the hydrogel was tested using a mechanical testing machine. Results and Discussion Design and preparation of AgILgel. ILs are a class of fully ionized substances that remain in liquid form at room temperature. Owing to their rich C-F bonds, ILs exhibit low volatility, strong chemical and thermal stability, and hold promising potential for applications in fields such as wearable devices. However, ionogels fabricated from traditional ILs and polymers are typically hindered by a highly crosslinked polymer network, which restricts the mobility of ions within the gel matrix. This results in low conductivity and high rigidity, thereby preventing the gel from conforming to the dynamic movement of the skin. As demonstrated in Fig. 1 a and b, traditional rigid ionogel sensors fail to adapt to surfaces with varying shapes during monitoring, limiting their ability to deform in response to the real-time movements. Consequently, we have developed a flexible ionogel sensor designed for the continuous monitoring of aquatic animals movements, such as fish. This novel ionogel can closely conform to the surface of the soft skin and respond to its movement with corresponding shape alterations. Young's modulus, a measure of the material’s resistance to elastic deformation under stress, serves as an indicator of the ionogel’s softness. Lower Young's modulus values correlate with increased softness, resulting in enhanced adhesion to the soft skin. AgNWs, known for their high electrical conductivity (354 S/cm) and antimicrobial ability, are employed as nanofillers to enhance the conductivity of the ionogel. AgNWs facilitate electron migration within the material, acting as conductive bridges and significantly improving the overall conductivity. The AgILgel was synthesized using a simple “one-pot” method, as illustrated in Fig. 1 c. The unique structure of ILs ensures the structural integrity of the homogeneously dispersed AgNWs (Fig. S1 ), while electrostatic and physical interlocking interactions between the ILs and AgNWs help preserve their electrical properties, further enhancing the conductivity of AgILgel. In addition to its softness, excellent conformability, and rapid deformation response, AgILgel demonstrates superior electrical conductivity compared to traditional ionogels. The conductivity of conventional ionogels depends on the migration of internal ions through these conductive pathways (Fig. 1 d). Upon compression, ion gradients form due to the differential mobilities of anions and cations, generating a voltage signal. In contrast, AgILgel benefits from dual conductive pathways: conventional ionic conduction and electron conduction via AgNWs (Fig. 1 e), resulting in significantly enhanced electrical performance. Moreover, AgILgel exhibits significantly improved tensile properties, adhesion, and overall performance when compared to previously reported ionogels (Fig. 1 f) 43 – 52 . Mechanical and Adhesion Properties of the AgILgel The polymer content in ionogels plays a crucial role in maintaining their mechanical properties. To investigate this, we studied the effect of varying AA content on the stress-strain behavior and softness of the ionogel. The results indicated that as the AA content decreased, both the stress and Young's modulus of the ionogel decreased significantly, while the strain increased (Fig. 2 a and 2 b). This suggests that the reduction in polymer content leads to a less densely crosslinked network, resulting in greater flexibility and softness, which allows for enhanced deformability under applied forces. As a result, the AgILgel becomes more adaptable to external forces, reflecting its improved deformability and increased softness. We further examined the influence of AgNWs incorporation on the mechanical properties of the AgILgel. As shown in Fig S2 , no significant changes in the stress-strain behavior were observed with increasing AgNWs content. This is because the AgNWs are uniformly integrated into the network without disrupting its structural integrity. Comparison between the mechanical properties of AgILgel and ionogel showed no significant changes in maximum stress, strain or Young's modulus (Fig. 2 c). This indicates that the addition of AgNWs does not significantly alter the mechanical properties of the ionogel but rather enhances its electrical conductivity without compromising its flexibility. The storage modulus (G′) and loss modulus (G′′) are important parameters of the ionogel’s mechanical behavior, where G′ reflects the material’s elasticity, and G′′ reflects its viscous behavior. As shown in Fig. 2 d, the storage modulus of AgILgel significantly exceeds the loss modulus, indicating its capacity to recover elastically after deformation. This feature enhances the AgILgel’s sensitivity to external stimuli and contributes to its superior performance in dynamic environments. Stability tests over 30 min. confirmed that the storage modulus remained consistently higher than the loss modulus, indicating AgILgel’s ability to maintain its elasticity over time (Fig. S3). Additionally, deformation resistance tests demonstrated that AgILgel retained its original shape after bending, twisting, and compressing (Fig. 2 e). Adhesion properties of AgILgel were evaluated using lap-shear tests 53 , which measure its resistance to shear forces under applied stress (Fig. 2 f). The adhesion strengths of AgILgel to various substrates, including fish skin, frog skin, pig skin, and glass, were measured and found to be 84.60 kPa, 79.90 kPa, 46.44 kPa, and 28.48 kPa, respectively (Fig. 2 g, 2 h and S4). These results demonstrate that AgILgel exhibits strong adhesion to both biological and non-biological surfaces, making it suitable for self-adhesive electronic applications. Electrical Properties and Environmental Stability of AgILgel Electrical conductivity is a critical property for ionogel-based strain sensors 54 . We investigated the influence of AA and AgNWs content on the electrical conductivity of AgILgel. As shown in Fig. 3 a, conductivity increased with decreasing AA content, with a conductivity of 0.56 S/m observed at an AA content of 30%. The addition of AgNWs further enhanced the conductivity, which is attributed to the formation of an additional conductive pathway via the interconnected AgNWs. The sensitivity of the strain sensor was quantified using the gauge factor (GF), which is the ratio of the relative change in resistance to applied strain. Below 50% strain, the GF of AgILgel was 0.58, and it increased to 1.24 when the strain ranged from 50–300% (Fig. 3 b). Fatigue resistance and repeatability tests showed that AgILgel exhibited excellent stability, with minimal variation in resistance after 60 cycles of loading-unloading at 50% strain (Fig. 3 c). The response time of AgILgel was calculated to be 800 ms, ensuring prompt detection of strain changes. Moreover, when attached to a finger joint to monitor bending motions, AgILgel responded promptly to joint movements, further demonstrating its reliability as a strain sensor (Fig. 3 d). The change in resistance (ΔR/R₀) was investigated over five dynamic strain cycles within a strain range of 100–400% (Fig. 3 e). The results demonstrate that the peak ΔR/R₀ exhibits a direct proportionality to the applied strain. The symmetric response indicates that the resistance recovery rate is comparable to the strain loading rate, thereby confirming the structural stability of the strain sensor. Environmental stability is essential for the long-term performance of flexible sensors. To evaluate the thermal stability of AgILgel, we subjected it to a heating test at 80°C for 1 hour. AgILgel maintained its structural integrity and functional properties, whereas the mass of SA hydrogel decreased by approximately 90% due to water loss (Fig. 3 f and 3 g). The significant loss of water in the hydrogel resulted in a decline in conductivity and a deterioration of tensile properties, whereas AgILgel preserved both its electrical and mechanical characteristics following the same heat treatment (Fig. 3 h, S5, and S6). AgILgel also demonstrated self-healing properties, maintaining electrical conductivity even after being severed and subsequently rejoined (Fig. S7). Furthermore, the incorporation of silver nanowires endows AgILgel with outstanding antibacterial properties, exhibiting an inhibition zone diameter of 16.7 mm against MRSA and 17.4 mm against E. coli (Fig. S8). AgILgel for Bio-Wireless Health Monitoring The movement patterns of aquatic animals can provide valuable insights into their health status. Monitoring these movements is critical for scientific research and environmental protection. However, due to the soft and variable body shapes of many aquatic animals, wearable sensors designed for their monitoring must exhibit exceptional stretchability and flexibility. AgILgel meets these requirements, offering a highly sensitive and reliable strain sensor for real-time monitoring of aquatic animal movements. We integrated AgILgel into a wireless monitoring system, as shown in Fig. 4 a, to monitor the movements of aquatic animals like the sturgeon. The wireless sensor, attached to the sturgeon’s gills or tail, collected data on the animal’s movement, which was wirelessly transmitted via Bluetooth to a mobile application for further analysis (Fig. 4 b-c). The sensor successfully detected small deformation changes (down to 0.5%), indicating its high sensitivity for monitoring subtle movement patterns (Fig. 4 d). The system was also used to monitor the gill movements of the sturgeon, reflecting its respiratory state (Fig. 4 e-f). The AgILgel was then affixed to the muscle connecting the gills to the body of the sturgeon to monitor gill movement, thereby providing insights into the respiratory activity of the sturgeon (Fig. 4 e). AgILgel was highly sensitive in detecting subtle variations in gill movement. During large gill movements, the gill slit gape widened, resulting in a strong signal transmitted by the AgILgel-based Bluetooth sensor. Conversely, when gill movements were minimal, the gape narrowed, and the transmitted signal weakened (Fig. 4 f ). To evaluate changes in the respiratory state of the Chinese sturgeon before and after stimulation, AgILgel was affixed to the gills to monitor breathing patterns prior to stimulus application. Eugenol methyl ether, a local anesthetic with effects on both the nervous and muscular systems, was used as the stimulus (Fig. 4 g). As shown in Fig. 4 h, prior to stimulation, the Chinese sturgeon exhibited a regular and stable breathing pattern, indicating a healthy state. After stimulation, the fish displayed erratic body movements, disrupted breathing, and fluctuating data signals, which gradually weakened. This suggests that the AgILgel-based wearable electronic is effective for monitoring the respiratory behavior of aquatic animals, such as the Chinese sturgeon, providing real-time physiological data. In addition to monitoring gill movement in sturgeon, AgILgel was also affixed to the tail to assess tail-beat motion (Fig. S9). Furthermore, AgILgel was employed to monitor movement in amphibians, with tests conducted on the common bullfrog. The vocal sac of the male bullfrog is a specialized structure involved in reproductive behavior. During the breeding season, male bullfrogs produce calls to attract females, and the vocal sac serves both as a resonator during calling and as a component in respiration. Normal movement of the vocal sac indicates normal reproductive behavior, while abnormal movement may suggest respiratory dysfunction. AgILgel was attached to the bullfrog’s vocal sac and connected to a Bluetooth transmission device to monitor its motion. The obtained data exhibited a clear pattern, reflecting the bullfrog's health status (Fig. S10). We applied AgILgel to monitor the vocal sac movements of a bullfrog and the jumping motion of its hind legs (Fig. S11), further confirming the versatility of AgILgel for biological monitoring applications. Conclusion In conclusion, AgILgel presents a promising material for bioelectronics and sensor applications, combining high electrical conductivity, excellent mechanical properties, and strong adhesion to biological substrates. Its ability to conform to dynamic, soft, and irregular surfaces makes it an ideal candidate for use in wearable and implantable sensors, particularly for monitoring the movements of aquatic animals and amphibians. The successful integration of AgILgel with wireless transmission technology further enhances its practical applicability, enabling real-time health monitoring of biological systems. The material’s self-healing capabilities and excellent environmental stability make it a robust and sustainable choice for long-term applications in diverse and challenging environments. Future work will focus on optimizing the material's performance for even more specialized applications, including environmental monitoring, biomedical diagnostics, and soft robotics. Declarations Supporting Information Supporting Information is available from the website or from the author. Acknowledgments This work was supported by the National Natural Science Foundation of China (22176221), and the Central Public-interest Scientific Institution Basal Research Fund (CAFS: 2024XT09). Author contributions L. W. guided the entire work. Y. 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Soft, Stretchable, and Conductive Hydrogel Based on Liquid Metal for Accurately Facial Expression Monitoring [J]. Advanced Materials Technologies, 2023, 8(17): 1-10. Additional Declarations No competing interests reported. Supplementary Files supplementinformation.docx supplementVideo.mp4 Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5757703","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":401928214,"identity":"18342ab8-e230-432a-a10b-01f777bfcc3b","order_by":0,"name":"Yahui Wen","email":"","orcid":"","institution":"Shanghai Ocean University","correspondingAuthor":false,"prefix":"","firstName":"Yahui","middleName":"","lastName":"Wen","suffix":""},{"id":401928215,"identity":"8ee6a92b-b8a1-4739-b94f-e5975f280f8e","order_by":1,"name":"Xinghai Wang","email":"","orcid":"","institution":"Shanghai Ocean University","correspondingAuthor":false,"prefix":"","firstName":"Xinghai","middleName":"","lastName":"Wang","suffix":""},{"id":401928216,"identity":"50a74b3c-4ee6-47e5-8a8b-dd28174cf4fd","order_by":2,"name":"Jinxue Zhao","email":"","orcid":"","institution":"Shanghai Ocean University","correspondingAuthor":false,"prefix":"","firstName":"Jinxue","middleName":"","lastName":"Zhao","suffix":""},{"id":401928217,"identity":"54b0b6e0-95d6-4628-991a-e030b948f485","order_by":3,"name":"Xuejing Zhai","email":"","orcid":"","institution":"Chinese Academy of Fishery Sciences","correspondingAuthor":false,"prefix":"","firstName":"Xuejing","middleName":"","lastName":"Zhai","suffix":""},{"id":401928218,"identity":"9775b705-926c-4413-ae6e-1b64bf2054fd","order_by":4,"name":"Wei Xia","email":"","orcid":"","institution":"Chinese Academy of Fishery Sciences","correspondingAuthor":false,"prefix":"","firstName":"Wei","middleName":"","lastName":"Xia","suffix":""},{"id":401928219,"identity":"eed96bbd-01cc-456d-9a1f-90b13e15eaa1","order_by":5,"name":"Peiyi Li","email":"","orcid":"","institution":"Chinese Academy of Fishery Sciences","correspondingAuthor":false,"prefix":"","firstName":"Peiyi","middleName":"","lastName":"Li","suffix":""},{"id":401928220,"identity":"a29e88c3-fbf0-4ecd-9046-351a45536199","order_by":6,"name":"Keqiang Lai","email":"","orcid":"","institution":"Shanghai Ocean University","correspondingAuthor":false,"prefix":"","firstName":"Keqiang","middleName":"","lastName":"Lai","suffix":""},{"id":401928221,"identity":"9d5cf349-7aac-4f5d-bdab-41b2443d2321","order_by":7,"name":"Meiwen Zhu","email":"","orcid":"","institution":"Chongqing Academy of Metrology and Quality Inspection","correspondingAuthor":false,"prefix":"","firstName":"Meiwen","middleName":"","lastName":"Zhu","suffix":""},{"id":401928224,"identity":"89b17f57-39cc-4cb2-9d10-6bf396c47282","order_by":8,"name":"Zhengde Lin","email":"","orcid":"","institution":"Chinese Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"Zhengde","middleName":"","lastName":"Lin","suffix":""},{"id":401928227,"identity":"894a171e-e58c-440a-b1ab-7462ee968039","order_by":9,"name":"Tuyan Luo","email":"","orcid":"","institution":"Fujian Academy of Agricultural Sciences","correspondingAuthor":false,"prefix":"","firstName":"Tuyan","middleName":"","lastName":"Luo","suffix":""},{"id":401928229,"identity":"45bfb08e-8f92-405a-96b7-44563fa30b94","order_by":10,"name":"Lidong Wu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAqElEQVRIiWNgGAWjYFAC5gaJDwwM/KRoYWyQnMHAINlAkhZpHpK0GNxIbLxtU2MnId/A/PADQ80dorQ0W+ccS5YwOMBmLMFw7BlhLWY3EtukcxuY6wyAbKAjDxOpxbKhHugw9m8kaAGqlGA4wEOkLfZnHjZb9hw7LmFwmKdYIuEYEVok25MP3vhRUy0h396+8cOHGiK0IAAzECeQomEUjIJRMApGAW4AAKaVNm+uK7HDAAAAAElFTkSuQmCC","orcid":"","institution":"Shanghai Ocean University","correspondingAuthor":true,"prefix":"","firstName":"Lidong","middleName":"","lastName":"Wu","suffix":""}],"badges":[],"createdAt":"2025-01-03 10:53:38","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5757703/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5757703/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":73863764,"identity":"483b8fdb-d4e4-43d5-82f2-819ecebc918a","added_by":"auto","created_at":"2025-01-15 11:24:43","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":310354,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Schematic illustration comparing the attachment of AgILgel ionogel and conventional rigid ionogels to the fish epidermis. (b) Magnified depiction of the interaction between AgILgel ionogel and the fish epidermis in comparison to rigid ionogels. (c) Fabrication process and cross-linked structure of AgILgel ionogel. (d) Conductive pathway in conventional ionogels. (e) Conductive pathway in AgILgel ionogel. (f) Comparison of the ionogel-based sensor developed in this study with similar works reported previously.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-5757703/v1/bab8244198c1e7ccc8562391.png"},{"id":73863946,"identity":"f1b12f3e-e23f-4bda-a5bc-4cfb02258821","added_by":"auto","created_at":"2025-01-15 11:32:43","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":311905,"visible":true,"origin":"","legend":"\u003cp\u003eMechanical and Adhesive Properties of AgILgel. (a) Effect of acrylic polymer content on the stress-strain behavior of ionogels. (b) Effect of acrylic polymer content on the Young’s modulus of ionogels. (c) Stress-strain curves and Young’s modulus comparison between 30% polymer content [EMIM] ionogel and AgILgel. (d) Storage modulus and loss modulus of AgILgel under different frequencies. (e) Compression and twisting deformation tests of AgILgel under applied pressure. (f) Schematic diagram of the lap shear adhesion test setup for ionogels. (g) Photographs of AgILgel adhered to fish muscle, frog muscle, fish skin, and frog skin. (h) Shear strength of AgILgel adhered to fish skin, frog skin, pig skin, and glass.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-5757703/v1/6052598bedc3425ac334c311.png"},{"id":73862786,"identity":"76381977-5123-40c0-aa5f-9df3ef80a1a0","added_by":"auto","created_at":"2025-01-15 11:16:43","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":308943,"visible":true,"origin":"","legend":"\u003cp\u003eElectrical Properties and Environmental Stability of AgILgel. (a) Effect of different acrylic polymer and silver nanowire contents on the conductivity of ionogels. (b) Relative resistance change of AgILgel under continuous tensile strain ranging from 0% to 300%. (c)\u003cstrong\u003e \u003c/strong\u003eResponse time and anti-fatigue performance testing of AgILgel. (d) Basic test of AgILgel for monitoring finger movements. (e) The relative resistance change (ΔR/R0) of LM/CNTs hydrogel under cyclic loading-unloading at high strains (100%, 200%, 300%, 400%). (f) Effect of heat treatment time on the morphology of SA hydrogel and AgILgel. (g) Effect of heat treatment time on the mass of SA hydrogel and AgILgel. (h) Comparison of the electrical properties of the two materials before and after heating.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-5757703/v1/bac836788c0ff5f84eeff78f.png"},{"id":73862787,"identity":"5b4386d7-31d7-4a91-b5a9-a927a14c3544","added_by":"auto","created_at":"2025-01-15 11:16:43","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":419386,"visible":true,"origin":"","legend":"\u003cp\u003eApplications of the Wireless Transmission Monitoring System. (a) Exploded diagram of the Bluetooth device. (b-c) Block diagram of the wireless transmission monitoring system. (d) Test of the strain sensor's lowest detection limit under different stretch levels (0.5%, 2.5%, and 5%). (e) Real-time monitoring of fish gill respiratory motion using the AgILgel-based wireless transmission monitoring system. (f) Photograph showing the range of fish gill movements. (g) Schematic diagram illustrating the application of external stimuli to sturgeon. (h) Changes in fish gill movement data before and after applying stimuli to the sturgeon.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-5757703/v1/a18c4957272db21ee4855ea8.png"},{"id":77374216,"identity":"36d4790d-dbb0-4dcd-9c9f-f12c55142318","added_by":"auto","created_at":"2025-02-28 01:53:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1902703,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5757703/v1/d9accc8c-3263-485a-b060-c41db8b5a7c8.pdf"},{"id":73862788,"identity":"1de18f78-29ea-4a5f-a6de-fbefb55c23a4","added_by":"auto","created_at":"2025-01-15 11:16:44","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":3130773,"visible":true,"origin":"","legend":"","description":"","filename":"supplementinformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-5757703/v1/765ca224f948a89640acde31.docx"},{"id":73862801,"identity":"7fba2661-4749-4c9c-a024-5515b5f5480e","added_by":"auto","created_at":"2025-01-15 11:16:45","extension":"mp4","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":43066083,"visible":true,"origin":"","legend":"","description":"","filename":"supplementVideo.mp4","url":"https://assets-eu.researchsquare.com/files/rs-5757703/v1/98b9c77471dbb942afeaf09b.mp4"}],"financialInterests":"No competing interests reported.","formattedTitle":"A High-Conductivity and Adhesive Ionogel Strain Sensor for Monitoring Stimulus-Response Behavior of Aquatic Organism","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe development of flexible\u003csup\u003e\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e, conductive materials for use in bio-sensing applications has become an area of intense interest due to their potential to monitor biological phenomena in real-time\u003csup\u003e\u003cspan additionalcitationids=\"CR6 CR7 CR8 CR9 CR10 CR11\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Sensors capable of detecting the movements of living organisms\u003csup\u003e\u003cspan additionalcitationids=\"CR14 CR15\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e, particularly soft-bodied animals, require materials that combine high electrical conductivity, mechanical flexibility, and strong adhesion to irregular surfaces\u003csup\u003e\u003cspan additionalcitationids=\"CR18 CR19\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. These sensors not only conform closely to the skin, reducing noise and artifacts caused by poor contact, but also collect high-quality data continuously without causing discomfort\u003csup\u003e\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. Currently, hydrogel-fabricated sensors are widely used for their superior conductivity and good mechanical stability\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. However, the hydrogel contains amount of water contents, which decreases the long-term performance due to its evaporation\u003csup\u003e\u003cspan additionalcitationids=\"CR27 CR28 CR29 CR30 CR31\" citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIonic liquids (ILs), which exhibit low volatility, high chemical stability, and excellent ionic conductivity, have emerged as promising materials for the fabrication of such sensors to overcome their evaporation\u003csup\u003e\u003cspan additionalcitationids=\"CR34\" citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. However, conventional ionogels made from ionic liquids and polymers are typically rigid and suffer from low ionic conductivity due to the restrictive crosslinking of polymer chains, limiting their practical applications in flexible sensing\u003csup\u003e\u003cspan additionalcitationids=\"CR37 CR38 CR39\" citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e. Furthermore, most existing ionogels still suffer from poor mechanical properties, low conductivity, and high rigidity, which prevent them from tightly adhering to the aquatic organisms and monitoring their movements.\u003c/p\u003e \u003cp\u003eTo overcome these limitations, we propose a novel ionogel, which integrates silver nanowires (AgNWs) into imidazole-based ionic liquids (IL) \u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. The incorporation of AgNWs facilitates the creation of a robust conductive network, ensuring rapid electron migration and improved sensor performance\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. This design leverages the dual conductive pathways of ionic and electronic conduction, resulting in significantly enhanced conductivity. It also exhibits high flexibility, low Young\u0026rsquo;s modulus, and outstanding strain tolerance, making it capable of conforming to soft and complex surfaces, such as the skin of aquatic animals. In addition to its superior electrical and mechanical properties, the AgIL ionogel demonstrates excellent environmental stability, maintaining its functionality over a broad temperature range. Furthermore, the sensor's wireless data transmission capability, coupled with its high sensitivity and stability, enables real-time monitoring of aquatic animals\u0026rsquo; physiological states. This is particularly useful in environmental monitoring, where the detection of subtle changes in animal behavior can serve as an indicator of environmental stressors, such as pollution or habitat degradation.\u003c/p\u003e"},{"header":"Experimental section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eMaterial\u003c/h2\u003e \u003cp\u003e1-Butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][OTf],97%) and acrylic acid (AA) purchased from Macklin (Shanghai, China). Sodium alginate (SA, 99%), acrylamide (AM, \u0026ge; 99%) N, N\u0026rsquo;- methylenebis(acrylamide) (BIS, 99%), ammonium persulfate (APS, \u0026ge; 98%), N, N, N\u0026rsquo;, N\u0026rsquo;-tetramethyl ethylenediamine (TEMED, 99%), and sodium chloride (NaCl, \u0026ge; 99%) purchased from Sigma Aldrich (Shanghai, China). 3-Ethyl-1-methylimidazolium trifluoromethanesulfonate ([EMIM][OTf], 98%) and silver nanowires (AgNWs, diameter: 60nm, length: 45 \u0026micro;m) purchased from Anpel (Shanghai, China).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003ePreparation of AgIL ionogel\u003c/h3\u003e\n\u003cp\u003eAs a representative example, AgIL ionogel was prepared by dissolving APS (4.5 mg) and BIS (4.5 mg) in [BMIM][OTf] (2.1 g) using ultrasonic treatment. AgNWs(0.12 g) was then added to the solution and sonicated using an ultrasonic homogenizer to achieve a homogeneous dispersion of AgNWs in the IL. AA (0.9g) was added to this mixture, followed by thoroughly shaking. The resulting solution was poured into a polytetrafluoroethylene (PTFE) mold and cured at 90\u0026deg;C for 8 hours to yield the final AgIL ionogel. For the preparation of a soft [BMIM] ionogel without AgNW, 30AA was synthesized by following the same method.\u003c/p\u003e \u003cp\u003eFor the preparation of a traditional rigid ionogel, APS and BIS were dissolved in [BMIM][OTf] by ultrasonic treatment.AA was then added, and the mixture was shaken thoroughly. The resulting solution was poured into a PTFE mold and heated at 85\u0026deg;C for 2 hours to yield the final [BMIM][OTf] ionic gel.\u003c/p\u003e \u003cp\u003eFor the preparation of the SA hydrogel, six solutions\u0026mdash;SA (2 mL, 4.8%), AAM (2.75 mL, 19%), APS (70 \u0026micro;L, 0.2 mol L⁻\u0026sup1;), BIS (600 \u0026micro;L, 2 wt.%), TEMED, and NaCl (300 \u0026micro;L, 1 mol L⁻\u0026sup1;) were mixed and cured under 365 nm UV light for 1 hour. BIS, APS, and TEMED acted as the crosslinker, photoinitiator, and crosslinking accelerator, respectively, to form the final SA hydrogel.\u003c/p\u003e\n\u003ch3\u003eMechanical test\u003c/h3\u003e\n\u003cp\u003eMechanical properties of the ionic gels were evaluated using a universal testing machine (ZQ990LB, Chitake, China). Tensile tests were conducted at ambient conditions (25℃, 40% relative humidity) with a 100 N load cell at a constant strain rate of 100 mm/min, unless otherwise stated. Tensile-release tests were carried out under the same conditions with rectangular specimens (30 mm in length, 10 mm in width, and 2 mm in thickness). Cyclic tensile tests were performed using a uniaxial stretching machine at a constant compression rate. All test were repeated at least three times with independent samples. Young's modulus was calculated from the average slope of the stress-strain curve in the strain range of 20\u0026ndash;60%.\u003c/p\u003e\n\u003ch3\u003eElectrical conductivity test\u003c/h3\u003e\n\u003cp\u003eThe resistance (R) of the materials was measured using LCR digital bridge tester (EA4980AL, Keysight) and the electrical conductivity (σ) was calculated as follows:\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\sigma\\:=\\frac{L}{R\\times\\:S}\\:\\)\u003c/span\u003e\u003c/span\u003e\u0026hellip;\u0026hellip;\u0026hellip; (1)\u003c/p\u003e \u003cp\u003eWhere (L) and (S) represent the gauge length and cross-sectional area of the ionic conductor, respectively. The samples were prepared with length of 25 mm, width of 10 mm, and thickness of 2 mm. The relative resistance was measured using an LCR meter. The relative resistance change (ΔR/R₀) of the stretched samples was calculated as follows:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:\\varDelta\\:R/{R}_{0}=\\frac{{R}_{t}-{R}_{0}}{{R}_{0}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u0026hellip;\u0026hellip;\u0026hellip;\u003c/p\u003e \u003cp\u003eWhere (R\u003csub\u003et\u003c/sub\u003e) and (R\u003csub\u003e0\u003c/sub\u003e) represent the relative resistance at the stretched and initial states, respectively. The gauge factor (GF) was defined as:\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:GF=\\left(\\frac{\\varDelta\\:R}{{R}_{0}}\\right)/\\epsilon\\:$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u0026hellip;\u0026hellip;\u0026hellip;\u003c/p\u003e \u003cp\u003eWhere (ε) is the applied strain.\u003c/p\u003e\n\u003ch3\u003eAdhesion tests\u003c/h3\u003e\n\u003cp\u003eLap-shear measurements were conducted using a general mechanical testing machine. The maximum stress force was divided by the corresponding contact area created by overlapping tissue samples to calculate the stress values. Rectangular slices of pig skin, fish skin, frog skin, and glass (15 mm \u0026times; 30 mm) were prepared. The AgIL ionogel was prepared in dimensions of 10 mm \u0026times; 10 mm \u0026times; 2 mm, with the overlapping area controlled at 10 mm \u0026times; 10 mm. The lap shear strength of the hydrogel was tested using a mechanical testing machine.\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cp\u003e \u003cb\u003eDesign and preparation of AgILgel.\u003c/b\u003e ILs are a class of fully ionized substances that remain in liquid form at room temperature. Owing to their rich C-F bonds, ILs exhibit low volatility, strong chemical and thermal stability, and hold promising potential for applications in fields such as wearable devices. However, ionogels fabricated from traditional ILs and polymers are typically hindered by a highly crosslinked polymer network, which restricts the mobility of ions within the gel matrix. This results in low conductivity and high rigidity, thereby preventing the gel from conforming to the dynamic movement of the skin. As demonstrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea and b, traditional rigid ionogel sensors fail to adapt to surfaces with varying shapes during monitoring, limiting their ability to deform in response to the real-time movements. Consequently, we have developed a flexible ionogel sensor designed for the continuous monitoring of aquatic animals movements, such as fish. This novel ionogel can closely conform to the surface of the soft skin and respond to its movement with corresponding shape alterations. Young's modulus, a measure of the material\u0026rsquo;s resistance to elastic deformation under stress, serves as an indicator of the ionogel\u0026rsquo;s softness. Lower Young's modulus values correlate with increased softness, resulting in enhanced adhesion to the soft skin.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAgNWs, known for their high electrical conductivity (354 S/cm) and antimicrobial ability, are employed as nanofillers to enhance the conductivity of the ionogel. AgNWs facilitate electron migration within the material, acting as conductive bridges and significantly improving the overall conductivity. The AgILgel was synthesized using a simple \u0026ldquo;one-pot\u0026rdquo; method, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec. The unique structure of ILs ensures the structural integrity of the homogeneously dispersed AgNWs (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e), while electrostatic and physical interlocking interactions between the ILs and AgNWs help preserve their electrical properties, further enhancing the conductivity of AgILgel.\u003c/p\u003e \u003cp\u003eIn addition to its softness, excellent conformability, and rapid deformation response, AgILgel demonstrates superior electrical conductivity compared to traditional ionogels. The conductivity of conventional ionogels depends on the migration of internal ions through these conductive pathways (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). Upon compression, ion gradients form due to the differential mobilities of anions and cations, generating a voltage signal. In contrast, AgILgel benefits from dual conductive pathways: conventional ionic conduction and electron conduction via AgNWs (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee), resulting in significantly enhanced electrical performance. Moreover, AgILgel exhibits significantly improved tensile properties, adhesion, and overall performance when compared to previously reported ionogels (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ef) \u003csup\u003e\u003cspan additionalcitationids=\"CR44 CR45 CR46 CR47 CR48 CR49 CR50 CR51\" citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003ch3\u003eMechanical and Adhesion Properties of the AgILgel\u003c/h3\u003e\n\u003cp\u003eThe polymer content in ionogels plays a crucial role in maintaining their mechanical properties. To investigate this, we studied the effect of varying AA content on the stress-strain behavior and softness of the ionogel. The results indicated that as the AA content decreased, both the stress and Young's modulus of the ionogel decreased significantly, while the strain increased (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). This suggests that the reduction in polymer content leads to a less densely crosslinked network, resulting in greater flexibility and softness, which allows for enhanced deformability under applied forces. As a result, the AgILgel becomes more adaptable to external forces, reflecting its improved deformability and increased softness.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWe further examined the influence of AgNWs incorporation on the mechanical properties of the AgILgel. As shown in Fig \u003cspan refid=\"MOESM2\" class=\"InternalRef\"\u003eS2\u003c/span\u003e, no significant changes in the stress-strain behavior were observed with increasing AgNWs content. This is because the AgNWs are uniformly integrated into the network without disrupting its structural integrity. Comparison between the mechanical properties of AgILgel and ionogel showed no significant changes in maximum stress, strain or Young's modulus (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec). This indicates that the addition of AgNWs does not significantly alter the mechanical properties of the ionogel but rather enhances its electrical conductivity without compromising its flexibility.\u003c/p\u003e \u003cp\u003eThe storage modulus (G\u0026prime;) and loss modulus (G\u0026prime;\u0026prime;) are important parameters of the ionogel\u0026rsquo;s mechanical behavior, where G\u0026prime; reflects the material\u0026rsquo;s elasticity, and G\u0026prime;\u0026prime; reflects its viscous behavior. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed, the storage modulus of AgILgel significantly exceeds the loss modulus, indicating its capacity to recover elastically after deformation. This feature enhances the AgILgel\u0026rsquo;s sensitivity to external stimuli and contributes to its superior performance in dynamic environments. Stability tests over 30 min. confirmed that the storage modulus remained consistently higher than the loss modulus, indicating AgILgel\u0026rsquo;s ability to maintain its elasticity over time (Fig. S3). Additionally, deformation resistance tests demonstrated that AgILgel retained its original shape after bending, twisting, and compressing (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee).\u003c/p\u003e \u003cp\u003eAdhesion properties of AgILgel were evaluated using lap-shear tests\u003csup\u003e\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e, which measure its resistance to shear forces under applied stress (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef). The adhesion strengths of AgILgel to various substrates, including fish skin, frog skin, pig skin, and glass, were measured and found to be 84.60 kPa, 79.90 kPa, 46.44 kPa, and 28.48 kPa, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eg, \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eh and S4). These results demonstrate that AgILgel exhibits strong adhesion to both biological and non-biological surfaces, making it suitable for self-adhesive electronic applications.\u003c/p\u003e\n\u003ch3\u003eElectrical Properties and Environmental Stability of AgILgel\u003c/h3\u003e\n\u003cp\u003eElectrical conductivity is a critical property for ionogel-based strain sensors\u003csup\u003e\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e\u003c/sup\u003e. We investigated the influence of AA and AgNWs content on the electrical conductivity of AgILgel. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea, conductivity increased with decreasing AA content, with a conductivity of 0.56 S/m observed at an AA content of 30%. The addition of AgNWs further enhanced the conductivity, which is attributed to the formation of an additional conductive pathway via the interconnected AgNWs. The sensitivity of the strain sensor was quantified using the gauge factor (GF), which is the ratio of the relative change in resistance to applied strain. Below 50% strain, the GF of AgILgel was 0.58, and it increased to 1.24 when the strain ranged from 50\u0026ndash;300% (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFatigue resistance and repeatability tests showed that AgILgel exhibited excellent stability, with minimal variation in resistance after 60 cycles of loading-unloading at 50% strain (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). The response time of AgILgel was calculated to be 800 ms, ensuring prompt detection of strain changes. Moreover, when attached to a finger joint to monitor bending motions, AgILgel responded promptly to joint movements, further demonstrating its reliability as a strain sensor (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed). The change in resistance (ΔR/R₀) was investigated over five dynamic strain cycles within a strain range of 100\u0026ndash;400% (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee). The results demonstrate that the peak ΔR/R₀ exhibits a direct proportionality to the applied strain. The symmetric response indicates that the resistance recovery rate is comparable to the strain loading rate, thereby confirming the structural stability of the strain sensor.\u003c/p\u003e \u003cp\u003eEnvironmental stability is essential for the long-term performance of flexible sensors. To evaluate the thermal stability of AgILgel, we subjected it to a heating test at 80\u0026deg;C for 1 hour. AgILgel maintained its structural integrity and functional properties, whereas the mass of SA hydrogel decreased by approximately 90% due to water loss (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eg). The significant loss of water in the hydrogel resulted in a decline in conductivity and a deterioration of tensile properties, whereas AgILgel preserved both its electrical and mechanical characteristics following the same heat treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eh, S5, and S6). AgILgel also demonstrated self-healing properties, maintaining electrical conductivity even after being severed and subsequently rejoined (Fig. S7). Furthermore, the incorporation of silver nanowires endows AgILgel with outstanding antibacterial properties, exhibiting an inhibition zone diameter of 16.7 mm against \u003cb\u003eMRSA\u003c/b\u003e and 17.4 mm against \u003cb\u003eE. coli\u003c/b\u003e (Fig. S8).\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eAgILgel for Bio-Wireless Health Monitoring\u003c/h2\u003e \u003cp\u003eThe movement patterns of aquatic animals can provide valuable insights into their health status. Monitoring these movements is critical for scientific research and environmental protection. However, due to the soft and variable body shapes of many aquatic animals, wearable sensors designed for their monitoring must exhibit exceptional stretchability and flexibility. AgILgel meets these requirements, offering a highly sensitive and reliable strain sensor for real-time monitoring of aquatic animal movements.\u003c/p\u003e \u003cp\u003eWe integrated AgILgel into a wireless monitoring system, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, to monitor the movements of aquatic animals like the sturgeon. The wireless sensor, attached to the sturgeon\u0026rsquo;s gills or tail, collected data on the animal\u0026rsquo;s movement, which was wirelessly transmitted via Bluetooth to a mobile application for further analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb-c). The sensor successfully detected small deformation changes (down to 0.5%), indicating its high sensitivity for monitoring subtle movement patterns (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed). The system was also used to monitor the gill movements of the sturgeon, reflecting its respiratory state (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee-f). The AgILgel was then affixed to the muscle connecting the gills to the body of the sturgeon to monitor gill movement, thereby providing insights into the respiratory activity of the sturgeon (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee). AgILgel was highly sensitive in detecting subtle variations in gill movement. During large gill movements, the gill slit gape widened, resulting in a strong signal transmitted by the AgILgel-based Bluetooth sensor. Conversely, when gill movements were minimal, the gape narrowed, and the transmitted signal weakened (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef ).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo evaluate changes in the respiratory state of the Chinese sturgeon before and after stimulation, AgILgel was affixed to the gills to monitor breathing patterns prior to stimulus application. Eugenol methyl ether, a local anesthetic with effects on both the nervous and muscular systems, was used as the stimulus (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eg). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eh, prior to stimulation, the Chinese sturgeon exhibited a regular and stable breathing pattern, indicating a healthy state. After stimulation, the fish displayed erratic body movements, disrupted breathing, and fluctuating data signals, which gradually weakened. This suggests that the AgILgel-based wearable electronic is effective for monitoring the respiratory behavior of aquatic animals, such as the Chinese sturgeon, providing real-time physiological data.\u003c/p\u003e \u003cp\u003eIn addition to monitoring gill movement in sturgeon, AgILgel was also affixed to the tail to assess tail-beat motion (Fig. S9). Furthermore, AgILgel was employed to monitor movement in amphibians, with tests conducted on the common bullfrog. The vocal sac of the male bullfrog is a specialized structure involved in reproductive behavior. During the breeding season, male bullfrogs produce calls to attract females, and the vocal sac serves both as a resonator during calling and as a component in respiration. Normal movement of the vocal sac indicates normal reproductive behavior, while abnormal movement may suggest respiratory dysfunction. AgILgel was attached to the bullfrog\u0026rsquo;s vocal sac and connected to a Bluetooth transmission device to monitor its motion. The obtained data exhibited a clear pattern, reflecting the bullfrog's health status (Fig. S10). We applied AgILgel to monitor the vocal sac movements of a bullfrog and the jumping motion of its hind legs (Fig. S11), further confirming the versatility of AgILgel for biological monitoring applications.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn conclusion, AgILgel presents a promising material for bioelectronics and sensor applications, combining high electrical conductivity, excellent mechanical properties, and strong adhesion to biological substrates. Its ability to conform to dynamic, soft, and irregular surfaces makes it an ideal candidate for use in wearable and implantable sensors, particularly for monitoring the movements of aquatic animals and amphibians. The successful integration of AgILgel with wireless transmission technology further enhances its practical applicability, enabling real-time health monitoring of biological systems. The material\u0026rsquo;s self-healing capabilities and excellent environmental stability make it a robust and sustainable choice for long-term applications in diverse and challenging environments. Future work will focus on optimizing the material's performance for even more specialized applications, including environmental monitoring, biomedical diagnostics, and soft robotics.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eSupporting Information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSupporting Information is available from the website or from the author.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the National Natural Science Foundation of China (22176221), and the Central Public-interest Scientific Institution Basal Research Fund (CAFS: 2024XT09).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eL. W. guided the entire work.\u0026nbsp;Y. W. designed and performed the experiments and processed the data and interpreted the data and edited the manuscript. X.W., J.Z. and X.Z. participated in the design of figures. K.L., M.Z., Z.L., T.L., W.X. and P.L. revised the first draft. All authors have approved the final version of the manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eZHENG L, et al. Conductance-stable liquid metal sheath-core microfibers for stretchy smart fabrics and self-powered sensing [J]. Sci Adv, 2021, 7(22): 1-10.\u003c/li\u003e\n\u003cli\u003eLING Y, et al. Disruptive, Soft, Wearable Sensors [J]. Adv Mater, 2020, 32(18): 1-10.\u003c/li\u003e\n\u003cli\u003eLEE Y W, et al. Multifunctional 3D-Printed Pollen Grain-Inspired Hydrogel Microrobots for On-Demand Anchoring and Cargo Delivery [J]. Adv Mater, 2023, 35(10): 1-10.\u003c/li\u003e\n\u003cli\u003eCHEN S, et al. 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Advanced Materials Technologies, 2023, 8(17): 1-10.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Wearable electronics, silver nanowires, ionogel, high electrical conductivity aquatic organisms, stimulus-response behavior","lastPublishedDoi":"10.21203/rs.3.rs-5757703/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5757703/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIonogels have emerged as versatile materials with potential applications in flexible electronics and soft robotics. However, preparing high-performance ionogels with high conductivity and good mechanical strength remains challenging. Here, we report the development of a novel supramolecular ionogel as a wearable device for monitoring the stimulus-response behavior of aquatic animals. The integration of silver nanowires (AgNWs) endows the ionogel with good electrical conductivity (0.56 S m\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and mechanical robustness (strain tolerance \u0026rsaquo; 1400%). The ionic liquid (IL) makes the AgIL ionogel exhibit superior adhesion properties (84.6 kPa) across diverse substrates, including biological tissues (e.g., pig skin). Furthermore, this wearable electronic exhibit an ultra-low detection limit (0.5%). The wearable electronics device consists of flexible AgIL ionogels as the sensing material, a microcontroller, a signal processing circuit, and a Bluetooth transceiver. Its electrical responsiveness and stable cyclic performance highlight its potential for wearable applications. This device can clearly and continuously monitor the regular or various stimuli-induced movements of the gills, tail, and body of aquatic animals such as the Chinese sturgeon and bullfrog. Comparative studies with traditional rigid ionogels and hydrogels underscore the significant enhancements in flexibility, adhesion, and conductivity by our design. This work provides a pathway for engineering multifunctional gels tailored for next generation soft electronic interfaces and broadens strain sensors' application range.\u003c/p\u003e","manuscriptTitle":"A High-Conductivity and Adhesive Ionogel Strain Sensor for Monitoring Stimulus-Response Behavior of Aquatic Organism","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-01-15 11:16:39","doi":"10.21203/rs.3.rs-5757703/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"010fe48f-0e42-4743-a74b-cc2d4b5d1261","owner":[],"postedDate":"January 15th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-02-28T01:53:11+00:00","versionOfRecord":[],"versionCreatedAt":"2025-01-15 11:16:39","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5757703","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5757703","identity":"rs-5757703","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}