Optically-induced electrical nano-patterning

Optically-induced electrical nano-patterning | 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 Research Article Optically-induced electrical nano-patterning Hyungmok Joh, Bin Lian, Nolan Cummins, Jiazheng Bao, Jang-Hwan Han, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8767694/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 Micro- and nanopatterning techniques are essential for fabricating next-generation devices in electronics, photonics, and biotechnology, as they dictate material properties, surface interactions, and device performance through precise structural control at critical scales. These methods underlie the development of multiple innovations, such as high-density sensors, lab-on-a-chip systems, and advanced screening platforms used in molecular biology. However, current patterning methods often face limitations in scalability, cost, and compatibility with sensitive materials. Here, we demonstrate an optically-induced electrical nano-painting technique that enables pattern formation over centimeter-scale areas with ~ 280 nm spatial precision. Operating at light intensities comparable to sunlight, this scalable method is compatible with a broad range of functional inks including live bacterial cells, inorganic nanoparticles, biomolecules, and ionic compounds. Materials Engineering nano-patterning large-scale printing 2D printing semi-3D printing Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction Patterning of materials is a widely employed technology that is essential in many diverse fields ranging from communication to device fabrication. Common to almost all applications, is the need to attain high resolution, fast printing speeds and ideally an ability to organize and position a wide range of materials. The latter is for instance essential when realizing biomedical sensing and array technologies. In comparison with serial processing, parallel methods are especially promising, when large area patterning is of importance. Considerable effort has been invested to address the need for high resolution using top-down lithography-based approaches, including photolithography, electron-beam lithography, and nanoimprint lithography. These techniques provide excellent pattern fidelity and precision, which have been widely combined with standard deposition and lift-off processes, surface functionalization, or templated trapping for placing nanoparticles and molecules. However, they typically require sophisticated instrumentation, multiple processing steps, cleanroom infrastructure, and material-specific chemicals, and in the case of electron beam lithography, advanced technical skills. A major limitation is that they require specific polymeric resists. For instance, it is impossible to print live or biological materials with these techniques. Beyond conventional lithography, 1–3 a variety of advanced strategies have been explored. Atomic Force Microscopy (AFM) enabled techniques, such as dip-pen nanolithography and related scanning probe methods, allow nanometer-scale placement of molecules and nanoparticles with exceptional precision, but due to their mostly serial nature are difficult to scale to larger print sizes. 4–6 Photochemical and photoactivated approaches employ light to locally trigger chemical reactions, binding, or crosslinking, enabling maskless patterning. While highly attractive due to their scalability, these methods are often restricted by specific photochemistries, limited ink diversity, and trade-offs between resolution and throughput. Given the constraints, there is a need for a parallel patterning method that affords high spatial resolution and broad material compatibility. In this work, we introduce a novel optically-induced electrical nano-printing method that enables patterning of a diverse range of materials over centimeter-scales with a spatial resolution of ~ 280 nm. The method relies on light-induced electrical activation of a surface, which in turn triggers the deposition of a broad range of functional inks. Modest light intensities are used to activate the substrate onto which inorganic nanoparticles (metals, polymers, and 2D materials), biomolecules (DNA, proteins, and cancer biomarkers), and even living bacterial cells can then be deposited. The particle size spans six orders of magnitude, from micrometers for bacteria down to a few nanometers for proteins. Even photorealistic nanopaintings can be achieved by the method which relies on the application of kilohertz (kHz)-range AC electric fields to a photosensitive amorphous silicon (a-Si) surface within an electrochemical cell (Fig. 1 ). The target ink or material, dispersed in an aqueous ionic support electrolyte (e.g., sodium sulfate), is then effectively deposited in the shape of the projected light images. The light-activation utilizes a digital light projector (DLP). Depending on the functionalization of the of the a-Si, the surface charge can be controlled. When functionalized with polyelectrolyte layers, PDDA yields positively charged surfaces, while PDDA/PSS produces negatively charged interfaces. 8 , 9 Surprisingly, only ink constituents carrying the same charge polarity are selectively deposited in light-defined regions. Alternately, it is also possible to use the method for light-directed removal (etching) of deposited materials. The combined deposition and etching yields feature sizes down to 278 nm using a standard microscope objective. Distinct from prior approaches, the reported technique can readily be used to form centimeter-scale patterns with sub-micrometer precision, for a very broad range of materials. The technique does not require physical masks, specialized biochemicals, ultraviolet illumination, or vacuum processing—constraints that commonly limit existing nanopatterning methods ( Table S1 ). 2. Working Mechanism, Characterization, and Optimization To understand the working mechanism, we systematically examine and characterize the effects of key components in the system (Fig. 2 ): (1) The a-Si layer, where the conductivity changes with the light pattern and selectively allows the light-controlled application of electric fields; (2) the polyelectrolyte layer, where charges are primarily stored and particles are deposited as a result of the E -field; (3) the solution, where the conductivity is determined by the salt concentration; and (4) the applied electric field itself, which governs the efficiency of particle deposition. As will be discussed below, the observed phenomena result not from a single component but from the combined effects of the entire system. Upon E -field application during light illumination, particles inside the solution gradually deposit onto the surface. Here, we use the density of the deposited particles (DDP) as a measure for the amount deposited, which critically depends on the amount of charge accumulated in and near the polyelectrolyte layer that enable the assembly. 2.1. The a-Si layer The DDP increases linearly as a function of the applied light intensity ( E -field: 12 Vpp, 1.5 kHz, 200 ms, waiting time after E -field application: 30 min+), as is seen in Fig. 2 A. This agrees with the dependence of the photocurrent ( i p ) on the photon rate ( N 0 ) 10 : $$\:{i}_{p}=e{N}_{0}\left(1-R\right)\left[1-\text{exp}\left(-\alpha\:d\right)\right]\text{ητ/}{t}_{t}$$ where R , α , d , η , τ , and t t are the surface reflection, surface absorption coefficient and depth, electron-hole pair generation efficiency, recombination lifetime, and carrier transit time, respectively. Negatively-charged 200nm polystyrene nanospheres can be assembled as a monolayer on a PDDA/PSS functionalized a-Si surface with a saturation DPP of ~ 3.5 particles/µm 2 (at ~ 650 mW/cm 2 ). At the lower intensity of 250 mW/cm 2 we obtain a DDP of ~ 1 particle/µm 2 , which indicates that it is possible to tune the density (gray scale) during printing. In the subsequent discussion we employ an intensity of 790 mW/cm 2 , unless indicated otherwise. 2.2. The polyelectrolyte layer The saturation DDP value increases with the number of polyelectrolyte bi-layers made of PDDA/PSS, with ~ 3.5, 9, and 14 particles /µm 2 corresponding to single, double, and triple layers, respectively (Fig. 2 B). We note that after applying an E -field burst (E-field: 12 Vpp, 1.5 kHz, 200 ms, and a light intensity of 790 mW/cm 2 ), the DDP gradually increases with time and plateaus at ~ 30min for all conditions. Interestingly, when we change the outermost functionalization layer to PDDA, 11 a positively charged polyelectrolyte, only positively-charged particles can be deposited onto the areas that are illuminated ( Fig. S1 ). Similarly, negatively-charged particles deposit on PSS-terminated surfaces (Fig. 2 H). Surprisingly, oppositely charged particles in suspension are not attracted to the surface. For instance, negatively-charged particles are repelled from the light-illuminated PDDA-terminated surfaces, as shown in the darkened area in Fig. S2 . The strong dependance of DDP on both the relative charge polarity of particle-surface pair and waiting time indicates that the working mechanism is based on electrostatics. The light-triggered polyelectrolyte-functionalized a-Si surface reverses its charge polarity. To determine if the working mechanism is only limited to a-Si surfaces, we also perform the same study on metal surfaces, such as Cu foam films ( Fig. S3 ). The results clearly indicate the same particle assembly effect as that observed on a-Si, further illustrating the generalizability of the working principle underlying the phenomena. 2.3. The applied E-field To unravel the role of the applied E -field, we systematically sweep the Vpp, frequency, and the total voltage application time. DDP linearly increases with Vpp and reaches its saturation at ~ 10 Vpp (1.5 kHz, 200ms, light intensity: 790 mW/cm 2 , waiting time: 30min). No obvious deposition is observed for Vpp values lower than 6 Vpp (Fig. 2 C). Similarly, DDP monotonically increases with the total time of the applied E -field (1.5 kHz, 12Vpp, light intensity: 790 mW/cm 2 , waiting time: 30min). Particle deposition starts at only 2 ms (Fig. 2 D, inset ) and saturates at 1000–2000 ms (Fig. 2 D). The experimental parameters of Vpp, E -field time, and light intensity positively correlate with the charge passing through the electrochemical cell up to a saturation point. This supports that the nature of the particle deposition is enabled by charges and electrostatics. While the DDP decreases with increasing frequency (Fig. 2 E), at frequencies higher than ~ 10 kHz particles no longer deposit on the substrate. The results agree with frequency-dependent response of ions in solution, in which ionic transport becomes increasingly ineffective as the applied AC field frequency increases. 12 2.4. The electrolyte Last, we probe the effect of the electrolyte, specifically the concentration of sodium sulfate ranging from a low 2.5 mM to a high 0.75 M, and its impact on the DDP. As long as particles are stably dispersed, 13 their assembly can be obtained reproducibly spanning all concentrations; the higher the concentration the greater the density. Not only simple electrolytes facilitate the deposition, but also more complex solutions relevant for biological samples, such as phosphate-buffered saline (PBS) also support assembly. This is notably different from previous works on dielectrophoresis (DEP)-enabled assembly, where particle manipulation and assembly mostly benefit from low ionic concentration, and where the effective electric fields applied to particles are greatly reduced in high ionic strengths. To further clarify that the present mechanism differs from DEP-enabled assembly, we examine the particles’ response in deionized water using the same setup and conditions. Particles are seen to primarily aggregate at the edges of the light patterns where the electric-field density and importantly the electric field gradient is the highest and not in the center of the patterns (which is clearly shown when the electrolyte is present) ( Fig. S4 ). 14 Both our theoretical understanding and experimental results thus indicate that the present method is not based on dielectrophoresis (DEP). Rather, the increase of particle density with ionic concentration suggests that the light-triggered electric charge accumulation and the electrochemical nature of the system drives the pattern process. In an electrochemical cell, the Debye screening length of the electric double layer reduces rapidly with ionic concentration. 15 Higher salt concentration also increases the electrolyte conductivity, causing a larger fraction of the voltage drop at the electric double layer and polyelectrolyte coating, resulting in increased ion transport speed. 16 The above extensive experimental study clearly reveals the counter charge accumulation in areas of electrolyte layers under light-activation in an AC field. The charge amount increases with the number polyelectrolyte-layer repeats, E -field time and strength, ionic concentration, and a reduction in the AC-frequency. 3. Versatile Nanopainting 3.1. 2D positive/negative patterning and particle reconfiguration We show that the method can be used to create images. As shown in Fig. 2 G, we paint a rose using 200-nm polystyrene nanoparticles. Here we notice that when applying multiple E -field bursts, a linear DDP increase is observed until 10 bursts, where a plateau is reached, agreeing with the results in Fig. 2 D. However, with 30 + bursts, the assembled particles gradually start to desorb from the surface with the number of subsequent E -field bursts (Fig. 2 H, Supporting notes ), showcasing the technique’s ability to not only deposit but also etch patterns. Therefore, we also successfully create negative images of the same rose by first depositing a uniform background followed by light-controlled etching (Fig. 2 I). Here, for double and triple PDDA/PSS bi-layers, the nanoparticles maintain their adhesion even after 50 + bursts, likely due to their increased adhesion to the a-Si surface. It should be noted that by applying an additional polyelectrolyte layer after etching, it becomes possible to redeposited particles at light-directed regions, paving the way for reconfigurable patterning (Fig. 2 J to L ). Last but not least, the technique is not restricted to single-layer 2D painting. By simply adding additional PDDA/PSS bi-layers on the nanopatterns, we readily create the second and third layers of patterns ( Fig. S5 ), which allows for 2.5-3D assembly. Resolution and optimization As is the case of any printing technology, patterning resolution is a key characteristic that determines the clarity and precision of the final output. 20 Here, we determine the resolution by printing an array of line patterns of varying widths and lengths (Fig. 3 A). We note that a change of the E -field frequency also slightly affects the output pattern size. When printing a square pattern with a fixed length value from the DLP device (= target length), the resulting output shows a linear decrease in the pattern’s length with increased frequency (Fig. 3 B). We find that 3 kHz generates a close match to the intended target length, which we therefore use for the resolution characterization below. For an ideal system, we can expect a 1:1 correspondence of DLP input pixel and the length of the deposited particles, meaning a y-axis intercept of 0 and a slope that would match the DLP-limited resolution. Experimentally, we obtain an intercept of 0.11, corresponding to ~ 110 nm, and a slope of 0.56, corresponding to ~ 560 nm, the resolution of the technique, agreeing with that of DLP minimum pixel size (Fig. 3 C). This resolution can be further improved by using an improved DLP system (more mirrors, increasing the resolution) and higher laser power (adequate light even at the smallest pixel sizes). When combining both deposition and etching, we create line patterns with a precision of 278 nm ( Fig. S6 ), effectively matching the Abbe criterion expected for a 532 nm light source (= 266 nm). This corresponds to a patterning resolution that exceeds 90,000 dots per inch. 3.2. Multiplex assembly The technique is highly versatile and is compatible with diverse inks. For demonstration, we deposit µm long B. Subtilis bacterial cells (Fig. 4 A) as well as nm-scale Au particles (Fig. 4 B), and complex Ag/SiO 2 nanoparticle composites ( Fig. S7 ), Ag nanowires (Fig. 4 C) and graphene oxide nanosheets (Fig. 4 D and E ). We also show that even salt (Na 2 SO 4 ) dissolved in solution (Fig. 4 F) can precipitate owing to the locally enhanced ion concentration. While the bacterial cells are directly observable via SEM, Au nanoparticles, graphene oxide nanosheets, are verified by using dark-field and Raman spectroscopy (Fig. 4 E), respectively. In particular, graphene oxide patterning is confirmed by the D and G bands in the Raman scattering 21 , 22 and Na 2 SO 4 is confirmed by EDX measurements (Fig. 4 F, inset ). It is also possible to pattern DNA (Fig. 4 G) and proteins (Fig. 4 H and I ), showing potential high-throughput analysis of molecular interactions, gene expression, and biomarker detection in biomedical assays and diagnostics. As a proof-of-concept, we demonstrate the co-deposition of P53, IL-6 antibody proteins onto a single chip ( Fig. S8 ), as well as dense arrays protein arrays made of IL-6 antibodies ( Fig. S9 ). 3.3. Large-scale particle deposition Finally, we evaluate the scalability of the deposition method. We demonstrate centimeter-scale particle patterning with a feature size of < 10 µm. The large-scale pattern is made using a single pattern as a “stamp”, while moving the stage and applying an E-field burst at each step. Alternatively, the electric field can be applied continuously, while patterns are created only in areas under light exposure, comparable to direct inkjet printing. For the former, we demonstrate a “Bevo” pattern, 1 cm x 0.5 cm wide (Fig. 5 A), made of numerous “Bevo” stamps (Fig. 5 B). Conclusions In this work, we report a novel, simple solution-based approach for particle deposition, based on charged polyelectrolyte layers and AC electric fields. The deposition area is activated by visible light, where the light pattern is formed using a projector paired with a photoconductive silicon surface. The quantity of particles deposited can be precisely controlled by changing the electric field, light intensity, and salt concentration. We show that a variety of functional and practical materials can be deposited, from cells to metallic nanoparticles and nanowires, DNA and proteins, and even salt. Finally, we demonstrate that the technique is highly scalable allowing cm-scale particle patterning. We anticipate that this technology will be used in a wide range of applications. References Gallatin GM, Liddle JA (2024) Photolithography: capabilities and limitations Harriott LR (2001) Limits of lithography. Proceedings of the IEEE 89, 366–374 Hoeneisen B, Mead CA (1972) Fundamental limitations in microelectronics—I. MOS technology. Solid State Electron 15:819–829 Muldoon K, Song Y, Ahmad Z, Chen X, Chang M-W (2022) High Precision 3D Printing for Micro to Nano Scale Biomedical and Electronic Devices. Micromachines (Basel) 13:642 Bhagoria P, Mathew Sebastian E, Kumar Jain S, Purohit J, Purohit R (2020) Nanolithography and its alternate techniques. Mater. 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Electrochim Acta 47:741–745 Palakkal VM et al (2020) Advancing electrodeionization with conductive ionomer binders that immobilize ion-exchange resin particles into porous wafer substrates. NPJ Clean Water 3:5 Stokes K, Clark K, Odetade D, Hardy M (2023) Goldberg Oppenheimer, P. Advances in lithographic techniques for precision nanostructure fabrication in biomedical applications. Discover Nano 18:153 Perumbilavil S, Sankar P, Priya Rose T, Philip R (2015) White light Z-scan measurements of ultrafast optical nonlinearity in reduced graphene oxide nanosheets in the 400–700 nm region. Appl Phys Lett 107 Johra FT, Lee J-W, Jung W-G (2014) Facile and safe graphene preparation on solution based platform. J Ind Eng Chem 20:2883–2887 Additional Declarations The authors declare no competing interests. Supplementary Files SupportinginformationpreprintHM3.docx Supporting information for Optically-induced electrical nano-patterning 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-8767694","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":584531036,"identity":"6892c221-fc05-42bc-ba95-66172f52cc18","order_by":0,"name":"Hyungmok Joh","email":"","orcid":"","institution":"The University of Texas at Austin","correspondingAuthor":false,"prefix":"","firstName":"Hyungmok","middleName":"","lastName":"Joh","suffix":""},{"id":584531037,"identity":"dc32e3ba-cd55-4994-9bc3-bafaba76573f","order_by":1,"name":"Bin Lian","email":"","orcid":"","institution":"The University of Texas at Austin","correspondingAuthor":false,"prefix":"","firstName":"Bin","middleName":"","lastName":"Lian","suffix":""},{"id":584531038,"identity":"31f3f716-78db-47c8-966b-7a5c5b425b5b","order_by":2,"name":"Nolan Cummins","email":"","orcid":"","institution":"The University of Texas at Austin","correspondingAuthor":false,"prefix":"","firstName":"Nolan","middleName":"","lastName":"Cummins","suffix":""},{"id":584531039,"identity":"536891a9-0e98-4b69-b598-657a326cee46","order_by":3,"name":"Jiazheng Bao","email":"","orcid":"","institution":"The University of Texas at Austin","correspondingAuthor":false,"prefix":"","firstName":"Jiazheng","middleName":"","lastName":"Bao","suffix":""},{"id":584531040,"identity":"96c57b3e-c5e3-4b92-aa07-f85bab63615e","order_by":4,"name":"Jang-Hwan Han","email":"","orcid":"","institution":"Heidelberg University","correspondingAuthor":false,"prefix":"","firstName":"Jang-Hwan","middleName":"","lastName":"Han","suffix":""},{"id":584531041,"identity":"313405da-9c47-4724-a3f9-993102c0329a","order_by":5,"name":"Peer Fischer","email":"","orcid":"","institution":"Heidelberg University","correspondingAuthor":false,"prefix":"","firstName":"Peer","middleName":"","lastName":"Fischer","suffix":""},{"id":584531042,"identity":"2c30e7ae-8afb-4ada-ab8c-80b9c716e6d1","order_by":6,"name":"Donglei Emma Fan","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9ElEQVRIiWNgGAWjYDCCwwcYGD6AGMzIojz4tBxLYGCcAVIE1pJApBZmHrgiYrTwHWN+9tim5rC9PTvvAWbeHzaJ/f0HGB+8bcOtRfIYm7lxzrHDiT3MfAnMPAlpxhI3EpgN5+LRYnC/wUw6h+1wAg8zjwFQy2E5hhsMbNK8+LQcY/8mbfHvsD1Uy38e+fMH2H/j18JjJs3YdpixB6LlgJzBgQQ2ZnxaJI/xlEn29qUn9hzmMTg4Jy3Z2PBGYrPknHO4tfAdY98m8eObtT17/xnDB29s7BLnnT988MObMtxaUMABCMXYQKT6UTAKRsEoGAW4AACgJkoLkHTTyAAAAABJRU5ErkJggg==","orcid":"","institution":"The University of Texas at Austin","correspondingAuthor":true,"prefix":"","firstName":"Donglei","middleName":"Emma","lastName":"Fan","suffix":""}],"badges":[],"createdAt":"2026-02-02 17:23:00","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-8767694/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8767694/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":101839263,"identity":"f736aa19-66fc-4e64-a493-9480749b5258","added_by":"auto","created_at":"2026-02-04 08:15:02","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":6342831,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eFigure 1. Experimental Setup. \u003c/strong\u003e\u003c/em\u003e\u003cem\u003e(A) A single 532 nm Laser is expanded and covers the entire DLP mirror, which dynamically project designed light patterns. (B) When a light pattern and electric field is applied, (C) particles deposit to the surface of the a-Si.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-8767694/v1/fd8dfbbb380dfd7756dec470.png"},{"id":101881838,"identity":"553e87cf-4c6f-4e49-9a83-0564c7c1f282","added_by":"auto","created_at":"2026-02-04 15:16:58","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":5025013,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eFigure 2. Characterization.\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e Density of deposited particles plotted against (A) light intensity, (B) waiting time after E-field application, (C) AC Vpp, (D) applied E-field time, (E) AC frequency and (F) salt concentration. (G) Demonstration of positive particle patterning. (H) Change of deposited particles with number of applied E-field bursts. (I) Negative particle patterning achieved by controlling the number of applied E-field bursts. (J) Deposition, (K) removal, and (L) additional deposition of particles after applying an additional PDDA/PSS bi-layer.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-8767694/v1/ad1c77146e1b0df44968ae2c.png"},{"id":101839265,"identity":"f9d3b5b3-db87-4f28-ad4d-2134bd72b8a1","added_by":"auto","created_at":"2026-02-04 08:15:02","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1210694,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eFigure 3. Resolution determination.\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e (A) Single lines with controlled widths and heights were used for resolution determination. (B) Frequency of the E-field results in different output accuracy. (C) Resolution determination using optimized frequency (3 kHz).\u003c/em\u003e\u003c/p\u003e","description":"","filename":"Figure3preprint.png","url":"https://assets-eu.researchsquare.com/files/rs-8767694/v1/dcafedef51f56a7f0c627fdc.png"},{"id":101839268,"identity":"16f9b2dc-b712-4b90-ab1c-591c16957d34","added_by":"auto","created_at":"2026-02-04 08:15:02","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":24294416,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eFigure 4. Multi-material deposition. \u003c/strong\u003e\u003c/em\u003e\u003cem\u003eAssembly of (A) Bacillus Subtilis cells, (B) 100 nm Au particles, (C) silver nanowires, (D) graphene oxide and (E) its Raman peaks, (F) lines of Na\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eSO\u003c/em\u003e\u003csub\u003e\u003cem\u003e4\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e salt (inset: EDX results of (top) Na and (bottom) S, respectively), (G) salmon sperm DNA, (H) P53 and (I) IL-6 antibody proteins.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-8767694/v1/77d5923290745d8131c8d41c.png"},{"id":101881233,"identity":"f41937eb-b0f9-4f25-b10f-74fb6f1e30f4","added_by":"auto","created_at":"2026-02-04 15:11:01","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":4213986,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eFigure 5. Large scale deposition.\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e (A) cm-scale deposition of a Bevo consisting of (B) smaller Bevo patterns (Bevo is UT-Austin’s copyrighted logo).(A – inset) Deposition of the Max Planck Society’s logo.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"Figure5.png","url":"https://assets-eu.researchsquare.com/files/rs-8767694/v1/f6a6ecdc8eead37d69763393.png"},{"id":101882525,"identity":"d2bb4bb4-9ed0-43cc-8ec8-1ea6224f71e8","added_by":"auto","created_at":"2026-02-04 15:23:30","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":42506589,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8767694/v1/853305ad-c720-4996-a54f-0cd96971182e.pdf"},{"id":101881755,"identity":"f72c50d6-677b-4992-a522-5bf11dc6a902","added_by":"auto","created_at":"2026-02-04 15:16:13","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":9713089,"visible":true,"origin":"","legend":"\u003cp\u003eSupporting information for Optically-induced electrical nano-patterning\u003c/p\u003e","description":"","filename":"SupportinginformationpreprintHM3.docx","url":"https://assets-eu.researchsquare.com/files/rs-8767694/v1/5fdf6fc14d27b47d68e8efff.docx"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eOptically-induced electrical nano-patterning\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003ePatterning of materials is a widely employed technology that is essential in many diverse fields ranging from communication to device fabrication. Common to almost all applications, is the need to attain high resolution, fast printing speeds and ideally an ability to organize and position a wide range of materials. The latter is for instance essential when realizing biomedical sensing and array technologies. In comparison with serial processing, parallel methods are especially promising, when large area patterning is of importance. Considerable effort has been invested to address the need for high resolution using top-down lithography-based approaches, including photolithography, electron-beam lithography, and nanoimprint lithography. These techniques provide excellent pattern fidelity and precision, which have been widely combined with standard deposition and lift-off processes, surface functionalization, or templated trapping for placing nanoparticles and molecules. However, they typically require sophisticated instrumentation, multiple processing steps, cleanroom infrastructure, and material-specific chemicals, and in the case of electron beam lithography, advanced technical skills. A major limitation is that they require specific polymeric resists. For instance, it is impossible to print live or biological materials with these techniques.\u003c/p\u003e \u003cp\u003eBeyond conventional lithography,\u003csup\u003e1\u0026ndash;3\u003c/sup\u003e a variety of advanced strategies have been explored. Atomic Force Microscopy (AFM) enabled techniques, such as dip-pen nanolithography and related scanning probe methods, allow nanometer-scale placement of molecules and nanoparticles with exceptional precision, but due to their mostly serial nature are difficult to scale to larger print sizes. \u003csup\u003e4\u0026ndash;6\u003c/sup\u003e Photochemical and photoactivated approaches employ light to locally trigger chemical reactions, binding, or crosslinking, enabling maskless patterning. While highly attractive due to their scalability, these methods are often restricted by specific photochemistries, limited ink diversity, and trade-offs between resolution and throughput. Given the constraints, there is a need for a parallel patterning method that affords high spatial resolution and broad material compatibility.\u003c/p\u003e \u003cp\u003eIn this work, we introduce a novel optically-induced electrical nano-printing method that enables patterning of a diverse range of materials over centimeter-scales with a spatial resolution of ~\u0026thinsp;280 nm. The method relies on light-induced electrical activation of a surface, which in turn triggers the deposition of a broad range of functional inks. Modest light intensities are used to activate the substrate onto which inorganic nanoparticles (metals, polymers, and 2D materials), biomolecules (DNA, proteins, and cancer biomarkers), and even living bacterial cells can then be deposited. The particle size spans six orders of magnitude, from micrometers for bacteria down to a few nanometers for proteins.\u003c/p\u003e \u003cp\u003eEven photorealistic nanopaintings can be achieved by the method which relies on the application of kilohertz (kHz)-range AC electric fields to a photosensitive amorphous silicon (a-Si) surface within an electrochemical cell (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The target ink or material, dispersed in an aqueous ionic support electrolyte (e.g., sodium sulfate), is then effectively deposited in the shape of the projected light images. The light-activation utilizes a digital light projector (DLP). Depending on the functionalization of the of the a-Si, the surface charge can be controlled. When functionalized with polyelectrolyte layers, PDDA yields positively charged surfaces, while PDDA/PSS produces negatively charged interfaces.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e Surprisingly, only ink constituents carrying the same charge polarity are selectively deposited in light-defined regions.\u003c/p\u003e \u003cp\u003eAlternately, it is also possible to use the method for light-directed removal (etching) of deposited materials. The combined deposition and etching yields feature sizes down to 278 nm using a standard microscope objective.\u003c/p\u003e \u003cp\u003eDistinct from prior approaches, the reported technique can readily be used to form centimeter-scale patterns with sub-micrometer precision, for a very broad range of materials. The technique does not require physical masks, specialized biochemicals, ultraviolet illumination, or vacuum processing\u0026mdash;constraints that commonly limit existing nanopatterning methods (\u003cb\u003eTable S1\u003c/b\u003e).\u003c/p\u003e"},{"header":"2. Working Mechanism, Characterization, and Optimization","content":"\u003cp\u003eTo understand the working mechanism, we systematically examine and characterize the effects of key components in the system (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e): (1) The a-Si layer, where the conductivity changes with the light pattern and selectively allows the light-controlled application of electric fields; (2) the polyelectrolyte layer, where charges are primarily stored and particles are deposited as a result of the \u003cem\u003eE\u003c/em\u003e-field; (3) the solution, where the conductivity is determined by the salt concentration; and (4) the applied electric field itself, which governs the efficiency of particle deposition. As will be discussed below, the observed phenomena result not from a single component but from the combined effects of the entire system.\u003c/p\u003e \u003cp\u003eUpon \u003cem\u003eE\u003c/em\u003e-field application during light illumination, particles inside the solution gradually deposit onto the surface. Here, we use the density of the deposited particles (DDP) as a measure for the amount deposited, which critically depends on the amount of charge accumulated in and near the polyelectrolyte layer that enable the assembly.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. The a-Si layer\u003c/h2\u003e \u003cp\u003eThe DDP increases linearly as a function of the applied light intensity (\u003cem\u003eE\u003c/em\u003e-field: 12 Vpp, 1.5 kHz, 200 ms, waiting time after \u003cem\u003eE\u003c/em\u003e-field application: 30 min+), as is seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA. This agrees with the dependence of the photocurrent (\u003cem\u003ei\u003c/em\u003e\u003csub\u003e\u003cem\u003ep\u003c/em\u003e\u003c/sub\u003e) on the photon rate (\u003cem\u003eN\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e) \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:{i}_{p}=e{N}_{0}\\left(1-R\\right)\\left[1-\\text{exp}\\left(-\\alpha\\:d\\right)\\right]\\text{\u0026eta;\u0026tau;/}{t}_{t}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere \u003cem\u003eR\u003c/em\u003e, \u003cem\u003eα\u003c/em\u003e, \u003cem\u003ed\u003c/em\u003e, \u003cem\u003eη\u003c/em\u003e, \u003cem\u003eτ\u003c/em\u003e, \u003cem\u003eand t\u003c/em\u003e\u003csub\u003e\u003cem\u003et\u003c/em\u003e\u003c/sub\u003e are the surface reflection, surface absorption coefficient and depth, electron-hole pair generation efficiency, recombination lifetime, and carrier transit time, respectively. Negatively-charged 200nm polystyrene nanospheres can be assembled as a monolayer on a PDDA/PSS functionalized a-Si surface with a saturation DPP of ~\u0026thinsp;3.5 particles/\u0026micro;m\u003csup\u003e2\u003c/sup\u003e (at ~\u0026thinsp;650 mW/cm\u003csup\u003e2\u003c/sup\u003e). At the lower intensity of 250 mW/cm\u003csup\u003e2\u003c/sup\u003e we obtain a DDP of ~\u0026thinsp;1 particle/\u0026micro;m\u003csup\u003e2\u003c/sup\u003e, which indicates that it is possible to tune the density (gray scale) during printing. In the subsequent discussion we employ an intensity of 790 mW/cm\u003csup\u003e2\u003c/sup\u003e, unless indicated otherwise.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. The polyelectrolyte layer\u003c/h2\u003e \u003cp\u003eThe saturation DDP value increases with the number of polyelectrolyte bi-layers made of PDDA/PSS, with ~\u0026thinsp;3.5, 9, and 14 particles /\u0026micro;m\u003csup\u003e2\u003c/sup\u003ecorresponding to single, double, and triple layers, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). We note that after applying an \u003cem\u003eE\u003c/em\u003e-field burst (E-field: 12 Vpp, 1.5 kHz, 200 ms, and a light intensity of 790 mW/cm\u003csup\u003e2\u003c/sup\u003e), the DDP gradually increases with time and plateaus at ~\u0026thinsp;30min for all conditions.\u003c/p\u003e \u003cp\u003eInterestingly, when we change the outermost functionalization layer to PDDA,\u003csup\u003e11\u003c/sup\u003e a positively charged polyelectrolyte, only positively-charged particles can be deposited onto the areas that are illuminated (\u003cb\u003eFig. S1\u003c/b\u003e). Similarly, negatively-charged particles deposit on PSS-terminated surfaces (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eH). Surprisingly, oppositely charged particles in suspension are not attracted to the surface. For instance, negatively-charged particles are repelled from the light-illuminated PDDA-terminated surfaces, as shown in the darkened area in \u003cb\u003eFig. S2\u003c/b\u003e. The strong dependance of DDP on both the relative charge polarity of particle-surface pair and waiting time indicates that the working mechanism is based on electrostatics. The light-triggered polyelectrolyte-functionalized a-Si surface reverses its charge polarity. To determine if the working mechanism is only limited to a-Si surfaces, we also perform the same study on metal surfaces, such as Cu foam films (\u003cb\u003eFig. S3\u003c/b\u003e). The results clearly indicate the same particle assembly effect as that observed on a-Si, further illustrating the generalizability of the working principle underlying the phenomena.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. The applied E-field\u003c/h2\u003e \u003cp\u003eTo unravel the role of the applied \u003cem\u003eE\u003c/em\u003e-field, we systematically sweep the Vpp, frequency, and the total voltage application time. DDP linearly increases with Vpp and reaches its saturation at ~\u0026thinsp;10 Vpp (1.5 kHz, 200ms, light intensity: 790 mW/cm\u003csup\u003e2\u003c/sup\u003e, waiting time: 30min). No obvious deposition is observed for Vpp values lower than 6 Vpp (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC). Similarly, DDP monotonically increases with the total time of the applied \u003cem\u003eE\u003c/em\u003e-field (1.5 kHz, 12Vpp, light intensity: 790 mW/cm\u003csup\u003e2\u003c/sup\u003e, waiting time: 30min). Particle deposition starts at only 2 ms (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD, \u003cb\u003einset\u003c/b\u003e) and saturates at 1000\u0026ndash;2000 ms (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD). The experimental parameters of Vpp, \u003cem\u003eE\u003c/em\u003e-field time, and light intensity positively correlate with the charge passing through the electrochemical cell up to a saturation point. This supports that the nature of the particle deposition is enabled by charges and electrostatics. While the DDP decreases with increasing frequency (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eE), at frequencies higher than ~\u0026thinsp;10 kHz particles no longer deposit on the substrate. The results agree with frequency-dependent response of ions in solution, in which ionic transport becomes increasingly ineffective as the applied AC field frequency increases.\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. The electrolyte\u003c/h2\u003e \u003cp\u003eLast, we probe the effect of the electrolyte, specifically the concentration of sodium sulfate ranging from a low 2.5 mM to a high 0.75 M, and its impact on the DDP. As long as particles are stably dispersed,\u003csup\u003e13\u003c/sup\u003e their assembly can be obtained reproducibly spanning all concentrations; the higher the concentration the greater the density. Not only simple electrolytes facilitate the deposition, but also more complex solutions relevant for biological samples, such as phosphate-buffered saline (PBS) also support assembly. This is notably different from previous works on dielectrophoresis (DEP)-enabled assembly, where particle manipulation and assembly mostly benefit from low ionic concentration, and where the effective electric fields applied to particles are greatly reduced in high ionic strengths. To further clarify that the present mechanism differs from DEP-enabled assembly, we examine the particles\u0026rsquo; response in deionized water using the same setup and conditions. Particles are seen to primarily aggregate at the edges of the light patterns where the electric-field density and importantly the electric field gradient is the highest and not in the center of the patterns (which is clearly shown when the electrolyte is present) (\u003cb\u003eFig. S4\u003c/b\u003e).\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e Both our theoretical understanding and experimental results thus indicate that the present method is not based on dielectrophoresis (DEP). Rather, the increase of particle density with ionic concentration suggests that the light-triggered electric charge accumulation and the electrochemical nature of the system drives the pattern process. In an electrochemical cell, the Debye screening length of the electric double layer reduces rapidly with ionic concentration.\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e Higher salt concentration also increases the electrolyte conductivity, causing a larger fraction of the voltage drop at the electric double layer and polyelectrolyte coating, resulting in increased ion transport speed.\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eThe above extensive experimental study clearly reveals the counter charge accumulation in areas of electrolyte layers under light-activation in an AC field. The charge amount increases with the number polyelectrolyte-layer repeats, \u003cem\u003eE\u003c/em\u003e-field time and strength, ionic concentration, and a reduction in the AC-frequency.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Versatile Nanopainting","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1. 2D positive/negative patterning and particle reconfiguration\u003c/h2\u003e \u003cp\u003eWe show that the method can be used to create images. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eG, we paint a rose using 200-nm polystyrene nanoparticles. Here we notice that when applying multiple \u003cem\u003eE\u003c/em\u003e-field bursts, a linear DDP increase is observed until 10 bursts, where a plateau is reached, agreeing with the results in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD. However, with 30\u0026thinsp;+\u0026thinsp;bursts, the assembled particles gradually start to desorb from the surface with the number of subsequent \u003cem\u003eE\u003c/em\u003e-field bursts (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eH, \u003cb\u003eSupporting notes\u003c/b\u003e), showcasing the technique\u0026rsquo;s ability to not only deposit but also etch patterns. Therefore, we also successfully create negative images of the same rose by first depositing a uniform background followed by light-controlled etching (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eI). Here, for double and triple PDDA/PSS bi-layers, the nanoparticles maintain their adhesion even after 50\u0026thinsp;+\u0026thinsp;bursts, likely due to their increased adhesion to the a-Si surface. It should be noted that by applying an additional polyelectrolyte layer after etching, it becomes possible to redeposited particles at light-directed regions, paving the way for reconfigurable patterning (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eJ \u003cb\u003eto L\u003c/b\u003e). Last but not least, the technique is not restricted to single-layer 2D painting. By simply adding additional PDDA/PSS bi-layers on the nanopatterns, we readily create the second and third layers of patterns (\u003cb\u003eFig. S5\u003c/b\u003e), which allows for 2.5-3D assembly.\u003c/p\u003e \u003cp\u003e \u003cb\u003eResolution and optimization\u003c/b\u003e \u003c/p\u003e \u003cp\u003eAs is the case of any printing technology, patterning resolution is a key characteristic that determines the clarity and precision of the final output.\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e Here, we determine the resolution by printing an array of line patterns of varying widths and lengths (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). We note that a change of the \u003cem\u003eE\u003c/em\u003e-field frequency also slightly affects the output pattern size. When printing a square pattern with a fixed length value from the DLP device (=\u0026thinsp;target length), the resulting output shows a linear decrease in the pattern\u0026rsquo;s length with increased frequency (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB). We find that 3 kHz generates a close match to the intended target length, which we therefore use for the resolution characterization below. For an ideal system, we can expect a 1:1 correspondence of DLP input pixel and the length of the deposited particles, meaning a y-axis intercept of 0 and a slope that would match the DLP-limited resolution. Experimentally, we obtain an intercept of 0.11, corresponding to ~\u0026thinsp;110 nm, and a slope of 0.56, corresponding to ~\u0026thinsp;560 nm, the resolution of the technique, agreeing with that of DLP minimum pixel size (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC). This resolution can be further improved by using an improved DLP system (more mirrors, increasing the resolution) and higher laser power (adequate light even at the smallest pixel sizes). When combining both deposition and etching, we create line patterns with a precision of 278 nm (\u003cb\u003eFig. S6\u003c/b\u003e), effectively matching the Abbe criterion expected for a 532 nm light source (=\u0026thinsp;266 nm). This corresponds to a patterning resolution that exceeds 90,000 dots per inch.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Multiplex assembly\u003c/h2\u003e \u003cp\u003eThe technique is highly versatile and is compatible with diverse inks. For demonstration, we deposit \u0026micro;m long B. Subtilis bacterial cells (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA) as well as nm-scale Au particles (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB), and complex Ag/SiO\u003csub\u003e2\u003c/sub\u003e nanoparticle composites (\u003cb\u003eFig. S7\u003c/b\u003e), Ag nanowires (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eC) and graphene oxide nanosheets (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eD \u003cb\u003eand E\u003c/b\u003e). We also show that even salt (Na\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e) dissolved in solution (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eF) can precipitate owing to the locally enhanced ion concentration. While the bacterial cells are directly observable via SEM, Au nanoparticles, graphene oxide nanosheets, are verified by using dark-field and Raman spectroscopy (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eE), respectively. In particular, graphene oxide patterning is confirmed by the D and G bands in the Raman scattering\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e and Na\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e is confirmed by EDX measurements (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eF, \u003cb\u003einset\u003c/b\u003e). It is also possible to pattern DNA (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eG) and proteins (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eH \u003cb\u003eand I\u003c/b\u003e), showing potential high-throughput analysis of molecular interactions, gene expression, and biomarker detection in biomedical assays and diagnostics. As a proof-of-concept, we demonstrate the co-deposition of P53, IL-6 antibody proteins onto a single chip (\u003cb\u003eFig. S8\u003c/b\u003e), as well as dense arrays protein arrays made of IL-6 antibodies (\u003cb\u003eFig. S9\u003c/b\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Large-scale particle deposition\u003c/h2\u003e \u003cp\u003eFinally, we evaluate the scalability of the deposition method. We demonstrate centimeter-scale particle patterning with a feature size of \u0026lt;\u0026thinsp;10 \u0026micro;m. The large-scale pattern is made using a single pattern as a \u0026ldquo;stamp\u0026rdquo;, while moving the stage and applying an E-field burst at each step. Alternatively, the electric field can be applied continuously, while patterns are created only in areas under light exposure, comparable to direct inkjet printing. For the former, we demonstrate a \u0026ldquo;Bevo\u0026rdquo; pattern, 1 cm x 0.5 cm wide (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eA), made of numerous \u0026ldquo;Bevo\u0026rdquo; stamps (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB).\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn this work, we report a novel, simple solution-based approach for particle deposition, based on charged polyelectrolyte layers and AC electric fields. The deposition area is activated by visible light, where the light pattern is formed using a projector paired with a photoconductive silicon surface. The quantity of particles deposited can be precisely controlled by changing the electric field, light intensity, and salt concentration. We show that a variety of functional and practical materials can be deposited, from cells to metallic nanoparticles and nanowires, DNA and proteins, and even salt. Finally, we demonstrate that the technique is highly scalable allowing cm-scale particle patterning. We anticipate that this technology will be used in a wide range of applications.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eGallatin GM, Liddle JA (2024) Photolithography: capabilities and limitations\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHarriott LR (2001) Limits of lithography. \u003cem\u003eProceedings of the IEEE\u003c/em\u003e 89, 366\u0026ndash;374\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHoeneisen B, Mead CA (1972) Fundamental limitations in microelectronics\u0026mdash;I. MOS technology. Solid State Electron 15:819\u0026ndash;829\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMuldoon K, Song Y, Ahmad Z, Chen X, Chang M-W (2022) High Precision 3D Printing for Micro to Nano Scale Biomedical and Electronic Devices. Micromachines (Basel) 13:642\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBhagoria P, Mathew Sebastian E, Kumar Jain S, Purohit J, Purohit R (2020) Nanolithography and its alternate techniques. \u003cem\u003eMater. Today Proc.\u003c/em\u003e 26, 3048\u0026ndash;3053\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJaiswal A et al (2023) Two decades of two-photon lithography: Materials science perspective for additive manufacturing of 2D/3D nano-microstructures. iScience 26:106374\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarad H-N, Kwon H, Alarc\u0026oacute;n-Correa M, Fischer P (2021) Large Area Patterning of Nanoparticles and Nanostructures: Current Status and Future Prospects. ACS Nano 15:5861\u0026ndash;5875\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCampbell J, Vikulina AS (2020) Layer-By-Layer Assemblies of Biopolymers: Build-Up, Mechanical Stability and Molecular Dynamics. Polym (Basel) 12:1949\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchlenoff JB, Dubas ST (2001) Mechanism of Polyelectrolyte Multilayer Growth: Charge Overcompensation and Distribution. Macromolecules 34:592\u0026ndash;598\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLoveland RJ, Spear WE, Al-Sharbaty A (1973) Photoconductivity and absorption in amorphous Si. J Non Cryst Solids 13:55\u0026ndash;68\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYin Y, Chen M, Zhou S, Wu L (2012) A general and feasible method for the fabrication of functional nanoparticles in mesoporous silica hollow composite spheres. J Mater Chem 22:11245\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBard AJ, Faulkner LR, White HS (2022) Electrochemical Methods: Fundamentals and Applications. John Wiley \u0026amp; Sons, Ltd.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGentili D, Ori G (2022) Reversible assembly of nanoparticles: theory, strategies and computational simulations. Nanoscale 14:14385\u0026ndash;14432\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMondal TK, Bangaru AVB, Williams SJ (2025) A Review on AC-Dielectrophoresis of Nanoparticles. Micromachines (Basel) 16:453\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003e\u003cem\u003eColloidal Dispersions\u003c/em\u003e. (Cambridge University Press, (2012)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang W, Chen X, Wang Y, Wu L, Hu Y (2020) Experimental and Modeling of Conductivity for Electrolyte Solution Systems. ACS Omega 5:22465\u0026ndash;22474\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen M et al (2024) Application of polyelectrolytes for contaminant removal and recovery during water and wastewater treatment: A critical review. J Water Process Eng 64:105528\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWeidlich C, Mangold K-M, J\u0026uuml;ttner K (2001) Conducting polymers as ion-exchangers for water purification. Electrochim Acta 47:741\u0026ndash;745\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePalakkal VM et al (2020) Advancing electrodeionization with conductive ionomer binders that immobilize ion-exchange resin particles into porous wafer substrates. NPJ Clean Water 3:5\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStokes K, Clark K, Odetade D, Hardy M (2023) Goldberg Oppenheimer, P. Advances in lithographic techniques for precision nanostructure fabrication in biomedical applications. Discover Nano 18:153\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePerumbilavil S, Sankar P, Priya Rose T, Philip R (2015) White light Z-scan measurements of ultrafast optical nonlinearity in reduced graphene oxide nanosheets in the 400\u0026ndash;700 nm region. Appl Phys Lett 107\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJohra FT, Lee J-W, Jung W-G (2014) Facile and safe graphene preparation on solution based platform. J Ind Eng Chem 20:2883\u0026ndash;2887\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"The University of Texas at Austin","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":"nano-patterning, large-scale printing, 2D printing, semi-3D printing","lastPublishedDoi":"10.21203/rs.3.rs-8767694/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8767694/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eMicro- and nanopatterning techniques are essential for fabricating next-generation devices in electronics, photonics, and biotechnology, as they dictate material properties, surface interactions, and device performance through precise structural control at critical scales. These methods underlie the development of multiple innovations, such as high-density sensors, lab-on-a-chip systems, and advanced screening platforms used in molecular biology. However, current patterning methods often face limitations in scalability, cost, and compatibility with sensitive materials. Here, we demonstrate an optically-induced electrical nano-painting technique that enables pattern formation over centimeter-scale areas with ~\u0026thinsp;280 nm spatial precision. Operating at light intensities comparable to sunlight, this scalable method is compatible with a broad range of functional inks including live bacterial cells, inorganic nanoparticles, biomolecules, and ionic compounds.\u003c/p\u003e","manuscriptTitle":"Optically-induced electrical nano-patterning","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-04 08:14:46","doi":"10.21203/rs.3.rs-8767694/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":"7d69521c-aabe-4667-bda7-a94641c05bdc","owner":[],"postedDate":"February 4th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":62183902,"name":"Materials Engineering"}],"tags":[],"updatedAt":"2026-02-04T08:14:46+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-04 08:14:46","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8767694","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8767694","identity":"rs-8767694","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}