MI/
Articles/
2509001201
  • Open Access
  • Article

Angle-Independent Surface-Instability Hydrogel Sensors Enabled by Thickness Control

  • Ruoyi Ke †,   
  • Imri Frenkel †,   
  • Zixiao Liu,   
  • Chuan Wei Zhang,   
  • Ping He,   
  • Pengju Shi,   
  • Abdullatif Jazzar,   
  • Yousif Alsaid,   
  • Yingjie Du,   
  • Sidi Duan,   
  • Dong Wu,   
  • Mutian Hua,   
  • Shuwang Wu,   
  • Ximin He *

Received: 09 Jul 2025 | Revised: 26 Aug 2025 | Accepted: 01 Sep 2025 | Published: 04 Sep 2025

Abstract

Surface instability-based hydrogel sensors offer equipment-free visual detection but suffer from severe angle-dependent visibility that limits practical applications. Here we demonstrate that film thickness serves as a critical fourth design parameter—beyond elastic modulus, swelling ratio, and stimulus concentration—to achieve omnidirectional optical readout. Through systematic optimization across poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA), poly(acrylamide-co-acrylic acid) (P(AAm-co-AAc)), and poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAm-co-Am)) systems, we identify an operational thickness window of 160–1300 μm, with 300 μm producing wrinkle dimensions that match visible light wavelengths for angle-independent scattering. This morphological control reduces viewing angle effects by >80%, enabling reliable naked-eye detection across a wide viewing angle range (0–60°), representing an >80% improvement over previous angle-dependent sensors. We validate this design framework through enzyme-coupled glucose sensors operating across clinical ranges (200–1000 mg/dL) and direct polarity sensors with binary discrimination at Polarity Index (PI) ~3.5. Exploiting the threshold nature of instability-induced scattering (IIS), we further demonstrate soft material logic gates (AND, OR, XOR) that process environmental stimuli and autonomously control LCE actuators within 15 s—establishing the examples of hydrogel-based Boolean computation without electronic components. These advances transform IIS sensors from laboratory curiosities into practical platforms for soft robotics and autonomous systems.

Graphical Abstract

Image Viewer
Open in new tab
Download Image

References 

  • 1.
    Ates, H.C.; Nguyen, P.Q.; Gonzalez-Macia, L.; Morales-Narvaez, E.; Guder, F.; Collins, J.J.; Dincer, C. End-to-end design of wearable sensors. Nat. Rev. Mater. 2022, 7, 887–907.
  • 2.
    Zhao, D.; Zhu, Y.; Cheng, W.; Chen, W.; Wu, Y.; Yu, H. Cellulose-Based Flexible Functional Materials for Emerging Intelligent Electronics. Adv. Mater. 2021, 33, e2000619.
  • 3.
    McEvoy, M.A.; Correll, N. Materials science. Materials that couple sensing, actuation, computation, and communication. Science 2015, 347, 1261689.
  • 4.
    Qian, X.; Zhao, Y.; Alsaid, Y.; Wang, X.; Hua, M.; Galy, T.; Gopalakrishna, H.; Yang, Y.; Cui, J.; Liu, N.; et al. Artificial phototropism for omnidirectional tracking and harvesting of light. Nat. Nanotechnol. 2019, 14, 1048–1055.
  • 5.
    Pedro, D.I.; Nguyen, D.T.; Trachsel, L.; Rosa, J.G.; Chu, B.; Eikenberry, S.; Sumerlin, B.S.; Sawyer, W.G. Superficial Modulus, Water-Content, and Mesh-Size at Hydrogel Surfaces. Tribol. Lett. 2021, 69. 160.
  • 6.
    Zhao, Y.; Lo, C.Y.; Ruan, L.; Pi, C.H.; Kim, C.; Alsaid, Y.; He, X. Somatosensory actuator based on stretchable conductive photothermally responsive hydrogel. Sci. Robot. 2021, 6, eabd5483.
  • 7.
    Zhao, Y.; Hua, M.; Yan, Y.; Wu, S.; Alsaid, Y.; He, X. Stimuli-Responsive Polymers for Soft Robotics. Annu. Rev. Control Robot. Auton. Syst. 2022, 5, 515–545.
  • 8.
    Hoffman, A.S. Hydrogels for biomedical applications. Adv. Drug Deliv. Rev. 2012, 64, 18–23.
  • 9.
    Cai, Z.; Luck, L.A.; Punihaole, D.; Madura, J.D.; Asher, S.A. Photonic crystal protein hydrogel sensor materials enabled by conformationally induced volume phase transition. Chem. Sci. 2016, 7, 4557–4562.
  • 10.
    Dušková-Smrčková, M.; Dušek, K. How to Force Polymer Gels to Show Volume Phase Transitions. ACS Macro Lett. 2019, 8, 272–278.
  • 11.
    Walker, J.P.; Asher, S.A. Acetylcholinesterase-Based Organophosphate Nerve Agent Sensing Photonic Crystal. Anal. Chem. 2005, 77, 1596–1600.
  • 12.
    Ferreira, L.; Vidal, M.M.; Gil, M.H. Evaluation of poly(2-hydroxyethyl methacrylate) gels as drug delivery systems at different pH values. Int. J. Pharm. 2000, 194, 169–180.
  • 13.
    Nakayama, M.; Yamada, N.; Kumashiro, Y.; Kanazawa, H.; Yamato, M.; Okano, T. Thermoresponsive poly(N-isopropylacrylamide)-based block copolymer coating for optimizing cell sheet fabrication. Macromol. Biosci. 2012, 12, 751–760.
  • 14.
    Yetisen, A.K.; Jiang, N.; Fallahi, A.; Montelongo, Y.; Ruiz-Esparza, G.U.; Tamayol, A.; Zhang, Y.S.; Mahmood, I.; Yang, S.-A.; Kim, K.S.; et al. Glucose-sensitive hydrogel optical fibers functionalized with phenylboronic acid. Adv. Mater. 2017, 29, 1606380.
  • 15.
    Choi, M.; Humar, M.; Kim, S.; Yun, S.-H. Step-Index Optical Fiber Made of Biocompatible Hydrogels. Adv. Mater. 2015, 27, 4081–4086.
  • 16.
    Wang, Z.; Zhang, W.; Liu, X.; Li, M.; Lang, X.; Singh, R.; Marques, C.; Zhang, B.; Kumar, S. Novel Optical Fiber-Based Structures for Plasmonics Sensors. Biosensors 2022, 12, 1016.
  • 17.
    Ling, Z.; Chen, J.; Li, S.; Lu, H.; Du, J.; Liu, Z.; Qiu, J. A multi-band stealth and anti-interference superspeed light-guided swimming robot based on multiscale bicontinuous three-dimensional network. Chem. Eng. J. 2024, 485, 150094.
  • 18.
    Zhang, C.W.; Chen, C.; Duan, S.; Yan, Y.; He, P.; He, X. Hydrogel-based soft bioelectronics for personalized healthcare. Med-X 2024, 2, 20.
  • 19.
    Yang, S.; Sarkar, S.; Xie, X.; Li, D.; Chen, J. Application of Optical Hydrogels in Environmental Sensing. Energy Environ. Mater. 2024, 7, e12646.
  • 20.
    Cao, H.; Duan, L.; Zhang, Y.; Cao, J.; Zhang, K. Current hydrogel advances in physicochemical and biological response-driven biomedical application diversity. Signal Transduct. Target. Ther. 2021, 6, 426.
  • 21.
    Yetisen, A.K.; Butt, H.; Volpatti, L.R.; Pavlichenko, I.; Humar, M.; Kwok, S.J.J.; Koo, H.; Kim, K.S.; Naydenova, I.; Khademhosseini, A.; et al. Photonic hydrogel sensors. Biotechnol. Adv. 2016, 34, 250–271.
  • 22.
    Wang, M.; Yang, Y.; Min, J.; Song, Y.; Tu, J.; Mukasa, D.; Ye, C.; Xu, C.; Heflin, N.; McCune, J.S.; et al. A wearable electrochemical biosensor for the monitoring of metabolites and nutrients. Nat. Biomed. Eng. 2022, 6, 1225–1235.
  • 23.
    Sun, S.; Chen, J. Recent Advances in Hydrogel-Based Biosensors for Cancer Detection. ACS Appl. Mater. Interfaces 2024, 16, 46988–47002.
  • 24.
    Shen, P.; Li, M.; Li, R.; Han, B.; Ma, H.; Hou, X.; Zhang, Y.; Wang, J.-J. Aptamer-functionalized smart photonic hydrogels: application for the detection of thrombin in human serum. NPG Asia Mater. 2022, 14, 94.
  • 25.
    Qin, M.; Sun, M.; Hua, M.; He, X. Bioinspired structural color sensors based on responsive soft materials. Curr. Opin. Solid State Mater. Sci. 2019, 23, 13–27.
  • 26.
    Qin, M.; Sun, M.; Bai, R.; Mao, Y.; Qian, X.; Sikka, D.; Zhao, Y.; Qi, H.J.; Suo, Z.; He, X. Bioinspired Hydrogel Interferometer for Adaptive Coloration and Chemical Sensing. Adv. Mater. 2018, 30, 1800468.
  • 27.
    Yang, S.; Tang, Z.; Tian, Y.; Ji, X.; Wang, F.; Xie, C.; He, Z. Dual-Color Fluorescent Hydrogel Microspheres Combined with Smartphones for Visual Detection of Lactate. Biosensors 2022, 12, 802.
  • 28.
    Li, W.; Zhang, X.; Hu, X.; Shi, Y.; Li, Z.; Huang, X.; Zhang, W.; Zhang, D.; Zou, X.; Shi, J. A smartphone-integrated ratiometric fluorescence sensor for visual detection of cadmium ions. J. Hazard. Mater. 2021, 408, 124872.
  • 29.
    Wang, Q.; Zhao, X. Beyond wrinkles: Multimodal surface instabilities for multifunctional patterning. MRS Bull. 2016, 41, 115–122.
  • 30.
    Frenkel, I.; Hua, M.; Alsaid, Y.; He, X. Self-Reporting Hydrogel Sensors Based on Surface Instability-Induced Optical Scattering. Adv. Photonics Res. 2021, 2, 2100058.
  • 31.
    Fan, W.; Zeng, J.; Gan, Q.; Ji, D.; Song, H.; Liu, W.; Shi, L.; Wu, L. Iridescence-controlled and flexibly tunable retroreflective structural color film for smart displays. Sci. Adv. 2019, 5, eaaw8755.
  • 32.
    Lee, K.-L.; Chang, C.-C.; You, M.-L.; Pan, M.-Y.; Wei, P.-K. Enhancing Surface Sensing Sensitivity of Metallic Nanostructures using Blue-Shifted Surface Plasmon Mode and Fano Resonance. Sci. Rep. 2018, 8, 9762.
  • 33.
    Zhang, R.; Yang, Z.; Wang, Q.; Li, W.; Xu, H.; Li, L. Angle dependent structural colors with full-visible-spectrum and narrow-angle change properties for anti-counterfeiting. Dyes Pigm. 2023, 208, 110794.
  • 34.
    Chung, J.Y.; Nolte, A.J.; Stafford, C.M. Surface Wrinkling: A Versatile Platform for Measuring Thin-Film Properties. Adv. Mater. 2011, 23, 349–368.
  • 35.
    Warren, T.J.; Bowles, N.E.; Donaldson Hanna, K.; Bandfield, J.L. Modeling the Angular Dependence of Emissivity of Randomly Rough Surfaces. J. Geophys. Res. Planets 2019, 124, 585–601.
  • 36.
    Gross, P.; Störzer, M.; Fiebig, S.; Clausen, M.; Maret, G.; Aegerter, C.M. A precise method to determine the angular distribution of backscattered light to high angles. Rev. Sci. Instrum. 2007, 78, 033105.
  • 37.
    Considine, P.S.; Cronin, D.J.; Reynolds, G.O. Angular Dependence of Radiance of Rough Surfaces in Imaging Systems. J. Opt. Soc. Am. 1966, 56, 877–883.
  • 38.
    Chen, C.; Shi, P.; Liu, Z.; Duan, S.; Si, M.; Zhang, C.; Du, Y.; Yan, Y.; White, T.J.; Kramer-Bottiglio, R.; et al. Advancing physical intelligence for autonomous soft robots. Sci. Robot. 2025, 10, eads1292.
  • 39.
    Zhao, Y.; Li, Q.; Liu, Z.; Alsaid, Y.; Shi, P.; Jawed, M.K.; He, X. Sunlight-powered self-excited oscillators for sustainable autonomous soft robotics. Sci. Robot. 2023, 8, eadf4753.
  • 40.
    Liu, Y.; Tian, G.; Du, Y.; Shi, P.; Li, N.; Li, Y.; Qin, Z.; Jiao, T.; He, X. Highly Stretchable, Low-Hysteresis, and Adhesive TA@MXene-Composited Organohydrogels for Durable Wearable Sensors. Adv. Funct. Mater. 2024, 34, 2315813.
  • 41.
    Zhao, K.; Cao, X.; Alsaid, Y.; Cheng, J.; Wang, Y.; Zhao, Y.; He, X.; Zhang, S.; Niu, W. Interactively mechanochromic electronic textile sensor with rapid and durable electrical/optical response for visualized stretchable electronics. Chem. Eng. J. 2021, 426, 130870.
  • 42.
    Liu, Q.; Nian, G.; Yang, C.; Qu, S.; Suo, Z. Bonding dissimilar polymer networks in various manufacturing processes. Nat. Commun. 2018, 9, 846.
  • 43.
    Yuk, H.; Zhang, T.; Lin, S.; Parada, G.A.; Zhao, X. Tough bonding of hydrogels to diverse non-porous surfaces. Nat. Mater. 2016, 15, 190–196.
  • 44.
    Wirthl, D.; Pichler, R.; Drack, M.; Kettlguber, G.; Moser, R.; Gerstmayr, R.; Hartmann, F.; Bradt, E.; Kaltseis, R.; Kaltenbrunner, M. Instant tough bonding of hydrogels for soft machines and electronics. Sci. Adv. 2017, 3, e1700053.
  • 45.
    Vandeparre, H.; Gabriele, S.; Brau, F.; Gay, C.; Parker, K.K.; Damman, P. Hierarchical wrinkling patterns. Soft Matter. 2010, 6, 5751–5756.
  • 46.
    Li, B.; Cao, Y.-P.; Feng, X.-Q.; Gao, H. Mechanics of morphological instabilities and surface wrinkling in soft materials: a review. Soft Matter. 2012, 8, 5728–5745.
  • 47.
    Kim, H.S.; Crosby, A.J. Solvent-Responsive Surface via Wrinkling Instability. Adv. Mater. 2011, 23, 4188–4192.
  • 48.
    Liu, J.; Jiang, Z.; Li, Y.; Kang, G.; Qu, S. Stability of hydrogel adhesion enabled by siloxane bonds. Eng. Fract. Mech. 2022, 271, 108662.
  • 49.
    Kang, M.K.; Huang, R. Effect of surface tension on swell-induced surface instability of substrate-confined hydrogel layers. Soft Matter. 2010, 6, 5736–5745.
  • 50.
    Auguste, A.; Yang, J.; Jin, L.; Chen, D.; Suo, Z.; Hayward, R.C. Formation of high aspect ratio wrinkles and ridges on elastic bilayers with small thickness contrast. Soft Matter. 2018, 14, 8545–8551.
  • 51.
    Zhou, Y.; Chen, Y.; Jin, L. Three-dimensional postbuckling analysis of thick hyperelastic tubes. J. Mech. Phys. Solids 2023, 173, 105202.
  • 52.
    Kang, C.; Liu, Z.; Chen, S.; Jiang, X. Circular trajectory weaving welding control algorithm based on space transformation principle. J. Manuf. Process. 2019, 46, 328–336.
  • 53.
    Jin, L.; Takei, A.; Hutchinson, J.W. Mechanics of wrinkle/ridge transitions in thin film/substrate systems. J. Mech. Phys. Solids 2015, 81, 22–40.
  • 54.
    Lynch, D.K. Snell’s window in wavy water. Appl. Opt. 2015, 54, B8–B11.
  • 55.
    Young, A.T. Rayleigh scattering. Appl. Opt. 1981, 20, 533–535.
  • 56.
    Schwartz, C.; Dogariu, A. Conservation of angular momentum of light in single scattering. Opt. Express. 2006, 14, 8425–8433.
  • 57.
    Mansuripur, M. Angular Momentum Exchange Between Light and Material Media Deduced from the Doppler Shift. Proc. SPIE 2012, 8458, 20–27.
  • 58.
    Zia, M.A.; Khalil Ur, R.; Kamal, S.M.; Andaleeb, F.; Mahmood, I.R.; Ahmad, S.M.; Khan, I.A.; Ahmad, I.K. Thermal Characterization of Purified Glucose Oxidase from A Newly Isolated Aspergillus Niger UAF-1. J. Clin. Biochem. Nutr. 2007, 41, 132–138.
  • 59.
    Bright, H.J.; Appleby, M. The pH Dependence of the Individual Steps in the Glucose Oxidase Reaction. J. Biol. Chem. 1969, 244, 3625–3634.
  • 60.
    Snyder, L.R. Classification of the solvent properties of common liquids. J. Chromatogr. A 1974, 92, 223–230.
  • 61.
    Acree, W.E.; Lang, A.S.I.D. Reichardt’s Dye-Based Solvent Polarity and Abraham Solvent Parameters: Examining Correlations and Predictive Modeling. Liquids 2023, 3, 303–313.
Share this article:
Download PDF
Supplementary Materials
DOI
10.53941/mi.2025.100026
Issue
Volume 2, Issue 3
How to Cite
Ke, R.; Frenkel, I.; Liu, Z.; Zhang, C. W.; He, P.; Shi, P.; Jazzar, A.; Alsaid, Y.; Du, Y.; Duan, S.; Wu, D.; Hua, M.; Wu, S.; He, X. Angle-Independent Surface-Instability Hydrogel Sensors Enabled by Thickness Control. Materials and Interfaces 2025, 2 (3), 348–360. https://doi.org/10.53941/mi.2025.100026.
RIS
BibTex
Copyright & License
article copyright Image
Copyright (c) 2025 by the authors.