MI/
Articles/
2506000809
  • Open Access
  • Article
An Anisotropic Hydrogel with Simple Preparation and Well-Defined Structure as a New Platform for Flexible Sensors with Directional Strain and Force Sensing
  • Yitong Xie 1, 2,   
  • Shuxu Wang 1, *,   
  • Yunlei Zhang 1,   
  • Hayato Kanai 1,   
  • Kuniyo Yamada 1,   
  • Toshie Wakamatsu 1,   
  • Yuko Hamada 1,   
  • Sei Obuse 1,   
  • Daihui Zhang 2,   
  • Fuxiang Chu 2,   
  • Yasuhiro Ishida 1, *

Received: 10 Apr 2025 | Revised: 16 Jun 2025 | Accepted: 18 Jun 2025 | Published: 25 Jun 2025

Abstract

As a platform to construct the next-generation flexible strain and force sensors, anisotropic hydrogels have recently attracted considerable attention, with an expectation that they would visualize the anisotropic motion of biological systems in a direction-specific manner. To date, a number of anisotropic hydrogels have been developed with an intensive pursuit to improve their practical performance, so that their composition, preparation, and structure have become increasingly complex over the years. In fact, most of these anisotropic hydrogels are prepared from many components including naturally occurring materials, using multiple steps that often require skillful control of kinetic events. Therefore, although some of them show good performances, their complicated and unclear structures make it difficult to elucidate the relationship between structure and properties. As an approach complementary to such trend, here we report a very simple anisotropic hydrogel that would provide a versatile platform for flexible sensors with directional sensing capability. This hydrogel was simply prepared by one-pot reaction from two components, i.e., by magnetic orientation of titanate nanosheet (TiNS) in water and subsequent in-situ formation of a polyacrylamide network. In the resulting hydrogel (TiNS-gel), TiNS platelets were arranged in a lamellar structure with highly oriented, periodic, and homogeneous state. Due to such structure, TiNS-gel exhibited remarkable anisotropy in tensile modulus, nanostructural transformability, and ionic conductivity. Furthermore, TiNS-gel changed its electrical resistance upon tensile deformation, demonstrating its potential utility as a flexible strain and force sensor. TiNS-gel, characterized by easy synthesis, simple composition, well-defined structure, and various anisotropic properties will serve as a useful platform for developing flexible devices with direction-selective strain and force sensing capabilities.

Graphical Abstract

Image Viewer
Open in new tab
Download Image

References 

  • 1.
    Zhang, Z.; Yang, J.; Wang, H.; Wang, C.; Gu, Y.; Xu, Y.; Lee, S.; Yokota, T.; Haick, H.; Someya, T.; et al. A 10-micrometer-thick nanomesh-reinforced gas-permeable hydrogel skin sensor for long-term electrophysiological monitoring. Sci. Adv. 2024, 10, eadj5389.
  • 2.
    Li, Y.; Liu, C.; Zou, H.; Che, L.; Sun, P.; Yan, J.; Liu, W.; Xu, Z.; Yang, W.; Dong, L.; et al. Integrated wearable smart sensor system for real-time multi-parameter respiration health monitoring. Cell Rep. Phys. Sci. 2023, 4, 101191.
  • 3.
    Xia, S.; Zhang, Q.; Song, S.; Duan, L.; Gao, G., Bioinspired dynamic cross-linking hydrogel sensors with skin-like strain and pressure sensing behaviors. Chem. Mater. 2019, 31, 9522–9531.
  • 4.
    Gong, J., Double-network hudrogels with extremely high mechanical strength. Adv. Mater. 2003, 15, 1155–1158.
  • 5.
    Wang, X.; Li, Z.; Wang, S.; Sano, K.; Sun, Z.; Shao, Z.; Takeishi, A.; Matsubara, S.; Okumura, D.; Sakai, N; et al. Mechanical nonreciprocity in a uniform composite material. Science 2023, 380, 192–198.
  • 6.
    Hu, L.; Chee, P.L.; Sugiarto, S.; Yu, Y.; Shi, C.; Yan, R.; Yao, Z.; Shi, X.; Zhi, J.; Kai, D.; et al. Hydrogel-based flexible electronics. Adv. Mater. 2023, 35, e2205326.
  • 7.
    Gao, Q.; Sun, F.; Li, Y.; Li, L.; Liu, M.; Wang, S.; Wang, Y.; Li, T.; Liu, L.; Feng, S.; et al. Biological tissue-inspired ultrasoft, ultrathin, and mechanically enhanced microfiber composite hydrogel for flexible bioelectronics. Nanomicro Lett. 2023, 15, 139.
  • 8.
    Bai, M.; Chen, Y.; Zhu, L.; Li, Y.; Ma, T.; Li, Y.; Qin, M.; Wang, W.; Cao, Y.; Xue, B., Bioinspired adaptive lipid-integrated bilayer coating for enhancing dynamic water retention in hydrogel-based flexible sensors. Nat. Commun. 2024, 15, 10569.
  • 9.
    Park, B.; Shin, J.H.; Ok, J.; Park, S.; Jung, W.; Jeong, C.; Choy, S.; Jo, Y.J.; Kim, T.-i., Cuticular pad–inspired selective frequency damper for nearly dynamic noise–free bioelectronics. Science 2022, 376, 624–629.
  • 10.
    Zhao, Z.; Liu, J.; Wu, M.; Yao, X.; Wang, H.; Liu, X.; He, Z.; Song, X., A soft, adhesive self-healing naked-eye strain/stress visualization patch. Adv. Mater. 2024, 36, e2307582.
  • 11.
    Li, W.; Zheng, S.; Zou, X.; Ren, Y.; Liu, Z.; Peng, W.; Wang, X.; Liu, D.; Shen, Z.; Hu, Y.; et al. Tough hydrogels with isotropic and unprecedented crack propagation resistance. Adv. Funct. Mater. 2022, 32, 2207348.
  • 12.
    Xie, Y.; Shi, X.; Gao, S.; Lai, C.; Lu, C.; Huang, Y.; Zhang, D.; Nie, S.; Xu, F.; Chu, F., Biomimicking natural wood to fabricate isotropically super-strong, tough, and transparent hydrogels for strain sensor and triboelectric nanogenerator applications. J. Mater. Chem. A 2024, 12, 5124–5132.
  • 13.
    Liu, M.; Ishida, Y.; Ebina, Y.; Sasaki, T.; Hikima, T.; Takata, M.; Aida, T., An anisotropic hydrogel with electrostatic repulsion between cofacially aligned nanosheets. Nature 2015, 517, 68–72.
  • 14.
    Mredha, M.T.I.; Guo, Y.Z.; Nonoyama, T.; Nakajima, T.; Kurokawa, T.; Gong, J.P., A facile method to fabricate anisotropic hydrogels with perfectly aligned hierarchical fibrous structures. Adv. Mater. 2018, 30, 1704937.
  • 15.
    Hiratani, T.; Kose, O.; Hamad, W.Y.; MacLachlan, M.J. Stable and sensitive stimuli-responsive anisotropic hydrogels for sensing ionic strength and pressure. Materals Horiz. 2018, 5, 1076–1081.
  • 16.
    Zhu, Q.L.; Du, C.; Dai, Y.; Daab, M.; Matejdes, M.; Breu, J.; Hong, W.; Zheng, Q.; Wu, Z.L. Light-steered locomotion of muscle-like hydrogel by self-coordinated shape change and friction modulation. Nat. Commun. 2020, 11, 5166.
  • 17.
    Liang, X.; Chen, G.; Lin, S.; Zhang, J.; Wang, L.; Zhang, P.; Wang, Z.; Wang, Z.; Lan, Y.; Ge, Q.; et al. Anisotropically fatigue-resistant hydrogels. Adv. Mater. 2021, 33, e2102011.
  • 18.
    Xue, P.; Bisoyi, H.K.; Chen, Y.; Zeng, H.; Yang, J.; Yang, X.; Lv, P.; Zhang, X.; Priimagi, A.; Wang, L.; et al. Near-infrared light-driven shape-morphing of programmable anisotropic hydrogels enabled by MXene nanosheets. Angew. Chem. Int. Eddition 2021, 60, 3390–3396.
  • 19.
    Sano, K.; Ishida, Y.; Aida, T., Synthesis of anisotropic hydrogels and their applications. Angew. Chem. Int. Ed. 2018, 57, 2532–2543.
  • 20.
    Uchida, N.; Ishida, Y., Macroscopically oriented polymeric soft materials: Synthesis and functions. 2019, 51, 709–719.
  • 21.
    Xiong, J.; Wu, W.; Hu, Y.; Guo, Z.; Wang, S., An anisotropic conductive hydrogel for strain sensing and breath detection. Appl. Mater. Today 2023, 34, 101909.
  • 22.
    Zhang, Y.; Fu, Z.; Wu, T.; Ren, B.; Chen, J.; Xie, F.; Leng, W.; Shi, J.; Lu, Y., Skin-inspired ultra-tough, self-healing anisotropic wood-based electronic skin for multidimensional sensing. Chem. Eng. J. 2024, 496, 154000.
  • 23.
    Teng, Y.; Zhang, Z.; Cui, Y.; Su, Z.; Godwin, M.; Chung, T.; Zhou, Y.; Leontowich, A.F.G.; Islam, M.S.; Tam, K.C.; et al. High-sensitivity and flexible motion sensing enabled by robust, self-healing wood-based anisotropic hydrogel composites. Small 2025, 21, 2500944.
  • 24.
    Geng, L.; Liu, W.; Fan, B.; Wu, J.; Shi, S.; Huang, A.; Hu, J.; Peng, X., Anisotropic double-network hydrogels integrated superior performance of strength, toughness and conductivity for flexible multi-functional sensors. Chem. Eng. J. 2023, 462, 142226.
  • 25.
    Chen, L.; Chang, X.; Chen, J.; Zhu, Y., Ultrastretchable, antifreezing, and high-performance strain sensor based on a muscle-inspired anisotropic conductive hydrogel for human motion monitoring and wireless transmission. ACS Appl. Mater. Interfaces 2022, 14, 43833–43843.
  • 26.
    Zhang, Y.; Jing, X.; Zou, J.; Feng, P.; Wang, G.; Zeng, J.; Lin, L.; Liu, Y.; Mi, H.; Nie, S., Mechanically robust and anti-swelling anisotropic conductive hydrogel with fluorescence for multifunctional sensing, Adv. Funct. Mater. 2024, 34, 2410698.
  • 27.
    Hang, C.; Guo, Z.; Li, K.; Yao, J.; Shi, H.; Ge, R.; Liang, J.; Quan, F.; Zhang, K.; Tian, X.; et al. Anisotropic hydrogel sensors with muscle-like structures based on high-absorbent alginate fibers. Carbohydr. Polym. 2025, 349, 123015.
  • 28.
    Wang, W.; Deng, X.; Luo, C., Anisotropic hydrogels with high-sensitivity and self-adhesion for wearable sensors. J. Mater. Chem. C 2023, 11, 196–203.
  • 29.
    Lin, H.; Wang, R.; Xu, S.; Li, X.; Song, S., Tendon-inspired anisotropic hydrogels with excellent mechanical properties for strain sensors. Langmuir 2023, 39, 6069–6077.
  • 30.
    Ghosh, A.; Pandit, S.; Kumar, S.; Pradhan, D.; Das, R.K., Human muscle inspired anisotropic and dynamic metal ion-coordinated mechanically robust, stretchable and swelling- resistant hydrogels for underwater motion sensing and flexible supercapacitor application. ACS Appl. Mater. Interfaces 2024, 16, 62743–62761.
  • 31.
    Huang, S.; Xiao, R.; Lin, S.; Wu, Z.; Lin, C.; Jang, G.; Hong, E.; Gupta, S.; Lu, F.; Chen, B.; et al. Anisotropic hydrogel microelectrodes for intraspinal neural recordings in vivo. Nat. Commun. 2025, 16, 1127.
  • 32.
    Lin, H.; Yuan, W.; Zhang, W.; Dai, R.; Zhang, T.; Li, Y.; Ma, S.; Song, S., Strong and tough anisotropic short-chain chitosan-based hydrogels with optimized sensing properties for flexible strain sensors. Carbohydr. Polym. 2025, 348, 122781.
  • 33.
    Fu, X.; Tong, H.; Zhang, X.; Zhang, K.; Douadji, L.; Kang, S.; Luo, J.; Pan, Z.; Lu, W., Anisotropic hydrogels with multiscale hierarchy based on ionic conductivity for flexible sensors. ACS Appl. Polym. Mater. 2023, 5, 9876–9887.
  • 34.
    Chen, S.; Guo, B.; Yu, J.; Yan, Z.; Liu, R.; Yu, C.; Zhaoa, Z.; Zhang, H.; Yao, F.; Li, J., A polypyrrole-dopamine/poly(vinyl alcohol) anisotropic hydrogel for strain sensor and bioelectrodes. Chem. Eng. J. 2024, 486, 150182.
  • 35.
    Shang, M.; Ma, S.; Ma, J.; Guo, L.; Liu, C.; Xu, X., Somatosensory actuators based on light-responsive anisotropic hydrogel for storage encryption of information systems. Chem. Eng. J. 2024, 496, 153895.
  • 36.
    Zhanga, X.; Langb, B.; Yu, W.; Jia, L.; Zhu, F.; Xue, Y.; Wu, X.; Qin, Y.; Chen, W.; Wang, Y.; et al. Magnetically induced anisotropic conductive hydrogels for multidimensional strain sensing and magnetothermal physiotherapy. Chem. Eng. J. 2023, 474, 145832.
  • 37.
    Chen, Z.; Wang, H.; Cao, Y.; Chen, Y.; Akkus, O.; Liu, H.; Cao, C., Bio-inspired anisotropic hydrogels and their applications in soft actuators and robots. Matter 2023, 6, 3803–3837.
  • 38.
    Sasaki, T.; Watanabe, M.; Hashizume, H.; Yamada, H.; Nakazawa, H. Macromolecule-like aspects for a colloidal suspension of an exfoliated titanate. Pairwise association of nanosheets and dynamic reassembling process initiated from it. J. Am. Chem. Soc. 1996, 118, 8329–8335.
  • 39.
    Tanaka, T.; Ebina, Y.; Takada, K.; Kurashima, K.; Sasaki, T., Oversized titania nanosheet crystallites derived from flux-grown layered titanate single crystals. Chem. Mater. 2003, 15, 3564–3568.
  • 40.
    Kim, Y.S.; Liu, M.; Ishida, Y.; Ebina, Y.; Osada, M.; Sasaki, T.; Hikima, T.; Takata, M.; Aida, T., Thermoresponsive actuation enabled by permittivity switching in an electrostatically anisotropic hydrogel. Nat. Mater. 2015, 14, 1002–1007.
  • 41.
    Sano, K.; Kim, Y.S.; Ishida, Y.; Ebina, Y.; Sasaki, T.; Hikima, H.; Aida, T. Photonic water dynamically responsive to external stimuli. Nat. Commun. 2016, 7, 12559.
  • 42.
    Sano, K.; Arazoe, Y.; Ishida, Y.; Ebina, Y.; Osada, M.; Sasaki, T.; Hikima, T.; Aida, T., Extra-large mechanical anisotropy of a hydrogel with maximized electrostatic repulsion. Angew. Chem. Int. Ed. 2018, 57, 12508–12513.
  • 43.
    Sun, Z.; Yamauchi, Y.; Araoka, F.; Kim, Y.S.; Bergueiro,J.; Ishida, Y.; Ebina, Y.; Sasaki, T.; Hikima, T.; Aida, T., An Anisotropic hydrogel actuator enabling earthworm-like directed peristaltic crawling. Angew. Chem. Int. Ed. 2018, 57, 15772–15776.
  • 44.
    Zhan, Y.; Ogawa, D.; Sano, K.; Wang, X.; Araoka, F.; Sakai, N.; Sasaki, T.; Ishida, Y., Reconfigurable photonic crystal reversibly exhibiting single and double structural colors. Angew. Chem. Int. Ed. 2023, 62, e202311451.
  • 45.
    Gabriel, J.-C. P.; Camerel, F.; Lemaire, B.J.; Desvaux, H.; Davidson, P.; Batail, P. Swollen liquid-crystalline lamellar phase based on extended solid-like sheets. Nature 2001, 413, 504–508.
  • 46.
    Hu, H.; Gopinadhan, M.; Osuji, C.O., Directed self-assembly of block copolymers: A tutorial review of strategies for enabling nanotechnology with soft matter. Soft Matter 2014, 10, 3867–3889.
  • 47.
    Osada, M.; Ebina, Y.; Fukuda, K.; Ono, K.; Takada, K.; Yamaura, K.; Takayama-Muromachi, E.; Sasaki, T., Ferromagnetism in two-dimensional Ti0.8Co0.2O2 nanosheets. Phys. Rev. B 2006, 73, 153301.
  • 48.
    Qu, M.; Xie, Z.; Liu, S.; Zhang, J.; Peng, S.; Li, Z.; Lin, C.; Nilsson, F., Electric resistance of elastic strain sensors—Fundamental mechanisms and experimental validation. Nanomaterials 2023, 13, 1813.
  • 49.
    Vázquez-Torres, N.A.; Benítez-Martínez, J.A.; Vélez-Cordero, J.R.; Sánchez-Arévalo, F.M., Experimental and numerical characterization of a flexible strain sensor based on polydimethylsiloxane polymeric network and MWCNT’s. J. Polym. Res. 2024, 31, 211.
Share this article:
Download PDF
Supplementary Materials
DOI
10.53941/mi.2025.100019
Issue
Volume 2, Issue 2
How to Cite
Xie, Y.; Wang, S.; Zhang, Y.; Kanai, H.; Yamada, K.; Wakamatsu, T.; Hamada, Y.; Obuse, S.; Zhang, D.; Chu, F.; Ishida, Y. An Anisotropic Hydrogel with Simple Preparation and Well-Defined Structure as a New Platform for Flexible Sensors with Directional Strain and Force Sensing. Materials and Interfaces 2025, 2 (2), 239–249. https://doi.org/10.53941/mi.2025.100019.
RIS
BibTex
Copyright & License
article copyright Image
Copyright (c) 2025 by the authors.