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. 2022 May 12;65(9):2540–2552. doi: 10.1007/s40843-021-2022-1

Ultrasensitive, stretchable, and transparent humidity sensor based on ion-conductive double-network hydrogel thin films

基于离子导电双网络水凝胶薄膜的超灵敏、可拉 伸、透明湿度传感器

Zixuan Wu 1,#, Qiongling Ding 1,#, Zhenyi Li 1,#, Zijing Zhou 1, Luqi Luo 1, Kai Tao 2, Xi Xie 1, Jin Wu 1,✉
PMCID: PMC9109751  PMID: 35600911

Abstract

Ion-conductive hydrogels with intrinsic biocompatibility, stretchability, and stimuli-responsive capability have attracted considerable attention because of their extensive application potential in wearable sensing devices. The miniaturization and integration of hydrogel-based devices are currently expected to achieve breakthroughs in device performance and promote their practical application. However, currently, hydrogel film is rarely reported because it can be easily wrinkled, torn, and dehydrated, which severely hinders its development in microelectronics. Herein, thin, stretchable, and transparent ion-conductive double-network hydrogel films with controllable thickness are integrated with stretchable elastomer substrates, which show good environmental stability and ultrahigh sensitivity to humidity (78,785.5%/% relative humidity (RH)). Benefiting from the ultrahigh surface-area-to-volume ratio, abundant active sites, and short diffusion distance, the hydrogel film humidity sensor exhibits 2 × 105 times increased response to 98% RH, as well as 5.9 and 7.6 times accelerated response and recovery speeds compared with the bulk counterpart, indicating its remarkable thickness-dependent humidity-sensing properties. The humidity-sensing mechanism reveals that the adsorption of water improves the ion migration and dielectric constant, as well as establishes the electrical double layer. Furthermore, the noncontact human-machine interaction and real-time respiratory frequency detection are enabled by the sensors. This work provides an innovative strategy to achieve further breakthroughs in device performance and promote the development of hydrogel-based miniaturized and integrated electronics. graphic file with name 40843_2021_2022_Fig1_HTML.jpg

Electronic Supplementary Material

Supplementary material is available in the online version of this article at 10.1007/s40843-021-2022-1.

Keywords: stretchable hydrogel, humidity sensor, thin-film, ultrasensitive, wearable application

Supplementary Information

40843_2021_2022_MOESM1_ESM.pdf (1.3MB, pdf)

Ultrasensitive, stretchable, and transparent humidity sensor based on ion-conductive double-network hydrogel thin films

Acknowledgements

This work was supported by the National Natural Science Foundation of China (61801525), Guangdong Basic and Applied Basic Research Foundation (2020A1515010693), the Science and Technology Program of Guangzhou (201904010456), and the Fundamental Research Funds for the Central Universities, Sun Yat-sen University (22lgqb17).

Author contributions

Wu J, Wu Z, Ding Q, and Li Z designed the sensors, analyzed the results, and wrote the paper; Wu Z drafted the manuscript; Zhou Z, Luo L, Tao K, and Xie X contributed to the discussion of the results; Wu J revised the paper and supervised the project. All authors contributed to the general discussion.

Footnotes

Jin Wu received his PhD degree from Nanyang Technological University in 2014. After obtaining his PhD degree in 2014, he continued working in the SMART program at Nanyang Technological University as a postdoctoral research fellow. Since 2017, he has been an associate professor at the School of Electronics and Information Technology, Sun Yat-sen University. His research interest includes hydrogel-based sensors, and flexible and stretchable electronics.

Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary information

Supporting data are available in the online version of the paper.

These authors contributed equally to this work.

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Supplementary Materials

40843_2021_2022_MOESM1_ESM.pdf (1.3MB, pdf)

Ultrasensitive, stretchable, and transparent humidity sensor based on ion-conductive double-network hydrogel thin films

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