Accurate and real-time monitoring of electrophysiological signals is essential to improve the quality of human life and productivity. Bioelectrodes are an important tool for recording electrophysiological signals and an important communication route between humans and external devices. As a result, they place high demands on the histocompatibility, seamless fit, conductivity, and biocompatibility of interfacial materials.
Despite great efforts in the development of bioelectrodes, they are still not immune to the effects of the aqueous environment, which reduces adhesion and increases the interfacial impedance, thus reducing the performance of bioelectrodes. In addition, the integration of bioelectrodes into clothing as smearable electrodes remains a significant challenge for capturing electrophysiological signals in a wearable, senseless, and seamless manner.
Therefore, it is imperative to: (1) develop a bioelectrode that is both waterproof and maintains stable adhesion, electrical, and mechanical properties in an aqueous environment, and that the bioelectrode should also be adaptable to clothing and skin shape for wearable electrophysiological signal detection, and (2) understand the role of new mechanisms in waterproof bioelectrodes.
Recently, the research team of Zhang Qinghong and Hou Chengyi of Donghua University published an article entitled "On-Skin Paintable Water-Resistant Biohydrogel for Wearable Bioelectronics" in Advanced Functional Materials. The study proposes a skin-appliable, waterproof biohydrogel that achieves water resistance through water-initiated hydrogen bond densification (Figure 1). This hydrogel breaks the morphological limitations of existing bioelectric electrodes by using dynamic hydrogen bonding, and by using ethanol to dynamically modulate the hydrogen bonding network between polyvinyl alcohol and tannins, the prepolymer solution of the hydrogel can be transformed into a hydrogel film in less than two minutes and form a seamless interface with skin and clothing.
Figure 1: A skin-definable waterproof biohydrogel
Dense hydrogen bonding is responsible for increased water resistance and adhesion. When this hydrogel is in an aqueous environment, the free tannic acid is induced to form a denser hydrogen bond network with polyvinyl alcohol, resulting in a waterproof layer. In addition, the tighter hydrogen bond structure increases the energy expenditure during peeling, resulting in improved adhesion properties. The densified hydrogen bonding network also enhances the Grotthuss mechanism, thereby enhancing the conductivity of the hydrogel in the aqueous environment. This method is expected to be universally applicable for the production of waterproof bioelectrical electrodes (see Figure 2).
Fig.2 Waterproofing, viscosity, and conductivity enhancement mechanisms triggered by water
Based on the hydrogel, the team has also developed a wearable, multi-channel bioelectrode method that can be applied directly to clothing. The use of this hydrogel can improve the signal-to-noise ratio by 83.5% compared to existing medical methods (see Figure 3).
Fig.3 Wearable multi-channel biopotential monitoring application based on this hydrogel
Luo Jiabei and Sun Chuanyue, doctoral students of Donghua University, are the co-first authors of the paper, and Zhang Qinghong and Hou Chengyi, researchers of Donghua University, are the corresponding authors. The research was supported by the Outstanding Young Professor Program of Donghua University, the Special Fund for Fundamental Research of the Central Universities, and the Graduate Innovation Fund of Donghua University.
近年来，东华大学张青红、侯成义研究员在健康监测纤维织物、钙钛矿太阳能电池、光电子纤维器件、皮肤界面材料等领域取得了系列进展（Science 2024, 384,74. Science, 2022, 377, 815 (perspective). Science Advances, 2024, 10, eadk4620. Nature Communications, 2024, 15, 2374. Nature Communications, 2019, 10, 5541. Nature Communications, 2019, 10, 868. Advanced Materials, 2024, 36, 202310102. Advanced Materials, 2021, 33, 2104681. Advanced Materials, 2021, 33, 2100782. Advanced Materials, 2021, 33, 2007352. Advanced Energy Materials, 2024,14, 2303666. ACS Nano 2024, 18, 5, 4008. ACS Nano, 2022, 16, 19373. ACS Nano, 2022, 16, 12635. ACS Nano, 2022, 16, 2188.），长期欢迎材料、信息、纺织、服装等专业的博士后、博士研究生、硕士研究生加入！https://onlinelibrary.wiley.com/doi/full/10.1002/adfm.202400884来源：本文系作者授权，独家发布。