Zhao Wenyu, Lin Zhuofan, Wang Xiaopu, Wang Ziya, Sun Zhenglong
School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen 518172, China.
Center for Stretchable Electronics and Nano Sensors, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
Gels. 2022 Sep 30;8(10):625. doi: 10.3390/gels8100625.
Hydrogels are stretchable ion conductors that can be used as strain sensors by transmitting strain-dependent electrical signals. However, hydrogels are susceptible to dehydration in the air, leading to a loss of flexibility and functions. Here, a simple and general strategy for encapsulating hydrogel with hydrophobic elastomer is proposed to realize excellent water-retention capacity. Elastomers, such as polydimethylsiloxanes (PDMS), whose hydrophobicity and dense crosslinking network can act as a barrier against water evaporation (lost 4.6 wt.% ± 0.57 in 24 h, 28 °C, and ≈30% humidity). To achieve strong adhesion between the hydrogel and elastomer, a porous structured thermoplastic polyurethane (TPU) is used at the hydrogel-elastomer interface to interlock the hydrogel and bond the elastomer simultaneously (the maximum interfacial toughness is over 1200 J/m). In addition, a PDMS encapsulated ionic hydrogel strain sensor is proposed, demonstrating an excellent water-retention ability, superior mechanical performance, highly linear sensitivity (gauge factor = 2.21, at 100% strain), and robust interface. Various human motions were monitored, proving the effectiveness and practicability of the hydrogel-elastomer hybrid.
水凝胶是可拉伸的离子导体，通过传输与应变相关的电信号可作为应变传感器。然而，水凝胶在空气中易脱水，导致失去柔韧性和功能。在此，提出了一种用疏水性弹性体封装水凝胶的简单通用策略，以实现优异的保水能力。弹性体，如聚二甲基硅氧烷（PDMS），其疏水性和致密的交联网络可作为防止水蒸发的屏障（在28°C、约30%湿度条件下24小时内失重4.6 wt.%±0.57）。为了实现水凝胶与弹性体之间的强粘附，在水凝胶-弹性体界面使用多孔结构的热塑性聚氨酯（TPU），以同时使水凝胶互锁并粘结弹性体（最大界面韧性超过1200 J/m）。此外，还提出了一种PDMS封装的离子水凝胶应变传感器，其具有优异的保水能力、卓越的机械性能、高度线性的灵敏度（应变100%时应变片系数=2.21）和坚固的界面。监测了各种人体运动，证明了水凝胶-弹性体复合材料的有效性和实用性。
