There is an urgent need to develop self-powered technologies for portable strain/pressure sensors. In this work, inspired by salinity-gradient electricity generation, we report the design and fabrication of a mechanical-electric conversion and self-powered sensing platform based on polyelectrolyte hydrogels. Using polyacrylic acid (PAA, whose -COOH group can ionize H⁺ in water) hydrogel as a model system, we observe that the compression deformation process of the hydrogel leads to a localized increase in the H⁺ concentration, that induces a directional H⁺ diffusion as a result of ion concentration difference. In contrast, the PAA chain (negatively charged), as a hydrogel backbone, is hindered from moving freely due to the locking of the hydrogel network. Such drastic difference between ionized H⁺ and fixed PAA chain defines an opportunity for converting mechanical energy into electricity by compressing the PAA hydrogel. The good elasticity of the PAA hydrogel allows us to repeatedly regenerate and fully recover the electrical signal and finally completes the recycle sensing (>1000 s). PAA hydrogels have also been shown to convert static or low frequency (∼0.05 Hz) pressure (0.05–5 N) to output direct voltage/current. In particular, the hydrogel can yield a voltage output up to ∼6 mV and a current of ∼2 μA when the pressure is 5 N. Taking full advantage of the special sensing principle, we have developed both self-powered and temperature-insensitive PAA hydrogel-based position recognizers and multi-dimensional sound detectors. Importantly, this mechanical-to-electric conversion concept is also applicable to other polyelectrolyte hydrogels. This simple and low-cost soft material system is promising for applications in sensing and energy harvesting.

迫切需要开发用于便携式应变/压力传感器的自供电技术。在这项工作中，受盐度梯度发电的启发，我们报告了基于聚电解质水凝胶的机电转换和自供电传感平台的设计和制造。使用聚丙烯酸（PAA，其 -COOH 基团可以电离水中的 H ⁺）水凝胶作为模型系统，我们观察到水凝胶的压缩变形过程导致 H ⁺浓度的局部增加，从而导致定向 H ⁺离子浓度差的结果。相比之下，作为水凝胶骨架的 PAA 链（带负电）由于水凝胶网络的锁定而无法自由移动。电离 H ^{+之间的巨大差异}固定的 PAA 链定义了通过压缩 PAA 水凝胶将机械能转化为电能的机会。PAA水凝胶良好的弹性使我们能够反复再生并完全恢复电信号，最终完成循环感应（>1000 s）。PAA 水凝胶也被证明可以将静态或低频（~0.05 Hz）压力（0.05-5 N）转换为输出直流电压/电流。特别是，当压力为 5 N 时，水凝胶可以产生高达 ∼6 mV 的电压输出和 ∼2 μA 的电流。充分利用特殊的传感原理，我们开发了自供电和温度不敏感的 PAA基于水凝胶的位置识别器和多维声音检测器。重要的，这种机电转换概念也适用于其他聚电解质水凝胶。这种简单且低成本的软材料系统有望用于传感和能量收集。