Ion transport-triggered rapid flexible hydrovoltaic sensing
Changlei Ge, Mingxu Wang, Yuchen Zhou, Yongfeng Wang, Feijun Zhao, Cunkai Zhou, Jun Ma, Feng Wen, Shuqi Wang, Mengyuan Liu, Shuanglan Wang, Yujie Liu, Hao Shen, Fuqin Sun, Lian-Hui Li, Ting Zhang
Abstract
The hydrovoltaic effect, based on interactions at the solid-liquid interface, offers a promising route for ion sensing. However, it is hampered by long response times, typically several minutes, due to slow ion diffusion equilibrium in nanochannels. Here, we demonstrate a rapid, flexible hydrovoltaic ion sensing strategy enabled by fast ion transport. Apart from the drag resistance reduction resulting from the ordered nanochannels and gravity elimination along the nanochannel direction, the liquid-driven effect concurrent with low-resistance shear flow at the liquid-liquid transport zone in semi-dry nanochannels are proposed to achieve an open-circuit voltage exceeding 4.0 V within 0.17 s, being two orders of magnitude faster than previous works with infiltration channels. Moreover, the obtained flexible hydrovoltaic device exhibits a wide ion sensing range of 10−7 to 100 M, a maximum sensitivity up to −1.69 V dec-1 for NaCl, and distinctive multi-dimensional signals, enabling its application in selective ion sensing and sweat electrolyte monitoring. The hydrovoltaic effect offers a promising route for ion sensing but is limited by a long response time. Here, the authors leverage rapid ion transport within nanochannels to achieve a high voltage output of 4.0 V with a response time of just 0.17 s.