Silk Fibroin-Regulated Nanochannels for Flexible Hydrovoltaic Ion Sensing.

The evaporation-induced hydrovoltaic effect based on ion-selective nanochannels could theoretically be employed for high-performance ion sensing, yet the indeterminate ion-sensing properties and the acquisition of high sensing performance has rarely been explored. Herein, we present a controllable nanochannel regulation strategy for flexible hydrovoltaic devices with highly sensitive ion-sensing abilities across a wide concentration range. By multiple dip-coating silk fibroin on an electrospinning nylon-66 nanofiber film, the surface polarity enhancement, the fibers size regulation with a precision of approximately about 25 nm, and the nanostructure firm binding are achieved simultaneously. The resultant flexible freestanding hydrovoltaic device exhibits an open circuit voltage up to 4.82 V in deionized water, a wide ion sensing range of 10 -7 to 10 0  M and ultrahigh sensitivity as high as 1.37 V dec -1 , which is significantly higher than the sensitivity of the traditional solid-contact ion-selective electrodes. The fabricated flexible ion-sensitive hydrovoltaic device is successfully applied for wearable human sweat electrolyte sensing and for environmental trace-ion monitoring, thereby confirming the potential application of the hydrovoltaic effect for ion sensing. This article is protected by copyright. All rights reserved.