Comparative investigation into flexible alginate-based hydrogel sponges with excellent biocompatibility and breathability for reliable strain and pressure sensors.

Flexible sensors with a porous hydrogel structure have attracted enormous attention for their extensive potential prospects in the fields of wearable electronics and human-machine interaction (HMI). Nevertheless, these sensors encounter significant challenges in synchronously achieving breathability, favorable biocompatibility, and high strain/pressure sensitivity. Herein, various sodium alginate (SA)-based hydrogel sponges are prepared by a facile one-pot and directional freezing process for comparative studies. The obvious oriented and uniform pore structures can provide a spatial anisotropy dispersion framework for the conductive fillers, and the effective connectivity among these interface structures facilitates the rapid deformation and recovery of the entire structure. Compared to other hydrogel sponges, the SA/silk fibroin (SF) hydrogel sponge demonstrates a more consistent pore distribution, preferable size uniformity, mechanical strength, deformation capability, and porosity properties. The designed SA/SF-based strain sensor with a satisfied gauge factor of 1.69 and durability can precisely monitor the physiological signals produced by humans. It exhibits favorable pressure sensitivity (- 1.10 kPa