Recent Development of Self-Powered Tactile Sensors Based on Ionic Hydrogels.

Hydrogels are three-dimensional polymer networks with excellent flexibility. In recent years, ionic hydrogels have attracted extensive attention in the development of tactile sensors owing to their unique properties, such as ionic conductivity and mechanical properties. These features enable ionic hydrogel-based tactile sensors with exceptional performance in detecting human body movement and identifying external stimuli. Currently, there is a pressing demand for the development of self-powered tactile sensors that integrate ionic conductors and portable power sources into a single device for practical applications. In this paper, we introduce the basic properties of ionic hydrogels and highlight their application in self-powered sensors working in triboelectric, piezoionic, ionic diode, battery, and thermoelectric modes. We also summarize the current difficulty and prospect the future development of ionic hydrogel self-powered sensors.

1-[6-(3,5-Di-methyl-pyrazol-1-yl)-1,2,4,5-tetra-zin-3-yl]guanidin-2-ium perchlorate methanol monosolvate.

In the title solvated salt, C8H12N9 (+)·ClO4 (-)·CH3OH, the dihedral angle between the tetra-zine and pyrazole rings is 26.05 (7)°. The two N atoms bonded to the 1,2,4,5-tetra-zine ring deviate from the plane defined by its four N atoms by 0.234 (2) and 0.186 (2) Å. There is an intra-molecular N-H⋯N hydrogen bond between the protonated guanidine fragment and one of the tetra-zine N atoms. In the crystal, two cations and two perchlorate anions are connected via N-H⋯O hydrogen bonds into centrosymmetric assemblies. These assemblies are further linked into a two-dimensional network parallel to (100) via bifurcated O-H⋯(N,N) hydrogen bonds formed with the bridging methanol mol-ecules.