Controlled ion immigration in MXene-PVA composites for self-powered pressure sensor

Demanded by the increasing popularity of human–machine interface, wearable electronics, robots, etc., the current mainstream pressure sensing technologies could not fully fulfill the accurate and in-time sensing requirement. Ionic-based pressure sensors, which are inspired by the working mechanism of human haptic system, present several outstanding advantages and great potential. However, how to effectively control the ion transport and compensation under mechanical deformation in ionic-devices serves as a critical challenge in this new and under-developed field. In this study, we designed and constructed an ion-selective membrane based on 2D MXene to modulating the directional cations immigration in PVA hydrogels, which is the first demonstration in this field. To be specifically, the cations are trapped by the cation-selective MXene membrane due to the negative charge surface of MXene, which creating the ion concentration gradient within the PVA hydrogels and in turn the maximum power output up to 3.81 μW/cm 2 . On this basis, we prepare a concentration difference cell by placing the MXene film between two PVA hydrogels with different ionic concentration. Furthermore, the MXene film was placed between two PVA hydrogels with different moduli and the ion transport could be induced by the stress-induced inhomogeneous deformation, resulting in the formation of ionic concentration differential. Above two models were packed as the arrays to create an ionic touchpad, which is capable of detecting and differentiating various external stimuli accurately. This work explores two kinds of transport models by designing the layer arrangement of PVA hydrogels and MXene membrane, which provides a simple and versatile strategy for developing ionic-based self-powered pressure sensors.