Hierarchical self-healing liquid metal architectures driven by electro-chemical synergy for ultrasensitive strain sensing

Abstract

Hierarchical-structured liquid metal (LM) has attracted considerable attention in fields of wearable electronics, soft robots and advanced catalysis. Although much progress has been made, it is still challenging to achieve controllable micro/nano hierarchical-structured LM with self-healing properties. Herein, inspired by the preparation method of the traditional Chinese foods “cold shrimp” and “vermicelli”, we demonstrate a strategy to achieve controllable and self-healing micro/nano hierarchical-structured LM based on electro-chemical synergy. When a voltage higher than the electrowetting threshold voltage is applied, LM will wet and spread out on the porous mesh surface owing to the formation of the oxide layer, and then permeate in the form of microstructured sphere-like, sphere-silk-like and silk-like LM under electrocapillary pressure and gravity in NaOH solution. To further solve the problem of hierarchical-structured LM agglomeration owing to Rayleigh-Plateau instabilities driven by surface tension, the Cu shell on the surface of hierarchical-structured LM is introduced as robust “armour” layer, which can maintain the morphology in acidic CuSO₄ solution with the concentration exceeding 6 wt%. Furthermore, the controllable, flexible, hierarchical-structured LM demonstrates exceptional self-healing capabilities in acidic CuSO₄ solution. Additionally, a strain sensor has been devised and constructed for monitoring human motion, utilizing the unique properties of the hierarchical-structured LM. Thus, this work provides an effective method to achieve controllable and self-healing hierarchical-structured LM, and providing new perspectives and insights to the fields of wearable electronics and soft robots.