Friction Memory Ionogels With Hysteretic Sticky‐Slippery Transition via Thermolocking the Metastable state

Abstract

Many biological organisms possess adaptive friction states and display hysteretic friction recovery, allowing them to achieve specific friction memory after environment change. However, current artificial materials have limitations in maintaining on-demand friction states upon withdrawal of external triggers due to their strong dependence on external stimulus. Here, thermally induced phase separation ionogels with friction memory are reported. The kinetic difference between the evolution of bulk condensed structure and the adsorption of surface droplets after removing external stimulus delayed the recovery of friction state transition from slippery to sticky, thus achieving responsive friction memory. In addition, the metastable intermediate state generated during phase separation could be locked through vitrification, resulting in three distinct friction states determined by the synergy of stiffness and surface properties, including sticky state (coefficient of friction of 1.8), medium state (0.3-0.5) and slippery state (0.03-0.07). As a proof-of-concept, smart devices with diverse surface friction performance are engineered to realize various functions, including recognition of thermal range for target objects, de-icing, and movement manipulation. These results provide new insights for expanding the applications of ionogels in state-of-the-art soft robotics and haptic engineering, offering fresh perspectives for further development of these fields.