Molecular-Scale Geometry Switching for Proton-Driven Macroscopic Actuation

Abstract

A conceptual framework for mechanical actuation is presented, rooted in molecular-level structural switching via ligand isomerization around a central metal ion. During the α to β ligand geometric switching, intramolecular hydrogen bonding, a key attractive interaction, is dismantled, dramatically enhancing proton charge localization and its spatial organization. This structural realignment in the β isomer results in a threefold increase in anion population at the electric double layer, unleashing a fundamentally unique proton-driven mechanical response. Unlike conventional methods, this mechanism offers an unexplored dimension, translating precise molecular reconfigurations into macroscopic motion. This work highlights how molecular-level structural switching can serve as a design principle for creating highly responsive, adaptable soft actuators, paving the way for advances in soft robotics, molecular machinery, and dynamic materials.