E. Abbá; D. Axinte; A. Speidel; Z. Liao
Materials Today 86 (2025) 183–201
Active interactions at liquid-to-solid interfaces can significantly impact the mechanical response of
solid substrates. Traditionally, these have been regulated through surface-active media, such as ionic
liquids, used in a static (time-invariant) manner that relies on chemical tuning to induce specific
mechanochemical responses. This study introduces a novel and sustainable class of Deep Eutectic
Solvents (DESs) to demonstrate a dynamic (time-variant) mechanochemical effect, achieved through
molecular electro-actuation at the fluid-to-solid interface. The dynamic micro-mechanochemical effect
was demonstrated using a DES mixture consisting of citric acid and choline chloride in a 1:1 M ratio,
applied to a nickel single-crystal micro-cantilever substrate. The findings show how the DES coating
alone induced compressive surface stress, resulting in a 34 % increase in principal stress. More notably,
when the substrate surface was polarized with a ±5 V potential, electro-actuation amplified this
mechanochemical effect by up to 51 %, confirming a clear dynamic response. Further validation was
presented at the macroscale in a polycrystalline material setting, where a similar response was
observed. These findings give insight into the possible development of smart surfaces coated with DESs,
where a single chemical system can dynamically alter materials’ mechanical response through simple
electro-actuation, offering versatile applications across micro and macro scales.