- The full article entitled “Electrically Switchable Molecular Adhesion via Self-Assembled Monolayer-Mediated Hydration and Ion Structuring” can be found at the JACS website at https://doi.org/10.1021/jacs.5c11903
- Authors: Valentina Wieser*, Yoyo Cheng-Ting Yu, Andrea Valencia Ramirez, David T. Wu, Frank Uwe Renner*, Hsiu-Wei Cheng*
Molecular adhesion plays a central role across diverse fields, from corrosion science and bio-lubrication to polymer research, arising from a complex balance of van der Waals, hydration, and electrostatic interactions. While self-assembled monolayers (SAMs) have long been used to tailor surface interactions through specific chemical or electrostatic mechanisms, the influence of the surrounding ionic environment remains less understood. In aqueous electrolytes, ions within the electric double layer (EDL) regulate surface charge and mediate how two surfaces actually “feel” each other across nanometer-scale gaps.
In this study, research team of Prof. Hsiu-Wei Cheng from NTU and Prof. David Wu from Sinica Academia combine an electrochemical Surface Forces Apparatus (SFA) with state-of-the-art Molecular Dynamics Simulations to directly probe how ion and hydration structuring at the interface governs adhesion between a benzimidazole-functionalized gold electrode and a mica surface. Force-Distance measurements and ion density profiles reveal a particular cation-trapping mechanism that stabilizes hydration layers at low surface potentials, producing strong repulsive forces. By tuning the surface potential, these hydration and ion structures can be reversibly reorganized, effectively creating an electrically switchable adhesion system controlled by EDL and molecular-scale structuring.
This work provides new mechanistic insight into electrochemically tunable adhesion and opens pathways toward molecularly engineered interfaces for adaptive and responsive materials.