# Electrically Switchable Molecular Adhesion via Self-Assembled Monolayer-Mediated Hydration and Ion Structuring

## TL;DR

This paper introduces a new method to control surface adhesion using electrical signals by manipulating ion and water structures at interfaces.

## Contribution

A novel electromechanical adhesion switch mechanism is demonstrated using surface modification and potential modulation.

## Key findings

- Molecular surface modifications significantly affect adhesive and repulsive forces between surfaces.
- Ion ordering under electrochemical modulation impacts film–mica interactions.
- Electromechanical adhesion switches can be tailored via ion adsorption manipulation.

## Abstract

The interplay of specific surface interactions as well
as ion and
hydration structuring takes on a pivotal role in dictating the intermolecular,
intersurface, and colloidal behavior at solid–liquid interfaces.
The detailed atomic and molecular structure consequently influences
a wide array of surface-mediated functions in technological and biological
systems. Ion and hydration structuring at the interface is susceptible
to various surface parameters, including surface potential, structural
modifications including molecular adsorbents, the charge of specific
functional groups, and electrolyte composition. Here, we disclose
an electromechanical adhesion switch mechanism and demonstrate, in
operation, the impact of molecular surface modification and potential
modulation on adhesive and repulsive forces between surfaces. We exemplify
these fundamental interactions by measuring the acting intermolecular
forces between mica and metal surfaces modified with self-assembled
monolayers including mercaptobenzimidazole and cysteamine films, showcasing
the potential for tailoring surface interactions via ion adsorption
manipulation. Employing an electrochemical surface forces apparatus
complemented with molecular dynamics simulation, we present a comprehensive
analysis of the specific forces involved in film–mica interactions
and the impact of ion ordering under electrochemical modulation on
such forces. Our results offer a novel perspective on how hydration
and ion adsorption shape solid–solid interactions involving
organic thin films and how these interactions provide a flexible route
for electromechanical adhesion switches.