Gold-based platform enables direct visualization of nanoscale binding forces

Gold-based platform enables direct visualization of nanoscale binding forces
by Robert Schreiber
Berlin, Germany (SPX) Oct 24, 2025

Researchers at Chalmers University of Technology in Sweden have introduced an efficient method for examining the forces that hold together the smallest objects in nature. Their technique, which employs gold flakes suspended in salt water and illuminated with light, forms a visualized platform for investigating nature's invisible glue. Using two thin glass plates and gold-coated surfaces, the experimental setup enables scientists to observe these forces as distinct colors reflected by the self-assembled cavities between the flakes and the substrate.

The research team, led by doctoral student Michaela Hoskova, demonstrated that gold flakes introduced to a salt solution naturally gravitate towards a gold-coated substrate but leave nanometric spaces between the flakes and the surface. These cavities act as light resonators, producing visible color changes under a microscope equipped with a spectrometer. As observed on connected monitors, the nanoparticles continuously move and change color in real time.

Through trapped light within these cavities, the team precisely measures the balance of opposing forces at play, the Casimir effect, which pulls gold flakes together and to the surface, and electrostatic forces in the solution, which keep them apart. When the forces reach equilibrium, a self-assembly process results in the formation of nanoscale cavities, unlocking new opportunities for understanding nanoscale interactions. "What we are seeing is how fundamental forces in nature interact with each other. Through these tiny cavities, we can now measure and study the forces we call 'nature's glue' - what binds objects together at the smallest scales. We don't need to intervene in what is happening, we just observe the natural movements of the flakes," said Michaela Hoskova.

This platform is an evolution of years of work by Professor Timur Shegai's research group at Chalmers. From their foundational discovery that gold flakes self-assemble into resonators, the group has refined a way to probe particle-level interactions. According to Shegai, "The method allows us to study the charge of individual particles and the forces acting between them. Other methods for studying these forces often require sophisticated instruments which cannot provide information down to the particle level."

The development opens avenues across physics, chemistry, material science, and technology, with implications for understanding interactions in liquids, drug delivery pathways, biosensor construction, water filters, and the stability of consumer products. Hoskova emphasizes the accessibility of the approach, noting, "What I find most exciting is that the measurement itself is so beautiful and easy. The method is simple and fast, based only on the movement of gold flakes and the interaction between light and matter."

The experimental system consists of approximately 10 micrometre gold flakes placed in saltwater, deposited onto a gold-coated substrate. Nanometric cavities form as self-assembly driven by the Casimir force and electrostatic repulsion. Using a halogen lamp and an optical microscope with spectrometry, scientists can analyze the distance-dependent effects by adjusting salinity and recording color variations. All elements required for analysis are enclosed between two glass plates.

Research Report:Casimir self-assembly: A platform for measuring nanoscale surface interactions in liquids