External Control of Liquid Nanofilms for Switchable Friction and Adhesion

Project Information

LIQUISWITCH

Grant agreement ID: 676861

DOI

10.3030/676861

Project closed

EC signature date 1 February 2016

Start date 1 April 2016

End date 30 September 2021

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 1 492 828,00

EU contribution

€ 1 492 828,00

Coordinated by

THE CHANCELLOR, MASTERS AND SCHOLARS OF THE UNIVERSITY OF OXFORD
United Kingdom

Periodic Reporting for period 4 - LIQUISWITCH (External Control of Liquid Nanofilms for Switchable Friction and Adhesion)

Reporting period: 2020-10-01 to 2021-09-30

Summary of the context and overall objectives of the project

Many of the natural and technological materials we encounter in life have important characteristics defined by their surface or interface. For example our sense of touch mostly relies on the mechanical characteristics of the surface of objects; and new technologies exploit interfaces such as the finely tuned electrical properties of the touch-screens on mobile devices. Surfaces and interfaces have been studied for many years, but less understood is the role of thin liquid films on solid materials or confined between two solid materials. These thin liquid films – which are ubiquitous in atmospheric conditions – can drastically alter the surface characteristics. From our common experience we know that dry sand runs freely whereas a small amount of water causes sand to hold its shape; and small amounts of oil are effective in lubricating mechanical parts. With this project the aim is to transform these well-known and ‘passive’ effects of thin liquid films into an ‘active’ technology for switching material properties. The work is fundamental in nature and aimed at understanding the underpinning concepts required to make this work: we are building delicate instruments to measure and characterise thin liquid films and to apply controlled electric fields across them. The results are anticipated to provide detailed understanding of the basic science required to control and switch surface interactions using external fields.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Our first objective was to build instruments capable of applying well-controlled electric fields across liquid films, and at the same time measure with high accuracy the thickness and other (optical, mechanical) properties of the liquid films. We have now succeeded in constructing several versions of this apparatus, and have published papers reporting the details of how it works so that other scientists could make similar measurements in future. Along the way, and while carrying out control experiments, we have discovered some unanticipated behaviours of the liquid films, particularly liquid containing high concentrations of ions (salt). We continue to investigate the detailed origins of the behaviour in order to better understand the properties of liquids.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

We have progressed beyond the state of the art in terms of the instruments built and reported (see publications in Review of Scientific Instruments between 2016-18), and the discovery of previously-unknown forces and screening of electric fields in highly concentrated electrolytes (publications from 2016-18 in J. Phys. Chem. Letters, Faraday Discussions, and Physical Review Letters).
The expected results by the end of the project include reports of switching liquid film properties using electric fields, and a full analysis of the field-screening properties in electrolytes.

Diagram of the adhesion switching apparatus and measurement