Force measurement reveals structure of a confined liquid: Observation of the impenetrable space

Abstract Understanding of the structure of a confined liquid is an important subject for developments in surface science, tribology, biophysics, etc. In this study, we propose its measurement theory and conduct a test of the theory. The measurement theory uses a force curve obtained by surface force apparatus and transforms the force curve into the confined liquid structure. To check the validity of the measurement theory, we perform a verification test in a computer. It is found that the theory can semi-quantitatively reproduce the confined liquid structure. The theory will lead to the first step toward measuring a liquid structure confined between optically impenetrable substrates.