Local Shearing Force Measurement during Frictional Sliding Using Fluorogenic Mechanophores

Chao Chun Hsu, Feng Chun Hsia, Bart Weber, Matthijn B. de Rooij, Daniel Bonn, Albert M. Brouwer*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

7 Citations (Scopus)
41 Downloads (Pure)


When two macroscopic objects touch, the real contact typically consists of multiple surface asperities that are deformed under the pressure that holds the objects together. Application of a shear force makes the objects slide along each other, breaking the initial contacts. To investigate how the microscopic shear force at the asperity level evolves during the transition from static to dynamic friction, we apply a fluorogenic mechanophore to visualize and quantify the local interfacial shear force. When a contact is broken, the shear force is released and the molecules return to their dark state, allowing us to dynamically observe the evolution of the shear force at the sliding contacts. We find that the macroscopic coefficient of friction describes the microscopic friction well, and that slip propagates from the edge toward the center of the macroscopic contact area before sliding occurs. This allows for a local understanding of how surfaces start to slide.

Original languageEnglish
Pages (from-to)8840-8844
Number of pages5
JournalThe journal of physical chemistry letters
Issue number38
Publication statusPublished - 29 Sept 2022


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