Friction in quantitative micro-elastography

Quantitative micro-elastography (QME), an emerging compression optical coherence elastography technique, is used to measure the mechanical properties of tissue on the microscale. As QME requires contact between the loading plate and the sample, knowledge of the boundary conditions at the contact surface, including friction, is required to accurately calculate elasticity. In previous implementations of QME, a lubricant is applied at the contact surfaces, and it is assumed that this results in negligible friction. In this work, for the first time, we demonstrate that experimental factors including the application method and viscosity of the lubricant, as well as the mechanical contrast between the compliant layer and the sample affect friction and, therefore, the accuracy of QME. For instance, in the absence of appropriate lubrication, errors as large as 92% were observed, while the development of an optimised lubrication protocol provided accurate elasticity measurements for a wide range of samples elasticity (from 3 kPa to 130 kPa) to within 10% error.