Influence of adhesion on oscillatory indentations of viscoelastic biomaterials by a rigid cone

Steady-state responses in oscillatory indentation tests are widely adopted to evaluate the viscoelastic behavior of cells and tissues. In such tests, the adhesion of biomaterials is commonly neglected, which leads to significant inaccuracy in extracting the mechanical properties. In this article, by introducing the interfacial adhesion described by Lennard-Jones potential, we develop a finite element method to simulate the oscillatory indentation on a viscoelastic half-space. Under a sinusoidal displacement excitation by a rigid cone, it is found that the reaction force evolves sinusoidally at the same frequency but having some phase shift. Interfacial adhesion magnifies the amplitude of force vibration while lowers the average repulsive force. The phase shift is eased in the case of weak adhesion, but turns aggravated once the strength of adhesion exceeds a critical value. The present study can provide guidance for the development of oscillatory indentation tests on viscoelastic materials, and extract more precisely their mechanical properties.