Displacement and strain mapping for osteocytes under fluid shear stress using digital holographic microscopy and digital image correlation

Osteocytes, as the mechano-sensors in bone, are always subjected to fluid shear stress (FSS) from the surrounding matrix. Quantification of FSS-induced cellular deformation is significant for clarifying the "perceive and transmit" process of cellular mechanotransduction. In this research, a label-free displacement and strain mapping method based on digital holographic microscopy (DHM) and digital image correlation (DIC) is introduced. The method, which is termed DHM-DIC, innovatively utilizes surface features extracted from holographic phase images instead of speckles as the metric for DIC searching. Simulation results on a hemisphere validate the feasibility of DHM-DIC. Displacement and strain maps of living osteocytes under 1.5 Pa FSS are evaluated from DHM-DIC and present good agreement with our previous finite element modeling results.