Viscoelastic recovery times of chondrocytes measured using a novel 3D-printed microfluidic device

This paper presents the development, production, and application of a 3D-printed microfluidic device designed to measure the viscoelastic recovery time of cartilage cells, chondrocytes. Bovine chondrocytes were imaged using a confocal microscope while compressed by a movable glass plate. Their recovery was monitored by tracking their projected area over time, converting it into a linear strain, and fitting it to a Burgers mechanical model. Strains ranging from 10% to 60% were applied to the cells, and model parameters, including the viscoelastic recovery time, were derived. We found that cells subjected to strains greater than 40% exhibited radially-symmetric deformations. This radially-symmetric deformation, possibly cell blebbing, was observed as a short-term effect, with the cell fully recovering its initial shape. Non-blebbing and blebbing chondrocytes exhibited viscoelastic recovery times of 42 s and 38 s, respectively. While the recovery time did not depend on the magnitude of applied strain, the measured permanent strain increased with higher applied strain magnitude. Overall, this study demonstrates the use of a new, low-cost 3D-printed microfluidic device in combination with advanced microscopy for characterizing the viscoelastic properties of cells.