Engineering a Mechanical Stimulation System for Inducing Shear Stress in Chondrocyte Cultures

This paper presents the development of a mechanical stimulation system designed for chondrocyte cell culture, specifically aimed at applying controlled shear stress to chondrocyte cells grown on a 12-well plate. Understanding the impact of shear stress on chondrocytes requires careful observation of the regulation of key proteins, including collagen type I, collagen type II, and aggrecan. The stimulation system is engineered to deliver intermittent fluid shear stress within the range of 0.3--1 Pa, which is achieved through the movement of a piezoelectric stack actuator. The system accommodates a 12-well cell culture plate and features a 12-probe fluid shear stirrer that operates at a frequency of 30 Hz. During operation, the stirrer exerts pressure on the culture media, inducing oscillatory motion that generates fluid shear stress. To evaluate the performance of the mechanical stimulation system, we experimentally varied the probe displacement at increments of 2.91, 16.19, 28.31, 39.56, and 42.43 µm. The corresponding velocities were measured at 178.6, 1495, 2515, 3741, and 4821 µm/s. These observed displacement and velocity values were then theoretically converted to shear stress, confirming that the generated shear stress falls within the desired magnitude of 0.045 to 1.218 Pa. Thus, the system is capable of effectively producing the necessary fluid shear stress for chondrocyte studies.