Side-View Imaging-Based Analysis of the Balloon Inflation–Deflation Dynamics of a Microfluidic Cell Compressor

Abstract

Microfluidic devices are utilized to mechanically stimulate cells for cellular mechanobiology studies. Previously, we developed a microfluidic cell compressor using photolithography and soft lithography. The device had thin polydimethylsiloxane (PDMS) balloons that would bulge under applied pressure and compress cells in hydrogel placed on the balloons. Since the height of the inflated balloons played a key role in the amount of compression that cells experienced, understanding the inflation dynamics of the balloon is key to assessing the performance of the cell compression device. In this study, we have improved the fabrication method of the microfluidic cell compressor by printing a master mold using a commercial microfluidic 3D printer for more cost-effective fabrication with higher design flexibility. While the balloon was dynamically actuated with various pressures and frequencies, its inflation and deflation cycles were imaged in side-view using high-speed videography. We found that the balloon inflated slowly, paused at its full inflation, and then deflated quickly responding to an applied square wave of pressure, and that the maximum balloon height increased with the applied pressure, while it decreased with the actuation frequency. As the inflation frequency increased, inflation speed also increased but became less stable. At lower frequencies, the behavior of the balloon was more stable and predictable. The method and result of this study lend us insight on how to improve the design and operating condition of the microfluidic cell compressor and similar PDMS-membrane-based microfluidic devices.