An open-source, battery-powered, low-cost, and dual-channel pneumatic pulse generator for microfluidic cell-stretch assays

Cells in the body are regularly subjected to mechanical forces that influence their biological fate in terms of morphology, gene expression, and differentiation. The current gold standard method to replicate these effects in vitro is to culture cells on devices with elastic substrates and to impart mechanical stretch using mechanical or pneumatic pull-push methods. Microfluidic device designs offer several advantages in this context for general uniform and controlled stretching. However, the experimental setups are bulky, not user-friendly, and often involve several components that reside outside of the tissue culture incubator. Given the wide utility of mechanical stimulation in in-vitro research, our aim was to create a turn-key research tool that bioengineers can deploy in their cell-stretch assays, without having to deal with the complexity and nuances of ad hoc experimental setups. Here, we present an open-source, battery-powered, dual-channel cyclic pneumatic pulse generator box that can reside within an incubator and is compatible with custom microfluidic cell stretch devices. Our method depends on generating pressure-vacuum pulses simply using a linear miniature pneumatic air cylinder actuated using a continuous servo motor. To the best our knowledge, this is a first example of a completely battery-powered, standalone system that doesn't have any peripherals residing out of the incubator. We provide a detailed list of different components as well as the step-by-step assembly process. We validate its performance in a cell stretch assay using a commercially available microfluidic chip. Our results show an acute stimulation of cyclic stretching over 8 h on human umbilical vein endothelial cells (HUVECs) resulted in preferential alignment of cells perpendicular to the axis of stretch.