A quantitative study of the dynamic response of compliant microfluidic chips in a microfluidics context

Polydimethylsiloxane (PDMS) is a widely used material for microfluidic devices due to its low cost, superior optical properties and fast iterative design process. Its softness however creates challenges for the device design and operation because part of the applied pressures contributes to deform chips instead of controlling the flow. The resulting dynamic behaviour is often ignored in passive microfluidic that focuses on the static behaviour of the chip, however, can cause low accuracy to active microfluidic that actuates flow frequently. Therefore, understanding the dynamic behaviour of microfluidic devices due to material compliance is of fundamental and practical importance. In this study, the microfluidic chip compliance is carefully considered by separating it from the sample tubing compliance. The capacitance is retrieved by assuming a symmetric RC circuit based on the experimentally determined time constant and chip resistance. The experimental capacitance is compared to a theoretical formula for chip designs with different height-to-width ratios and height-to-length ratios and for various fluids. The accuracy is within one order of magnitude that is much closer than previous approximations.