Tuning the hydraulic resistance by swelling-induced buckling of membranes in high-aspect-ratio microfluidic devices

Controlling fluid flow in microfluidic devices and adapting it to varying conditions by selectively regulating hydrodynamic properties is of critical importance, as the field of microfluidics faces increasingly complex challenges in its wide range of applications. One way to manipulate flows in microfluidic devices is to introduce elastic elements that can be actively or passively deformed. In this work, we developed a membrane-based microfluidic device that allows us to study the deformation of swollen thin membranes as a function of the volume fractions in binary mixtures - here isopropanol and water. Furthermore, the membrane deformation can be used to control pressure-driven flows within the device. The device consists of two microfluidic channels separated by a thin membrane that deforms by a buckling-based mechanism, when the isopropanol volume fraction of the solvent flowing through it exceeds a certain volume fraction. The buckling membrane causes a sinusoidal height variation in both adjacent channels, resulting in a large increase in hydraulic resistance. We show that buckling-based deflections of elastic membranes can be used to amplify small changes in the degree of swelling to produce large changes in the microchannel geometry of the device, sufficient to manipulate the flow rate of pressure-driven flows in the microdevice.

Automated summary

In this study, a membrane-based microfluidic device was developed to investigate the deformation of thin membranes in relation to the volume fractions of binary mixtures, and it can be used to control pressure-driven flows within the device by membrane deformation. When the volume fraction of isopropanol in the solvent exceeds a certain threshold, the membrane undergoes buckling deformation, resulting in sinusoidal height variations in adjacent channels and an increase in hydraulic resistance. The study demonstrates that buckling-based deflections of elastic membranes can amplify small changes in swelling and significantly manipulate the flow rate in microfluidic devices.