Diffusioosmotic flow in a soft microfluidic configuration induces fluid-structure instability

Diffusioosmotic flow, driven by solute concentration gradients, is a widely used method for fluid manipulation in microfluidic devices, often fabricated from soft materials such as PDMS. We show that such soft diffusioosmotic flow systems may exhibit fluid-structure instability. To provide insight into the underlying instability mechanism, we develop a theoretical model describing the interaction between diffusioosmotic flow and an elastic substrate. We find that above a certain concentration gradient threshold, negative pressures induced by diffusioosmotic flow cause the collapse of the elastic top substrate onto the bottom surface.