Generating Turbulence and Enhancing Mixing in a Microchannel by Using Traveling Wave Boundaries

Mixing enhancement in microchannels presents a formidable challenge due to the inherent difficulty of inducing turbulence at such small scales. This study introduces an innovative active method to augment mixing by leveraging the effects of traveling wave vibrations on channel walls. Through meticulous simulation and experimental validation under carefully selected parameters, we have observed a substantial enhancement in mixing efficiency. The introduction of traveling waves on the channel walls propels the flow adjacent to the boundary, thereby initiating a robust bulk flow within the microchannel. As the Reynolds number (Re) surpasses a critical threshold, the flow undergoes a transition to instability, which significantly amplifies the mixing efficiency, particularly for higher wavenumbers. Our findings reveal that the mixing efficiency achieved with traveling wave walls surpasses that of standing wave walls by a considerable margin. In the turbulent flow regime, we have derived a relationship that characterizes mixing efficiency through the Nusselt number, expressed as $Nu \sim Re^{1.2}$. This vibration-assisted method, applied beneath the microchannel, is not only facile to fabricate, but also exhibits adaptability across a spectrum of lab-on-a-chip applications.