Microfluidic soluto-hydrodynamics using interactive patterned wall-slip and oscillatory thermo-capillarity

Thermo-capillarity-induced Marangoni hydrodynamics and consequent solutal transport within a microfluidic, immiscible binary-fluid system are theoretically explored. The soluto-hydrodynamics is achieved by the application of decisive-sinusoidal thermal stimuli and suitable wettability patterns at the walls. The coupled momentum and energy balance equations are solved semi-analytically under creeping flow and quasi-deformed interface assumptions. The parametric influence of the thermal and the slip boundary conditions on the hydrodynamic transport phenomena in a microchannel is discussed. It is delineated that the thermal and the slip perturbations govern the vortex transport and stretching, respectively, while their interplay controls the solutal mixing efficiency of the system. The asymmetry in the boundary conditions leads to a non-zero discharge rate through the microfluidic domain, leading to localized net transport without any mechanical driving source. The discharge rate increases with the thermal perturbation amplitude and the slip length, but dependence on the slip length is vital only for higher values of thermal perturbation amplitude. Lastly, the solute transport in the system is also analyzed for a given set of inlet concentration profiles. The species transport equation is solved semi-analytically to obtain the concentration distribution within the microchannel. The outcomes of the work can play a pivotal role in upgrading microfluidic technologies to attain quick sample processing, mixing efficacy and thermo-capillarity-driven soluto-hydrodynamics.