Manipulation of micro/nanolitre fluids with non-wetting interfaces

Abstract

Dexterous manipulation of micro/nanolitre fluids with minimized volume loss is crucial for many fields. The inter-surface transfer, on-plane transport, and quasi-static aliquoting of droplets/bubbles in a precise and effortless manner still remain challenging because of the complicated liquid/solid contact. We propose strategies and physical/chemical designs that is integrated with the non-wetting interfaces to manipulate micro/nanolitre fluids in a loss-free manner. The proposed solutions are experimentally and theoretically studied.

To losslessly transfer and aliquot droplets, we create a mechano-regulated surface consisting of a background mesh and a movable microfibre array with contrastive wettability. The adhesion of this mechano-regulated surface to liquid droplets can be reversibly switched through mechanical reconfiguration. Using the surface, micro-/nanolitre liquid droplets can be in situ captured and released and nanolitre droplets with controlled volume can be aliquoted from a bulk reservoir.

To remotely transport droplets, we design a pyroelectro-trapping on superhydrophobic surfaces platform where droplets’ motions can be photo-controlled. Through photothermal and pyroelectric effects, light energy is converted into local non-uniform electric field which traps and guides the underlying droplets through dielectrophoretic forces. Droplets as well as liquid puddles can be transported in a loss-free manner across a wide platform with high spatial precision offered by light-controlled methods.

To directionally transport mass of bubbles, we prepare a spatially-lubricated surface with high-resolution lubricant patterns through spontaneous dewetting on surfaces of contrastive liquid affinity. The lubricant-free regions are non-adhesive to bubbles. By contrast, bubbles are confined on lubricated regions with their high mobility well preserved. On the pre-programmed surface, the transporting behaviour of mass of tiny bubbles can be defined and controlled.

The microscopic interfacial interactions as well as the macroscopic motion dynamics are physically elucidated, allowing a fine control over the fluids. The applications of such precise fluidic manipulation are demonstrated in diverse fields, including micro-reaction, gas collection, and analytes detection.