Stimuli-controlled fluid control and microvehicle movement in microfluidic channels

Integration of stimuli-responsive materials into microfluidic systems provides a means to locally manipulate flow at the microscale, in a non-invasive manner, while also reducing system complexity. In recent years, several modes of stimulation have been applied, including electrical, magnetic, light and temperature, among others. To achieve remote control of flow in microfluidics using external stimulation, two main approaches have emerged in the recent years:\ud 1. Control of flow through stimuli-induced actuation of microfluidic components (valves, pumps, mixers, flow sorters), most often fabricated from soft polymeric materials;\ud 2. Stimuli-controlled manipulation of discrete micrometer-sized “vehicles” (droplets, beads, Janus particles, etc.) through localized induced changes in wettability or surface tension.\ud The focus of this chapter will be to identify and compare the similarities and underlying mechanisms employed in the current state of the art research in stimuli-controlled fluid control and micro-vehicle movement fields. It will also endeavor to propose possible directions for the evolution of these areas of research