Three-dimensional valve-based controllable PDMS nozzle for dynamic modulation of droplet generation

In this work, we developed a shape-controllable nozzle inside a multilayer PDMS microchip. The nozzle was able to control the shape of the fluid channel in three dimensions. All the four walls of the fluid channel were comprised of pneumatic PDMS membrane valves, and their deformation was controlled by air pressure. As both the limitation of the fluid flux and the shape of the fluid channel were adjustable spatially in three dimensions, this valve-based nozzle generated droplets with less response time and in a more effectively controlled manner comparing to conventional droplet devices. It could also function as a microinjector to modulate the compositions of droplets precisely and continuously. In addition, the nozzle was able to form a specific shape to generate core–shell particles.