Liquid metal droplet generation based on T-junction microchannels

Galinstan liquid metal remains liquid at room temperature and exhibits unique physical properties including fluidity and high electrical conductivity, and its manipulation is a subject of extensive research interest. In contrast to existing control methods, such as electric and magnetic fields, we focus on a novel and efficient approach based on generating liquid metal droplets through microchannels. The present investigation mainly deals with generating liquid metal droplets through establishing a two-dimensional computational model based on the phase-field method for the droplet microfluidics in a T-junction structure. To enhance its performance, a constraint structure is added to expand the adjustment range of droplet formation. The constraint structure and increasing flow rate enhance the viscous shear effect, which reduces the droplet formation length and increases the generation frequency. Polymethyl methacrylate and pressure-sensitive adhesive are laser-cut to fabricate the microchannels. A peristaltic pump is utilized as the driving device, and a high-speed camera is employed to record the liquid metal droplet formation process. Both reducing the constraint ratio and increasing the flow ratio result in accelerated shear rate and increased droplet formation frequency, which is consistent with the simulation results. In experiments, the constraint structure enhanced the viscous shear effect, and relocation of the fracture location was observed. In addition, the high surface tension and inertia of the liquid metal released energy during droplet breakup, leading to noticeable oscillation and deformation of the droplet. Both the simulation and experimental results provide guidelines for the application of liquid metal generation in reconfigurable metasurfaces.