Macrodrop-Impact-Mediated Fluid Microdispensing

High-resolution fluid dispensing techniques play a critical role in modern digital microfluidics, micro-biosensing, and advanced fabrication. Though most of existing dispensers can achieve precise and high-throughput fluid dispensing, they suffer from some inherent problems, such as specially fabricated dispensing micronozzles/microtips, large operating systems, low volume tunability, and poor performance for low surface tension liquids and liquids containing solid/liquid additives. Herein, the authors propose a facile, low-frequency micro dispensing technique based on the Rayleigh-Plateau instability of singular liquid jets, which are stimulated by the air cavity collapse arising in the impact of microliter drops on non-wetting surfaces. This novel dispensing strategy is capable to produce single microdrops of low-viscosity liquids with a tunable volume from picoliters to nanoliters, and the operational surface tension range covers most laboratory solvents. The dispensing function is implemented without using small-dimension nozzles/tips and enables handling diverse complex liquids. Moreover, the rather simple operating platform allows the integration of the whole dispensing function into a handy portable device with a low cost. Employing this microdispensing technique, the authors have controlled microchemical reactions, handled liquid samples in biological analysis, and fabricated smart materials and devices. The authors envision that this rational microdrop generator would find applications in various research areas.