Ultra-monodisperse droplet formation using PMMA microchannels integrated with low-pulsation electrolysis micropumps

This paper presents a method for stable and reliable generation of ultra-monodisperse oil-in-water (O/W) droplets using poly(methyl methacrylate) (PMMA) microchannels integrated with three low-pulsation electrolysis micropumps (EMPs) on a chip. The EMPs are proposed to be driven by constant electric current with the optimized interdigital electrodes to achieve a smaller pulsations in the output flow. The flow pulsations are characterized via a fluidic comparator, and the results show that smaller pulsations in the flow rates can be achieved, thus polydispersity of the generated droplets is lowered. Both dripping and alternating droplets generation are demonstrated. In dripping scenario, highly uniform droplets ranging from 465 μm to 360 μm with a polydispersity index (σ) value between 1.3% and 2.6% are achieved. In alternating scenario, monodisperse droplets ranging from 441 μm to 342 μm with σ value between 1.8% and 2.8% are also achieved. Based on the proposed modular assembly process, the PMMA channels and/or the substrate can be easily replaced and re-assembled to realize other functions such as flow rate measurement or flow pulsations characterization. In all, the proposed microfluidics platform provides robust ultra-monodisperse droplet generation capability which could facilitate the development of high-performance droplet-based microsystems.