Rapid Fabrication of a Pumpless PDMS Microfluidic Device Using CO2 Laser Micromachining for Automated Formation of Monodisperse Water-in-Oil Droplets

To form monodisperse water-in-oil droplets in a fully automated fashion, we fabricated a pumpless microfluidic device consisting of top and bottom polydimethylsiloxane slabs. All microstructures required for droplet formation were directly patterned on the surfaces of two polydimethylsiloxane slabs using CO2 laser micromachining, facilitating rapid fabrication of the current device. This device formed uniformly sized droplets (a coefficient of variation for droplet diameters of <4%) at a rate of ∼220 droplets/s. Microstructures such as microfluidic channels and an array of orthogonal microgrooves were directly patterned on surfaces of polydimethylsiloxane slabs by CO2 laser micromachining, to fabricate a pumpless microfluidic device capable of forming water-in-oil droplets. After degassing of the developed device, an aqueous phase and an oil phase were loaded into the device. This enabled fully automated formation of monodisperse droplets.