Designable microfluidic ladder network with gradually varying resistance for mass production of monodisperse droplets

Abstract

Controllable mass production of monodisperse droplets is crucial in various fields, ranging from scientific research to industrial applications, while microfluidic ladder networks have shown enormous potential in this regard. However, current design strategies often aim to mitigate the adverse effects of distribution channel resistance by increasing droplet generator resistance, which significantly elevates overall system pressure and reduces integration efficiency. In this paper, we introduce a design rule for ladder-type parallel microfluidic devices, referred to as the “gradually varying resistance rule.” In this approach, each droplet generator is designed with a distinct flow resistance, ensuring that the flow resistance between each droplet production unit and the fluid inlet is balanced. Single-phase flow simulations and droplet production experiments conducted on parallel devices with 50 droplet generators demonstrate that, compared to existing constant resistance rules, the gradually varying resistance rule not only ensures uniform fluid distribution but also improves device integration. Moreover, due to lower flow resistance, it allows for more efficient droplet production at the same driving pressure. The gradually varying resistance rule offers a rational framework for the efficient development of microfluidic ladder networks with uniformly distributed flow rates, facilitating the mass production of highly monodisperse droplets.