Topology optimization of multichannel step emulsification droplet generators

Microfluidics is pivotal in producing monodisperse microemulsions and microspheres. However, lower output efficiency hinders its practical application. Although multichannel droplet generators offer a promising solution for increased productivity, their design is inherently complex, and achieving uniform fluid distribution across channels is a significant challenge. Hence, in this paper, a novel rapid-design approach is introduced for multichannel droplet generators and employs topology optimization to enhance the structure, leading to significant improvements in droplet generation efficiency and uniformity. It can automatically generate a multichannel droplet generator structure that meets experimental conditions within five hours and is compatible with 3D printing technology. By employing topology optimization, the design achieves an average inter-channel flow rate variation of less than 1%, even with 81 channels, while reducing the inlet-outlet pressure drop by 19.75% compared to unoptimized configurations. The optimized device can produce both water-in-oil (W/O) and oil-in-water (O/W) droplets at a maximum throughput of 65 mL·min⁻¹, with a coefficient of variation (CV) below 5%, ensuring excellent monodispersity. Moreover, the topology optimization approach provides a comprehensive analytical framework for droplet generators with a matrix of microchannels, thereby facilitating rational design and scalability. Graphical abstract