PDMS filter structures for size-dependent larval sorting and on-chip egg extraction of C. elegans

C. elegans-based assays require age-synchronized populations prior to experimentation to achieve standardized sets of worm populations, due to which age-induced heterogeneous phenotyping effects can be avoided. There have been several approaches to synchronize populations of C. elegans at certain larval stages; however, many of these methods are tedious, complex and have low throughput. In this work, we demonstrate a polydimethylsiloxane (PDMS) microfluidic filtering device for high-throughput, efficient, and extremely rapid sorting of mixed larval populations of C. elegans. Our device consists of three plasma-activated and bonded PDMS parts and permits sorting of mixed populations of two consecutive larval stages in a matter of minutes. After sorting, we also retain the remaining larval stage of the initially mixed worm population on the chip, thereby enabling collection of the two sorted larval populations from the device. We demonstrated that the target larvae could be collected from a mixed worm population by cascading these devices. Our approach is based on only passive hydrodynamics filter structures, resulting in a user-friendly and reusable tool. In addition, we employed the equivalent of a standard bleaching procedure that is practiced in standard worm culture on agar plates for embryo harvesting on our chip, and we demonstrated rapid egg extraction and subsequent harvesting of a synchronized L1 larvae population.