A self-sufficient micro-droplet generation system using highly porous elastomeric sponges: a versatile tool for conducting cellular assays

Here, we present a self-sufficient droplet generation system using a highly porous elastomeric sponge. Upon manual compression, aqueous solutions can be loaded into or unloaded from the sponge. The surface of the sponge accommodates hundreds of small orifices, which facilitate generation of microscale droplets when compressed inside an oil container. The physics underlying the generation and size distribution of droplets is explored. Proof-of-concept experiments demonstrate the capability of this method for encapsulation of human monocytes inside droplets. The droplets are chemically isolated, mechanically stable, and do not evaporate due to the presence of oil in the microwell. The cells settle at the lowest surface of the droplets without using any secondary immobilisation mechanisms. These features facilitate chemical stimulation and microscopic analysis of encapsulated cell clusters in a quick and parallel manner. The simplicity and self-sufficiency of this method makes it suitable for conducting various droplet-based cellular assays.