Microfluidics-based generation of cell encapsulated microbeads in the presence of electric fields and spatio-temporal viability studies.

Microfluidics based techniques for generation of cell-laden microbeads are emerging as an attractive route to 3D cell encapsulation due to the precise control provided by microfluidics. However, existing microfluidics based cell encapsulation methods are restricted to 2D planar devices and use of passive methods for droplet generation. In this work, we report the development of a 3D glass-PDMS (polydimethylsiloxane) hybrid device for complete on-chip generation of cell-laden alginate beads in the presence of electric fields. The 3D hybrid device allows application of electric fields for active control of droplet (sodium alginate) size without the need for electrode patterning or liquid electrodes. Chemical gelation is achieved through on-chip coalescence of sodium alginate droplets and calcium chloride plugs, generated using coflow and T-junction geometries respectively. Using this approach, we successfully encapsulate E. coli cells (with viability ∼90 %) into alginate microbeads and perform comprehensive spatio-temporal growth and viability studies. The active control of droplet size coupled with complete on-chip gelation demonstrated here is a promising technology for cell encapsulation with applications such as cell therapy, organ repair, biocatalysis, and microbial fuel cells.