UCLA

Injectable hydrogels are widely used as in situ scaffolds to support tissue regrowth but suffers from degradation before tissue reformation. As shown in our last paper, microporous Annealed Particle (MAP) gels can provide a stably linked interconnected network for tissue regrowth. While current applications of MAP gel composed of 4-arm poly(ethylene) glycol-vinyl sulphone (PEG-VS) backbone is limited to mimicking soft tissues new backbone material 8-arm PEG-VS increases the range of gel stiffness. Stiffer gel scaffold facilitates cell infiltration rate and expands application to tissues with greater mechanical movement. However, backbone and cross-linker materials can react in the channel and form polymers due to transverse diffusion, which causes jetting in the device and interrupts monodisperse droplet production. Here we present a three-inlet flow-focusing droplet generator which can prevent polymerization in the channel by controlling the width of a middle buffer stream. We have shown that it enables 4 times longer production time for previous material and at least 2 times longer production time for new material. MAP gel with a higher stiffness and annealing force is achieved using the 3-inlet device. The 3-inlet device empowers mass production of MAP gel, leading to higher reproducibility of MAP gel related research studies. The study of the middle buffer stream gives ideas to other flow-focusing microfluidics system where two reactants need to be separated before encapsulation in droplets.