Microfluidics:
The Technology
Microfluidics for generation of microparticles through chemical gelation
In this work, we developed a microfluidic platform for generation of alginate microparticles that works on the principles of droplet coalescence and chemical gelation. The hybrid Polydimethylsiloxane (PDMS)-Glass microfluidic device contains a combination of the Co-flow and T-junction configurations. The controlled fusion of alginate and calcium chloride droplets generated from co-flow and T-junction channels respectively, in the presence of the outer flowing silicone oil, results in crosslinking and gelation of sodium alginate to produce calcium alginate microparticles.
Incorporation of electric field for generation of microparticles
Electric field is employed for manipulation of droplets to reduce size of microbeads. We demonstrated that microfluidics-based gelation coupled with on-chip application of electric fields is a promising cell encapsulation technology. Using chemical gelation achieved through on-chip coalescence of sodium alginate droplets and calcium chloride plugs, in the presence of applied electric fields, we were able to generate alginate microparticles. The controlled droplet size coupled with complete on-chip gelation demonstrated here can be employed for several encapsulation-based applications.
Electro-hydrodynamics coupled with photopolymerization for generation of microparticles
Coupling electro-hydrodynamics with photopolymerization, our team generated polyethylene glycol diacrylate (PEGDA) microparticles and hydrogels using a hybrid microfluidic device. PEGDA droplets formed in the presence of an electric field were solidified post exposure to UV to give rise to microparticles. Furthermore, we tuned the size of microparticles by varying the flow rates, the viscosity, monomer concentrations, applied voltage. Ease of fabrication, continuous microparticle generation with high monodispersity, makes our 3D hybrid microfluidic device better than some of the existing techniques.
Complete on-chip fabrication of alginate microcapsules
Core-shell microcapsules are currently being used for studying cell-cell interactions and for drug delivery. Our lab also focuses on designing devices for micro-capsule generation. We have fabricated a droplet based microfluidic device for generation of alginate microcapsules with single and double liquid cores. In the case of double core microcapsules, the two cores were well separated by alginate layer ensuring their long-term stability. Our device has advantages in terms of continuity of the process, control over core stability, and non-damage to cells.
Microcapsule generation in presence of electric field
Chemical gelation in the presence of an electric field is a great approach to generate single/ double emulsions. The complete on-chip generation of microcapsules by incorporation of an electric field and chemical gelation established by our team can be used for achieving significant reduction of particle size when compared to the other existing non-EDH electrohydrodynamic systems. Crucially, the method provides a cheap way to apply electric field on a chip using liquid electrodes rather than expensive electrode patterning. We were able to generate alginate microparticles and microcapsules of uniform sizes with a liquid core using this approach. The system holds great applications especially in the fabrication of biomaterials and scaffolds.
Microfiber generation using a PDMS-glass hybrid microfluidic device
The size of fibers and extent of coiling of generated fibers can be precisely controlled using microfluidic based microfiber fabrication. We designed and fabricated a hybrid PDMS-glass microfluidic device that could be used for on-demand generation of both nonwoven and single fiber within the same device. We implemented a coflowing solvent removal technique to generate poly (ethylene oxide) (PEO) fibers. Furthermore, we controlled the extent of coiling by employing a complementary flow towards the downstream end of the fiber solidification. We also could transition between nonwoven and single microfibers by varying the complementary flow.