Abstract
This article presents an on-demand, multi-step synthesis scheme that is capable of forming semi-permeable micro-capsules on an integrated microfluidic system. Emulsion droplets functioning as templates and reactors are employed to realize the synthesis process. Three-layered PDMS micro-devices with pneumatically actuated diaphragm valves constructed on top of specially designed fluidic-channels are utilized to control the droplets and, consequently, the encapsulation process. A PDMS molding and bonding process is used to fabricate the proposed microfluidic devices. In the prototype demonstration, relatively small Na-alginate droplets are metered, trapped, and then drawn into relatively large CaCl2 droplets, while they react and form solid Ca-alginate micro-capsules on the interfaces. In addition, entrapment and transfer of the resulting capsules can also be performed on the same microfluidic system to further process Ca-alginate into semi-permeable alginate-poly-l-lysine (PLL). It has been demonstrated that: (1) both emulsion droplets and solid capsules could be manipulated; (2) multi-step reactions could be performed on droplet-in-droplet interfaces to synthesize alginate-PLL capsules; and (3) on demand, controlled encapsulation could be achieved on an integrated microfluidic system. As such, the demonstrated multi-step synthesis scheme could potentially fulfill the real-time controllability on micro-encapsulation, which is desired for a variety of biological and medical applications.
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Acknowledgments
This work was supported in part by the National Center for High-performance Computing and the National Science Council of Taiwan under Contract No. NSC 99-2628-E-007-028. The demonstrated systems were fabricated in the ESS Micro-fabrication Lab. at National Tsing Hua University, Taiwan.
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Chang, SC., Su, YC. On-demand micro-encapsulation utilizing on-chip synthesis of semi-permeable alginate-PLL capsules. Microfluid Nanofluid 10, 1165–1174 (2011). https://doi.org/10.1007/s10404-010-0744-7
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DOI: https://doi.org/10.1007/s10404-010-0744-7