On-demand micro-encapsulation utilizing on-chip synthesis of semi-permeable alginate-PLL capsules

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. Threelayered 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 CaCl 2 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.

Automated dynamic inlet microfluidics system: 3D printer adaptation for cost-effective, low volume, on-demand multi-analyte droplet generator

“…The maximum CV% achieved for volume of droplets in a train within the cylindrical section of the well is 2.51% (flow rate: 150 μL min −1 , target droplet volume: 1.0 μL), which is better than the accuracy achieved in the conical section of the well. The improvement is due to the fact that the eqn (3) relates Δh to ΔVolume more accurately than the modelled eqn (5). This proves that the system can produce a train of droplets with low variance in volume throughout the well.…”

“…In section 2.2.1, two equations are presented for the calculation of Δh. In the previous section, eqn (5) is used as the volume of analyte dispensed in the well is 30 μl, thus the operating in the conical section of the well in the well plate. However, if large volume (e.g.…”

“…[1][2][3] Droplets in dual-phase microfluidics are isolated from each other and the tubing walls because of the immiscibility of the dispersed and continuous phase, which encapsulates the droplet with a thin film of the continuous phase. 4 This allows each droplet to act like a microreactor, a feature particularly useful for chemical or biochemical synthesis, 5,6 etc. The first step of droplet microfluidics is the generation of an analyte droplet with the required volume.…”