Thermal field-actuated multifunctional double-emulsion droplet carriers: On-demand migration, core release and released particle focusing

Microcarriers enabling efficient cargo transportation and targeted release are significant for lots of applications such as drug delivery and sample preservation. Herein, we present a universal method for the integrated manipulation of double-emulsion droplet carriers including microcarrier migration, core release and released particle focusing based on thermal fields. Double-emulsion droplet carriers with typical shell material of polymethylphenyl silicone oil are prepared by droplet microfluidics. In the designed microfluidic platform, by orderly actuating the microheaters arranged at the bottom of microchannel, the microcarrier can pass through the sinuous transport channels from the inlet to the central chamber of microchannel under the buoyancy flow induced Stokes drag, demonstrating the satisfactory transportation ability of thermally controlled micro carriers. When the microcarrier reaches the targeted region, the core release behavior will be triggered by the Marangoni effect if the microheater in central chamber is constantly energized by DC signal, followed by the release of encapsulated functional particles. Finally, the released particles will be focused to central region of microchannel under the driven of convection flow as the power applied on central microheater goes on. The presented method used for droplet carrier migration, core release and released particle focusing are demonstrated by systematic experiments. And the practical usability of this approach is validated by the migration, release and culture of yeast cells through double-emulsion droplet carriers. Therefore, this technique used for the transportation and release of droplet carriers can be promising for many applications.