Fig. 1.

(A) An image of the microfluidic chip showing the flow focusing geometry of the junction (14 µm × 17 µm, highlighted in a yellow dotted box). The phase-shift double emulsion (PSDE) was generated by pumping the inner (W₁/PFC) and outer (W₂) fluids at 1 and 10 µL/min, respectively. The enlarged features display schematics of two similarly-sized PSDEs each containing a different PFC phase and payload: (I) perfluorohexane (PFH) and Alexa Fluor 488-labeled dextran (AF₄₈₈), and (II) perfluorooctane (PFO) and Alexa Fluor 594-labeled dextran (AF₅₉₄). (B) Picture of ultrasound (US) exposure setup. The plastic balls at the water surface maintain the temperature and dissolved gas concentration in the water tank. Acoustically-responsive scaffolds (ARSs), containing PSDEs, were polymerized in a BioFlex plate which was positioned on the surface of the water tank. US was applied through the silastic well bottom. (C) Schematics of side views of ARSs containing PFH-AF₄₈₈ as well as PFO-AF₅₉₄ exposed to different US parameters (i.e., frequency and pulse duration) resulting in different responses in PSDEs. Sequential release of AF₄₈₈ and AF₅₉₄ was achieved using high frequency US followed by low frequency US, respectively. Scale bar: 20 mm. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)