(a) Sketch of the experimental setup; (b) images of the droplet formation captured by a high speed camera; (c)optical microscope image of three-compartment particles.
Optical images of Janus particles formed by microfluidic electrospray with the electric field strength of (a) 0 V/m, (b) 1 × 105 V/m, (c) 1.67 × 105 V/m, (d) 2.83 × 105 V/m, (e) 3.17 × 105 V/m, (f) 3.33 × 105 V/m, respectively. The flow rate of the fluid is constant (10 ml/h) and the scale bar is 1 mm; (g) a plot of the particle size as a function of the strength of the electric field; (h) an image of the droplet formation process captured by a high speed camera. In the microfluidic electrospray process, the flow rate is 10 ml/h and the electric field strength is 3.17 × 105 v/m.
(a) Optical microscope image (the scale bar is 500 μm) and (b) size distribution of Janus particles fabricated using our approach. The flow rate of the fluid is 5 ml/h and the electric field strength is 4.255 × 105 V/m.
Optical microscope images of Janus particles formed by electrospray with the fluid flow rate of (a) 4 ml/h, (b)10 ml/h, and (c) 16 ml/h, respectively. (d) Effect of the fluid flow rate on the particle size. The electric field strength of these three cases is 3.17 × 105 V/m. The scale bar is 1 mm.
Fluorescence microscope images of multi-compartment particles. Two kinds of Janus particles are presented: the volume ratios of the two sides are (a)1:1, (b) 2:1. (c) Microscope image of three-compartment particles. Conditions of fabrication for each image are as follows: Figure (a), flow rates are 2 ml/h in each side; applied electric field strength is 4.5 × 105 V/m; Figure (b), flow rates of the green and red precursor solutions are 4 ml/h and 2 ml/h respectively. The applied electric field strength is 4.5 × 105 V/m; Figure (c), flow rate of the precursor phases is 5 ml/h in each side while the applied electric field strength is 5 × 105 V/m. The scale bar is 200 μm.
Optical microscope images of Janus particles with magnifications of (a) 40 times, and (e) 100 times. (b), (c), (f), (g) Fluorescence microscope image of the Janus particles with stained cells encapsulated. Live cells are stained with a green fluorescent dye (calcein-AM), as shown in (b) and (f), while dead cells are stained with a red fluorescent dye (ethidium homodimer-1), as shown in (c) and (g); (d) and (h) are overlays of images captured by optical microscope and fluorescence microscope. The scale bar for the images with the magnification of 40 times is 1 mm while that for the images with the magnification of 100 times is 0.5 mm.
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