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. Author manuscript; available in PMC: 2020 Jun 7.
Published in final edited form as: Lab Chip. 2019 Apr 24;19(11):1977–1984. doi: 10.1039/c9lc00054b

Figure 4. Chemical and physical optimization of exchangeable nozzles to enable the processing of polymers solutions.

Figure 4.

(a) Pristine fused silica nozzles were hydrophilic, which readily enabled the formation of O/W emulsions, but impaired the formation of polymer-laden W/O emulsions such as dextran solution in hexadecane. (b) Chemically treating the fused silica with fluorinated silane (c) resulted in less hydrophilic nozzles that were compatible with the production of polymer-laden W/O emulsions. (d-e) Alternatively, fused silica (FS) nozzles could be physically modified with a UV-protective polyimide (PI) coating to prevent nozzle clogging during processing of photocrosslinkable polymers. (f) The polyimide coating reduced the relative UV transmission by more than 4-fold and enabled (g,h) continuous and stable production of photocrosslinked polymer microspheres under UV irradiation by preventing nozzle clogging (i) over a wide range of UV intensities as compared to non-coated nozzles. Nozzle clogging, incompletely photocrosslinked PEGDA, and completely photocrosslinked PEGDA are indicated with red, blue, and green squares, respectively. Scale bars indicate 200 μm. * indicates significance with p <0.01.