Shum, Ho CheungVarnell, JasonWeitz, David A.2019-10-092012Shum, Ho Cheung, Jason Varnell, and David A. Weitz. 2012. “Microfluidic Fabrication of Water-in-Water (w/w) Jets and Emulsions.” Biomicrofluidics6 (1): 012808. https://doi.org/10.1063/1.3670365.1932-1058http://nrs.harvard.edu/urn-3:HUL.InstRepos:41511293We demonstrate the generation of water-in-water ( w/w) jets and emulsions by combining droplet microfluidics and aqueous two-phase systems ( ATPS). The application of ATPS in microfluidics has been hampered by the low interfacial tension between typical aqueous phases. The low tension makes it difficult to form w/w droplets with conventional droplet microfluidic approaches. We show that by mechanically perturbing a stable w/w jet, w/w emulsions can be prepared in a controlled and reproducible fashion. We also characterize the encapsulation ability of w/w emulsions and demonstrate that their encapsulation efficiency can be significantly enhanced by inducing formation of precipitates and gels at the w/w interfaces. Our work suggests a biologically and environmentally friendly platform for droplet microfluidics and establishes the potential of w/w droplet microfluidics for encapsulation-related applications.en-USJournal Article2019-10-0910.1063/1.3670365