Viscous Withdrawal for Micro-jet and Micro-drop Production

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The study of microscale drop or jet generation has catalyzed the invention of numerous biomedical and industrial technologies. Existing shear-based technologies require active control of both the continuous and the dispersed phases, therefore limiting their capacity for large scale parallelization.


Researchers at Princeton University have invented a scalable method for controllable and high-throughput production of monodispersed micro-drops or uniform micro-jet (coefficient of variation of drop or jet diameter (CV) <5%). This selective viscous withdrawal system is comprised of a nozzle immersed in one fluid near a fluid-fluid interface, where the application of a withdrawal flow can cause the entrainment of the second fluid into the nozzle forming jets or droplets. Since the system only requires the control of the withdrawal flow rate, it promises greater capacity for scaling up of droplet or jet production.



• Manufacturing microparticles, microfibers, microdrops

• Drug and other active ingredient encapsulation

• Particle coating, smart capsule manufacturing

• Cell encapsulation, single cell analysis



• No active and independent control of continuous and dispersed phases required

• Greater capacity for scale-up of drop or jet production compared to existing methods

• Allows tuning the size of a jet or drops


Stage of Development

The inventors have tested the method in generating droplets and jets smaller than 10 microns in diameter using various immiscible systems including water-in-oil, oil-in-water and aqueous two-phase system. They also have constructed a prototype and recorded videos that are available for examination.




Howard Stone is the Donald R. Dixon ’69 and Elizabeth W. Dixon Professor and Chair for the Department of Mechanical and Aerospace Engineering. Professor Howard A. Stone received the Bachelor of Science degree in Chemical Engineering from the University of California at Davis in 1982 and the PhD in Chemical Engineering from Caltech in 1988. Following a postdoctoral year in the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge, in 1989 Howard joined the faculty of the (now) School of Engineering and Applied Sciences at Harvard University, where he eventually became the Vicky Joseph Professor of Engineering and Applied Mathematics. In 1994 he received both the Joseph R. Levenson Memorial Award and the Phi Beta Kappa teaching Prize, which are the only two teaching awards given to faculty in Harvard College. In 2000 he was named a Harvard College Professor for his contributions to undergraduate education. In July 2009 Howard moved to Princeton University.

Professor Stone's research interests are in fluid dynamics, especially as they arise in research and applications at the interface of engineering, chemistry, physics, and biology.  In particular, he and his group developed original research directions in microfluidics including studies and applications involving bubbles and droplets, red blood cells, bacteria, chemical kinetics, etc. He received the NSF Presidential Young Investigator Award, is a Fellow of the American Physical Society (APS), and is past Chair of the Division of Fluid Dynamics of the APS. For ten years he served as an Associate Editor for the Journal of Fluid Mechanics, and is currently on the editorial or advisory boards of New Journal of Physics, Physics of Fluids (until 31 December 2015), Langmuir, (until  31 December 2015), Philosophical Transactions of the Royal Society, Soft Matter, and is co-editor the (new) Soft Matter Book Series.  He is the first recipient of the G.K. Batchelor Prize in Fluid Dynamics, which was awarded in August 2008. He was elected to the National Academy of Engineering in 2009, the American Academy of Arts and Sciences in 2011 and the National Academy of Sciences in 2014.


Zehao Pan is a postdoctoral researcher in Dr. Howard Stone’s laboratory. He is currently studying the rheology of hydrogel microfibers, especially its gelation behavior through mechanical interlocking. Such gelation method could become a new way for creating the scaffold for 3D cell culture without the use of cytotoxic chemicals. As a PhD student, he used both theory and experiments to study nanoscale Ohmic heating, electrospray water-in-oil droplet generation and electrospray cell encapsulation for biomedical applications.


Janine Nunes is a postdoctoral researcher in Dr. Howard Stone’s laboratory. She is interested in the controlled synthesis and fabrication of novel micro-objects, such as microfibers and core-shell/hollow microspheres, using multiphase microfluidics to template the precursor liquid phases.


Intellectual Property Status

Patent protection is pending.

Princeton University is currently looking for Industry collaborators to further develop and commercialize this technology.




Prabhpreet Gill

Princeton University Office of Technology Licensing • (609) 258-3653•

Patent Information:
For Information, Contact:
Prabhpreet Gill
Licensing Associate
Princeton University
Zehao Pan
Janine Nunes
Howard Stone