Continuous and Membrane-less Filtration of Colloidal Particulates

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Continuous and Membrane-less Filtration of Colloidal Particulates

Princeton Dockets # 17-3285-1, 16-3249-1

A novel method and device for separating suspended colloidal particles from aqueous stream without the use of a physical filter that is energy efficient, chemically non-invasive, and continuous. This method offers the potential to transform the cost of providing drinking water, in both high- and particularly low-income countries. Further, the superior performance of the process compared to filtration - removal of all but 0.0005% of the target particles – gives it application in a range of ‘med tech’ - e.g. dialysis – and food & beverage processes.

The process is based on the principal of diffusiophoresis, which uses dissolved CO2, supplied to one side of a flowing aqueous stream, produces a transverse chemical gradient of ions (primarily H+ and HCO3-), which in turn leads to movement of suspended particles to one side of the flowing stream and so effectively produces a continuous flow free of particulate matter. Diffusiophoresis with dissolved CO2 promises a cost-effective alternative to filtration for:

•       large-city water utilities in both high- and low-income countries;

•       communities in low-income countries not connected to a distribution network – the 660m above;

•       applications requiring clean water as an input, particularly those for which the 100-1000 times greater level of purity achievable with diffusiophoresis than with filtration is of value. An example already identified is dialysis equipment, particularly for home-based dialysis;

•       on demand lab on chip device to supply particulate free and potentially sterile aqueous stream


through reductions in:

•       operating cost – energy, chlorination / ultraviolet treatment, cleaning and maintenance;

•       capital cost – of pumps, bacterial disinfection units, and longer life;

•       operating (maintenance) expertise - a particular benefit in low-income countries;


together with:

•       greater capacity flexibility, enabling treatment in previously unserved rural communities in low-income countries, and localising treatment to avoid re-contamination in distribution;

•       avoidance of toxic disinfection by-products associated with free chlorine disinfection.



Featured in the Economist:

Shin, S. et al. “Membraneless water filtration using CO2.” Nature Communications, 8, 15181 (2017) Doi: 10.1038/ncomms15181

Ault, J.T. et al. “Diffusiophoresis in one-dimensional solute gradients.” Soft Matter, 13, 14, 9015-9023 (2017). Doi: 10.1039/c7sm01588g


Intellectual Property & Development Status

Patent protection is pending.

PCT application PCT/US2017/049819 titled “Device and Methods for Continuous Flow Separation of Particles by Gas Dissolution” was filed on 2017.09.01 filed. Publication number wo 2018/048735.

US nonprovisional application number 15/913,649 titled “Gradient Induced Particle Motion in Suspensions” was filed on 2018.03.06. Publication number US 2018-0257054A1.

The technology has been demonstrated at lab scale. Prof. Stone is seeking commercial partner for further validation of the technology and to conduct scale up studies.


The Faculty Inventor

Howard A. Stone is the Donald R. Dixon and Elizabeth W. Dixon Professor in Mechanical and Aerospace Engineering and Chair. Howard Stone's research interests are in fluid dynamics, especially as they arise in research and applications in transport phenomena at the interface of engineering, chemistry, physics, biology and applied mathematics.  His research group has developed original research directions in the area of complex fluids and microfluidics including studies and applications involving bubbles and droplets, red blood cells, bacteria, chemical kinetics, etc. Professor Stone is a Fellow of the American Academy of Arts and Sciences and is a member of the National Academy of Sciences and the National Academy of Engineering.  In 2008, Stone was the winner of the inaugural Batchelor Prize sponsored by the Journal of Fluid Mechanics for the breadth and depth of his research over a 10-year period (1998-2007) and for his widely acknowledged leadership in fluid mechanics. 



Linda Jan

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


Patent Information:
For Information, Contact:
Tony Williams
Associate Director
Princeton University
Sangwoo Shin
Orest Shardt
Patrick Warren
Howard Stone