Method and electro-fluidic device to produce emulsions and particle suspensions

Patent metadata

Field	Value
Publication number	US-9789451-B2
Application number	US-201013392908-A
Country	US
Kind code	B2
Filing date	Aug 30, 2010
Priority date	Aug 28, 2009
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

The invention refers to a method, and to a device to produce emulsions and particle suspensions by using electro-hydrodinamic forces and microfluidics This combined use allow the production of droplets with mean diameters which may be either smaller than those obtained in conventional microfluidic devices or larger than those obtained by electrospray, bridging the gap between the two methods acting independently.

First claim

The invention claimed is:

1. A system comprising:
a micro-channel having a central axis along its length;
a pump for pumping a dielectric fluid in a first flow direction within the micro-channel;
a first capillary tip located within the micro-channel and extending along the central axis of the micro-channel for a portion of the length of the micro-channel;
a pump for pumping a first conducting fluid in the first flow direction within the first capillary tip;
a second capillary tip located downstream in the first flow direction from the first capillary tip, the second capillary tip located within the micro-channel and extending along the central axis of the micro-channel for a portion of the length of the micro-channel;
an annular gap extending the length of the second capillary defined by the difference between the diameters of the micro-channel and the second capillary tip;
a pump for pumping a second conducting fluid in a second flow direction within the second capillary tip; and
an electrical potential generator;
wherein the dielectric fluid is immiscible or poorly miscible with the conducting fluids;
wherein the second flow direction of the second conducting fluid flows counter with respect to the first flow direction of the dielectric fluid;
wherein upon flow of the dielectric, first and second fluids a steady state interface is formed separating the dielectric fluid and the first conducting fluid;
wherein upon flow of the dielectric, first and second fluids, when an electrical potential difference is applied by the electrical potential generator to the first capillary tip and the second capillary tip, a steady state capillary jet is formed, producing a stream of charged droplets which move towards the steady state interface under the combined action of the electric and hydrodynamic forces; and
wherein once the droplets reach the steady state interface they discharge and form an emulsion that leaves through the annular gap.

2. The system according to claim 1 , wherein upon flow of the dielectric, first and second fluids, the steady state interface is located in between the first and second capillary tips.

3. The system according to claim 1 , wherein the system comprises:
a number N of feeding tips with (N≧2), wherein one of the feeding tips is the first capillary tip; and
N pumps, one each for each feeding tip, for pumping conducting fluid in the first flow direction within each of the N feeding tips, wherein one of the pumps is the pump for pumping the first conducting fluid, being an inner conducting fluid, in the first flow direction within the first capillary tip;
wherein upon flow of the dielectric, first and second fluids, in the first capillary tip flows the inner conducting fluid at a flow rate Q 1 whilst a generic conducting fluid Li-th flows at a generic flow rate Q i through the Ti-th tip (2≦i≦N); and
wherein upon flow of the dielectric, first and second fluids, the N feeding tips are arranged such that the L(i−1)-th conducting fluid surrounds the Ti-th tip and the tips, that are immersed in the dielectric fluid, which is flowing at a rate Q D .

4. The system according to claim 1 , wherein the diameters of the capillary tips are between 0.001 mm and 5 mm.

5. The system according to claim 1 , wherein upon flow of the dielectric, first and second fluids, the first conducting fluid flows at a flow rate of Q 1 in the first capillary tip, and the second conducting fluid flows at a flow rate of Q 2 in the second capillary tip;
wherein upon flow of the dielectric, first and second fluids, the flow rate Q 1 -Q 2 is between 10 −15 m 3 /s and 10 −7 m 3 /s; and
wherein upon flow of the dielectric, first and second fluids, the flow rate Q D of the dielectric fluid and the flow rate Q 1 of the first conducting fluid are both between 0 and 10 −1 m 3 /s.

6. The system according to claim 1 , wherein upon flow of the dielectric, first and second fluids, the dielectric conductivity of the first and second conducting fluids is between 10 −12 and 10 6 S/m.

7. The system according to claim 1 , wherein upon flow of the dielectric, first and second fluids, the absolute value of the electric potential difference is between 1 V and 100 kV for obtaining a separation between the first capillary tip and the steady state interface of between 0.001 mm and 10 cm.

8. The system according to claim 1 , wherein upon flow of the dielectric, first and second fluids, the first capillary tip is immersed in the dielectric fluid located close to the steady state interface, the dielectric fluid having a flow rate Q D ;
wherein the second capillary tip is located inside the first capillary tip and immersed in the dielectric fluid, such that upon flow of the dielectric, first and second fluids, the second conducting fluid flows through the second capillary against the dielectric fluid at a rate Q C , such that the steady state interface separating the dielectric fluid and the second conducting fluid is formed somewhere inside the first capillary tip;
wherein upon flow of the dielectric, first and second fluids, the first conducting fluid forms a steady capillary jet when conducting fluids are connected to a reference electrode;
wherein upon flow of the dielectric, first and second fluids, the spontaneous breakup of the capillary jet produces droplets of the first conducting fluid which move towards the fluid interface under the combined action of electric forces and drag exerted by the moving dielectric fluid; and
wherein upon flow of the dielectric, first and second fluids, the droplets release most of their electrical charge upon reaching the steady state interface, then exit the device through the annular gap.

9. An electro-fluidic method to produce emulsions and particle suspensions comprising:
immersion of a capillary in a dielectric fluid that flows along a micro-channel; said dielectric fluid being immiscible or poorly miscible with a first conducting fluid and a second conducting fluid; and wherein said second conducting fluid flows through a second capillary immersed in the dielectric fluid, an annular gap extending the length of the second capillary defined by the difference between the diameters of the micro-channel and the second capillary tip;
pumping counter-flow said second conducting fluid with respect to the dielectric fluid and forming a steady state interface; and
applying an appropriate electrical potential difference to said conducting fluids, producing a stream of charged droplets which move towards the steady state interface under the combined action of the electric and hydrodynamic forces;
wherein once the charged droplets reach the steady state interface they give up their charge and form a neutral emulsion that leaves through the annular gap.

10. The method according to claim 9 further comprising:
immersion of a number N of feeding tips (N≧1) in the first conducting fluid, such that a generic conducting fluid Li-th co-flows with the first conducting fluid at a flow rate Q i through the Ti-th tip (1≦i≦N); and
arranging the feeding tips such that L(i−1)-th conducting fluid surrounds the Ti-th tip.

11. The method according to claim 10 , wherein the diameters of the first and second capillary tips and the N feeding capillary tips are between 0.001 mm and 5 mm.

12. The method according to claim 10 , wherein the flow rate Q i-th of the fluid Li-th conducting fluid flowing through the feeding tip Ti-th is in the range between 10 −15 m 3 /s and 10 −7 m 3 /s; and
wherein the flow rate Q D of the dielectric fluid and the flow rate Q C of the second conducting fluid are both between 0 and 10 −1 m 3 /s.

13. The method

Assignees

• González-Loscertales Ignacio
• Gundabala Venkata Ramana
• Fernandes-Nieves Alberto
• Garcia Regina Gil
• Georgia Tech Res Inst
• Univ Sevilla
• Univ De Málaga

Inventors

• Ripoll Antonio Barrero
• González-Loscertales Ignacio
• Gundabala Venkata Ramana
• Fernandes-Nieves Alberto

Classifications

• B01F2215/0445

  Numerical electrical values, e.g. intensity, voltage · CPC title

• B01F13/0062

  Operations & Transport · mapped topic

• B01F13/0076

  Operations & Transport · mapped topic

• B01F2005/0034

  Operations & Transport · mapped topic

• B01F3/0815 Primary

  Operations & Transport · mapped topic