Devices and methods for sorting droplets by surface tension

Patent metadata

Field	Value
Publication number	US-9823174-B2
Application number	US-201715443620-A
Country	US
Kind code	B2
Filing date	Feb 27, 2017
Priority date	Nov 19, 2015
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

A tunable superomniphobic surface with flower-like TiO 2 nanostructures was fabricated into a device with precisely tailored surface energy domains that can sort droplets by surface tension. This apparatus and method for droplet sorting will enable inexpensive and energy-efficient analytical devices for personalized point-of-care diagnostic platforms, lab-on-a-chip systems, fuel sensor applications, biochemical assays and biosensors.

First claim

What is claimed is:

1. An apparatus for analyzing a property of a liquid, the apparatus comprising:
a surface comprising superomniphobic and omniphobic areas, the surface having a first end and a distal end, and a gradient of two or more domains, each domain occupying different positions on the surface, wherein the superomniphobic and omniphobic areas comprise TiO 2 nano-flower three-dimensional structures that establish a re-entrant texture on the surface,
wherein a first domain is at the first end and each other domain has an increased surface energy relative to the domain immediately preceding it; and
wherein when a liquid droplet is placed on the first domain, having the lowest surface energy, and the surface is inclined relative to horizontal, the droplet traverses part or all of one or more of the domains and the domain where the droplet comes to the rest is indicative of the surface tension of the liquid.

2. The apparatus of claim 1 wherein the first end is at the top of an incline having a slope toward the distal end.

3. The apparatus of claim 1 wherein the longitudinal width of each domain is about 0.5 mm to about 10 cm.

4. The apparatus of claim 1 wherein the TiO 2 structures are surface modified with a fluoroalkyl silane.

5. An apparatus for comprising:
a titanium metal sheet having a first end and a distal end, and a layer of a TiO 2 nano-flower three-dimensional structure having a re-entrant surface texture wherein the TiO 2 is surface modified with a fluoroalkyl silane and the surface modified TiO 2 nano-flower structures form a superomniphobic surface on the sheet; and
the surface comprises a gradient of two or more domains from the first end to the distal end; wherein
the domains occupy different positions on the sheet and are ordered in increasing surface energy, the first end of the sheet having the lowest surface energy, the distal end of the sheet having the highest surface energy, and each of the second or more domains have increased surface energy relative to the domain immediately preceding it;
the first domain comprises the superomniphobic surface and each of the second or more domains comprise omniphobic areas having less than superomniphobicity; and
the width of each domain is about 0.1 cm to about 10 cm.

6. The apparatus of claim 5 wherein when a liquid droplet is placed at the first end closest to the lowest surface energy domain of the gradient and the surface is inclined relative to horizontal, the droplet traverses part or all of one or more of the domains and the domain where the droplet comes to the rest is indicative of the surface tension of the liquid.

7. The apparatus of claim 6 wherein the difference in surface energy between each adjacent domain is less than about 20 mN/m, and the difference in surface energy between at least two or more adjacent domains is less than 10 mN/m.

8. A method for analyzing a property of a liquid, the method comprising:
a) placing a liquid droplet on an apparatus comprising:
i) a surface comprising superomniphobic and omniphobic areas, the surface having a first end and a distal end, the first end at the top of an incline and having a slope toward the distal end; and
ii) the surface comprises a gradient of two or more domains, each domain occupying different positions on the surface, wherein the first domain, having the lowest surface energy, is closest to the first end and each of the second or more domains have an increased surface energy relative to the domain immediately preceding it;
wherein when the droplet is placed at the first end, the droplet traverses part or all of one or more of the domains; and

b) determining the final position of the droplet;

wherein the domain where the droplet comes to the rest is indicative of the surface tension of the liquid.

9. The method of claim 8 wherein when the roll off angle of the droplet is lower than the tilt angle of the incline of a particular domain, the droplet rolls off the domain, and if the roll off angle is higher than the tilt angle of the incline of a particular domain, the droplet remains on the domain.

10. The method of claim 8 wherein the superomniphobic and omniphobic areas comprise TiO 2 nano-flower three-dimensional structures that establish a re-entrant texture on the surface, wherein the TiO 2 structures are surface modified with a fluoroalkyl silane.

11. The method of claim 8 wherein each of the second or more domains surfaces have been modified with, for example, ultraviolet irradiation, plasma, or chemicals, to increase the surface energy of the domains, wherein increasing the surface modification provides a domain having increased surface energy.

12. The method of claim 8 wherein the difference in surface energy between each adjacent domain is less than about 20 mN/m.

13. The method of claim 8 wherein the volume of the droplet is about 0.1 μL to about 200 μL.

14. The method of claim 8 wherein the diameter of the droplet is about 0.1 mm to about 4 mm.

15. The method of claim 8 wherein the liquid is a pure compound or the liquid comprises a mixture of two or more components, wherein liquids of different compositions achieve different final positions, thereby indicating their different compositions relative to each other.

16. The method of claim 8 wherein the droplet comprises aqueous ethanol, a fuel mixture, a mixture of gasoline and kerosene, a mixture of diesel and kerosene, diesel, gasoline, biofluids, blood, or urine.

17. The method of claim 8 wherein the apparatus comprises two to about 100 domains.

18. The method of claim 8 wherein the surface energy of each one of the domains has been tuned by irradiating the domain with a 254 nm ultraviolet lamp wherein the distance between the ultraviolet lamp and the domain is about 2 cm and the irradiation time is from 10 seconds to 60 minutes.

19. The method of claim 18 wherein the irradiation is carried out for 10 seconds to 10 minutes.

20. The method of claim 8 wherein the incline has a tilt angle of about 0.5° to about 75°, relative to horizontal.

21. The method of claim 20 wherein the tilt angle is about 15°.

22. The method of claim 8 wherein the method is carried out with two or more droplets, optionally with different compositions, the method further comprising sorting each droplet by its final position where the final position is indicative of each droplet's composition or indicative of each droplet's surface tension.

23. The method of claim 22 wherein the apparatus comprises two or more surfaces at different angles.

24. A method for analyzing a property of a liquid, the method comprising:
a) placing one or more liquid droplets on an apparatus comprising:
one or more individual surfaces comprising superomniphobic and omniphobic areas, each surface having a first end and a distal end, the first end of each individual surface at the top of an incline and having a slope toward the distal end;
wherein each of two or more individual surfaces have a different surface energy and a different tilt angle, or each of two or more individual surfaces have about the same surface energy and a different tilt angle,
wherein
when the droplet is placed at the first end of a surface, the droplet traverses part or all of one or more of the domains of the surface; or
when the droplet is placed at the first end of a surface, the droplet traverses part or all of one individual surface having a fixed surface energy wherein the tilt

Assignees

• Univ Colorado State Res Found

Inventors

• Kota Arun K
• MOVAFAGHI Sanli
• Jathar Shantanu

Classifications

• G01N33/22 Primary

  Fuels; Explosives · CPC title

• G01N21/33

  using ultraviolet light (G01N21/39 takes precedence) · CPC title

• G01N13/02 Primary

  Investigating surface tension of liquids · CPC title