Optical electrowetting device
The invention relates to an optical electrowetting device comprising a conductive fluid ( 5; 101 ) and a non-conductive fluid ( 4; 102 ), said fluids being non miscible, and an insulating substrate ( 2; 103 ) on which both fluids are in contact and form a triple interface, wherein the natural contact angle ( 105 ) of the non-conductive fluid ( 102 ) on the substrate ( 103 ) in presence of the conductive fluid ( 101 ) is comprised between 0° and about 20°. This device may be a variable focus liquid lens, an optical diaphragm, an optical zoom. The invention further relates to an apparatus such as a camera, a cell phone, an endoscope or a dental video camera, comprising said electrowetting device and a driver or electronic means for controlling the lens.
1. An optical electrowetting device comprising a conductive fluid and a non-conductive fluid, said fluids being non miscible, and a planar insulating substrate on which both fluids are in contact and form a triple interface, wherein the natural contact angle of the non-conductive fluid on the planar insulating substrate in presence of the conductive fluid, through the non-conductive fluid, is comprised between 0° and 20°, and wherein the planar insulating substrate has a surface energy above 30 mN/m and the non-conductive fluid contains a compound of surface tension equal to or above 28 mN/m.
2. The optical electrowetting device of claim 1 , wherein the natural contact angle is comprised between 5° and 16°.
3. The optical electrowetting device of claim 1 , wherein the natural contact angle θ n is such that 0°≦θ n ≦20° over a range of temperatures comprised between −20° C. and +70° C.
4. The optical electrowetting device of claim 1 , wherein the difference d st between the surface tension of the non-conductive fluid and the surface energy of the planar insulating substrate is within the range −15<d st <+15 mN/m.
5. The optical electrowetting device of claim 1 , wherein the planar insulating substrate surface energy has a polar component comprised between 0 mN/m and 2 mN/m.
6. The optical electrowetting device of claim 1 , wherein the planar insulating substrate is made of, or comprises an upper layer which is made of, a para-xylylene linear polymer or an aromatic vinylsiloxane polymer.
7. The optical electrowetting device of claim 6 , wherein the planar insulating substrate is made of, or comprises an upper layer which is made of one of Parylene C, Parylene D, Parylene N, Parylene F, Parylene AF-4, or Parylene VT-4.
8. The optical electrowetting device of claim 6 , wherein the planar insulating substrate is made of, or comprises an upper layer which is made of, divinylsiloxane-benzocyclobutene (DVS-BCB) polymer.
9. The optical electrowetting device of claim 1 , wherein the whole of the non-conductive and the conductive fluids has a mean arithmetic cinematic viscosity of between 1.5 cSt and 40 cSt, within a temperature range of −10° C. to +60° C.
10. The optical electrowetting device of claim 1 , wherein the planar insulating substrate is made of, or comprises an upper layer which is made of, a para-xylylene linear polymer, the conductive fluid comprises water and an organic or inorganic salt, and the non-conductive fluid comprises halogenated alkane(s) and/or siloxane oil(s).
11. The optical electrowetting device of claim 10 , wherein the planar insulating substrate is made of, or comprises an upper layer which is made of, Parylene C, the conductive fluid comprises water and an inorganic salt, and the non-conductive fluid comprises halogenated alkane(s) and siloxane oil(s).
12. The optical electrowetting device of claim 11 , comprising:
a planar insulating substrate made of, or comprising an upper layer made of, Parylene C;
a conductive fluid comprising:
i) from 35 weight % to 45 weight % of water,
ii) from 0.15 weight % to 0.25 weight % of sodium sulphate,
iii) from 55 weight % to 65 weight % of monopropylene glycol (MPG); and
a non-conductive fluid comprising:
a) from 15 weight % to 25 weight % of phenyltris (trimethylsiloxy) silane,
b) from 55 weight % to 65 weight % of a cyclosiloxane and phenylated siloxane mixture having a Ph/Si ratio less than 1.33 and a Ph/Me ratio less than 1.33,
c) from 15 weight % to 25 weight % of 1,8-dichlorooctane, and
d) from 0.4 weight % to 0.8 weight % of a butylated hydroxyl toluene.
13. The optical electrowetting device of claim 1 , which is one of a variable focus liquid lens, an optical diaphragm, or an optical zoom.
14. An apparatus comprising an optical electrowetting device according to claim 13 , and a driver or electronic means for controlling the interface.
15. The apparatus of claim 14 , wherein the driver or electronic means further comprises means to apply an A.C. voltage to the conductive fluid.
16. The apparatus of claim 15 , which is one of a camera, a cell phone, a telemeter, an endoscope, or a dental video camera.
17. The optical electrowetting device of claim 10 , wherein the planar insulating substrate is made of, or comprises an upper layer which is made of, one of Parylene C, Parylene D, Parylene N, Parylene F, Parylene AF-4, or Parylene VT-4.
18. The optical electrowetting device of claim 12 , further comprising a biocide agent up to 0.2%.