Vein identification technique
View Patent ↗A technique for identifying a vein in a patient is disclosed. The technique involves the application of a thermochromic ink to a venous area on the skin of a patient (e.g., human or animal). The thermochromic ink comprises thermosensitive color-changing microcapsules that contain a proton-accepting chromogen and a desensitizer. The desensitizer possesses a melting point above which the chromogen is capable of becoming protonated, thereby resulting in a color change. Thereafter, the venous area is observed for the color change.
1. A method for identifying a vein in a patient, the method comprising:
placing a thermochromic ink in direct contact with a venous area on the skin of a patient, wherein the thermochromic ink comprises thermosensitive color-changing microcapsules that contain a proton-accepting chromogen and a desensitizer, wherein the desensitizer possesses a melting point above which the chromogen is capable of becoming protonated, thereby resulting in a color change; and
thereafter, observing the venous area for the color change.
2. The method of claim 1 , wherein the proton-accepting chromogen is a leuco dye.
3. The method of claim 2 , wherein the leuco dye includes a phthalide, phthalene, acyl-leucomethylene, fluorane, spiropyrane, cumarin, or a combination thereof.
4. The method of claim 1 , wherein proton-accepting chromogens constitute from about 0.1 wt.% to about 20 wt.% of the microcapsules.
5. The method of claim 1 , wherein the desensitizer has a boiling point of about 150° C. or higher.
6. The method of claim 1 , wherein the desensitizer has a melting point of about from about 26° C. to about 34° C.
7. The method of claim 1 , wherein the desensitizer includes a saturated or unsaturated alcohol, an ester of a saturated or unsaturated alcohol, an amide, or a combination thereof.
8. The method of claim 1 , wherein desensitizers constitute from about 10 wt. % to about 70 wt. % of the microcapsules.
9. The method of claim 1 , wherein the microcapsules further comprises a proton-donating agent.
10. The method of claim 9 , wherein proton-donating agents constitute from about 0.5 wt. % to about 30 wt. % of the microcapsules.
11. The method of claim 1 , wherein the microcapsules are formed from a polymer resin.
12. The method of claim 11 , wherein polymer resins constitute from about 20 wt. % to about 80 wt. % of the microcapsules.
13. The method of claim 1 , wherein the microcapsules having a mean particle size of from 10 nanometers to about 10 micrometers.
14. The method of claim 1 , wherein the chromogen undergoes a color change at a temperature of from about 26° C. to about 34° C.
15. The method of claim 1 , wherein the chromogen undergoes a color change at a temperature of from about 28° C. to about 33° C.
16. The method of claim 1 , wherein the thermochromic ink further comprises a cooling agent.
17. The method of claim 16 , wherein the cooling agent has an enthalpy of vaporization of about 40 kilojoules per mole or less.
18. The method of claim 16 , wherein the cooling agent is an alcohol.
19. The method of claim 16 , wherein cooling agents constitute from about 50 wt. % to about 99.9 wt. % of the ink and the microcapsules constitute from about 0.1 wt.% to about 50 wt. % of the ink.
20. The method of claim 16 , wherein cooling agents constitute from about 30 wt. % to about 99 wt. % of the ink and the microcapsules constitute from about 1 wt. % to about 70 wt. % of the ink.
21. The method of claim 1 , wherein the thermochromic ink is disposed on a substrate.
22. The method of claim 21 , wherein the substrate contains a nonwoven web.