Fluorescence detection of mechanical damage

1. An autonomous self-indicating material comprising a plurality of microcapsules encapsulating a non-emissive solution, the solution comprising an aggregation-induced emission (AIE) luminogen and a solvent;

wherein the material is configured to be impacted by a sufficient force to damage it, and one or more microcapsules are ruptured, the non-emissive solution is configured to be released from ruptured microcapsules, the luminogen aggregates at or near the point of rupture, and the aggregated luminogen is emissive to autonomically self-indicate a location where damage has occurred in the material.

2. The material of claim 1 wherein the material comprises a polymer.

3. The material of claim 2 wherein the polymer comprises an epoxy resin, a polyurethane, polydimethylsiloxane, polyacrylic acid, polystyrene, bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, an aliphatic epoxy resin, a cycloaliphatic epoxy resin, a glycidylamine epoxy resin, a water-based epoxy resin, a bisphenol A diglycidyl ether (DGEBA) based resin, or a combination thereof.

4. The material of claim 1 wherein the microcapsules comprise about 1 weight percent to about 30 weight percent of the total weight of the material.

5. The material of claim 1 wherein the solvent comprises an (alkyl)acetate, an alcohol, an ether, an alkane, a ketone, a nitrile, water, an aromatic hydrocarbon, a protic solvent, an aprotic solvent, or a combination thereof.

6. The material of claim 1 wherein the solution comprises the luminogen at about 0.05 weight percent to about 20 weight percent.

7. The material of claim 1 wherein the microcapsules have a thermal stability up to about 400° C.

8. The material of claim 1 wherein the diameter of the microcapsules is about 200 nm to about 500 μm.

9. The material of claim 1 wherein the microcapsules have a shell-wall thickness of about 10 nm to about 50 μm.

10. The material of claim 1 wherein the microcapsules comprise a double-walled mixture of polyurethane and poly(ureaformaldehyde), or the microcapsules comprise a single-wall of polyurethane or poly(ureaformaldehyde).

11. A substrate comprising a coating of the material of claim 1 wherein the substrate comprises steel, aluminum, iron, zinc, copper, titanium, carbon, silica, a ceramic, cellulose, glass, a fiber, a polymer, or a combination thereof.

12. The substrate of claim 11 wherein the thickness of the coating is about 5 μm to about 10 mm.

13. The material of claim 1 wherein the luminogen is 1,1,2,2-tetraphenylethylene (TPE), fluorescein, hexaphenylsilole (HPS), 10,10′,11,11′-tetrahydro-5,5′-bidibenzo[a,d][7]annulenylidene (THBA), 9-(diphenylmethylene)-9 H-fluorene (DPMF), or 9, 10-Bis(p-dimethylaminostyryl)anthracene.

14. An autonomous self-indicating composite material comprising:

a vessel containing a non-emissive solution comprising an aggregation-induced emission (AIE) luminogen and a solvent;

a mixture of a polymer and a plurality of vessels; and

a substrate comprising a coating of the mixture;

wherein the composite material is configured to be impacted by a sufficient force to damage it, and one or more vessels are ruptured, the non-emissive solution is configured to be released from each ruptured vessel, the luminogen aggregates at or near the point of rupture, and the aggregated luminogen is emissive to autonomically self-indicate a location where damage has occurred in the composite material.

15. The composite material of claim 14 wherein the vessel is a substantially spheroid microcapsule encapsulating the solution, or the vessel has a microvascular structure comprising a hollow network of channels or fibers or capillaries, or a combination thereof, wherein the vessel is partially or substantially filled with the solution.

16. A method for preparing the autonomous self-indicating material of claim 1 comprising:

a) dissolving a luminogen in a solvent to form a non-emissive solution;

b) preparing microcapsules and encapsulating the non-emissive solution into the microcapsules;

c) mixing an epoxy resin or a polyurethane with the microcapsules to form the material; and;

d) coating the material onto a substrate.

17. A method for detecting damage to an autonomous self-indicating material, the method comprising:

a) irradiating an autonomous self-indicating material with ultraviolet light, wherein the material comprises a plurality of microcapsules encapsulating a non-emissive solution comprising an aggregation-induced emission (AIE) luminogen and a solvent;

wherein when the material is impacted by a sufficient force to damage it, one or more microcapsules are ruptured, the non-emissive solution is released from ruptured microcapsules, the luminogen aggregates at or near the point of rupture, and the aggregated luminogen is emissive to autonomically self-indicate a location where damage has occurred in the material; and

b) determining if a fluorescent signal is emitted by the luminogen;

wherein the absence of the fluorescent signal indicates that there is no damage to the material and the presence of the fluorescent signal autonomically self-indicates the location of damage to the material.

18. The method of claim 17 wherein composite is irradiated with ultraviolet light of about 365 nm.

19. The method of claim 17 wherein when the microcapsules are ruptured, the solvent is substantially removed from the point of rupture by evaporation, diffusion, absorption, adsorption, or a combination thereof.

20. The method of claim 19 wherein the solvent is substantially removed in less than about 24 hours.

21. A method for detecting damage to the autonomous self-indicating material of claim 1 comprising:

a) irradiating the material with ultraviolet light; and

b) determining if a fluorescent signal is emitted by the organic luminogen;

wherein the absence of the fluorescent signal indicates that there is no damage to the material and the presence of the fluorescent signal autonomically self-indicates the location of damage to the material.