Dendritic structures and tags

1. A method for generating a unique identifier, the method comprising:

providing a dendritic structure comprising a plurality of members extending away from a common point of the dendritic structure to form a stochastically branched arrangement of the members;

reading the dendritic structure to provide a signal; and

generating a unique identifier from the signal.

2. The method of claim 1 , wherein the dendritic structure is a dendritic metal structure.

3. The method of claim 2 , wherein the dendritic metal structure is formed by a method comprising:

providing an ion conductor, and two or more electrodes in contact with the ion conductor; and

applying a bias voltage across the electrodes,

wherein one of the electrodes forms an anode and another one of the electrodes forms a cathode; and

wherein the bias voltage is sufficient to grow the dendritic metal structure in or on the ion conductor extending from the cathode.

4. The method of claim 3 , wherein the dendritic metal structure incorporates a metallic component of the anode.

5. The method of claim 3 , wherein the ion conductor is in contact with a substrate.

6. The method of claim 1 , wherein the dendritic structure is disposed on a substrate comprising at least one of glass, plastic, metal, paper, fabric, an electrical insulator, and a semiconductor.

7. The method of claim 1 , wherein the dendritic structure is disposed on a substrate that comprises a flexible material.

8. The method of claim 1 , wherein the dendritic structure is supported on a substrate, and wherein a barrier layer is disposed between the dendritic structure and the substrate.

9. The method of claim 1 , wherein the dendritic structure is in contact with an ion conductor during the reading of the dendritic structure.

10. The method of claim 1 , wherein reading the dendritic structure comprises optically reading the dendritic structure using a camera or an array of photodetectors capable of recognizing the dendritic structure with light.

11. The method of claim 1 , wherein reading the dendritic structure is performed electrically.

12. The method of claim 11 , wherein the dendritic structure is read by capacitance, the method comprising:

contacting the dendritic structure with a plurality of sensors, and

measuring capacitance at each sensor.

13. The method of claim 11 , wherein the dendritic structure is read by resistance, the method comprising:

electrically contacting the dendritic structure with a plurality of sensors, and

measuring resistance at each sensor.

14. The method of claim 1 , wherein reading the dendritic structure is performed using X-ray fluorescence spectroscopy.

15. The method of claim 1 , wherein reading the dendritic structure is performed using a radio frequency identification scheme, the method further comprising:

illuminating the dendritic structure with radio waves of different frequencies; and

detecting one or more frequencies of the reflected radio waves.

16. The method of claim 1 , wherein generating a unique identifier comprises:

applying a numerical method to the signal provided by the reading of the dendritic structure; and

generating a unique identifier from the numerical method.

17. A method for generating a unique identifier, the method comprising:

providing a dendritic structure comprising a plurality of members extending away from a common point of the dendritic structure to form a stochastically branched arrangement of the members;

reading the dendritic structure electrically to provide a signal; and

generating a unique identifier from the signal.

18. The method of claim 1 , wherein the unique identifier is used to mark an object.

19. The method of claim 18 , wherein the identification of the object is used to track a location of the object.

20. A method, comprising:

reading a dendritic structure that forms part of an object to provide a signal, the dendritic structure comprising a plurality of members extending away from a common point of the dendritic structure to form a stochastically branched arrangement of the members;

generating a unique identifier from the signal; and

performing at least one of:

identifying the object using the unique identifier;

authenticating the object using the unique identifier;

using the unique identifier as a key in the encryption of data; and

using the unique identifier as a key to access encrypted data.