Introduction

The invention concerns the creation of microspheres that are observed with an optical microscope and that exhibit a fingerprint-like structure. Each microsphere has a different imprint that is generated in a completely random manner and therefore it is impossible to duplicate. These microspheres are an example of a PUF (Physical Unclonable Functions) key and can be used to create non-clonable labels

Technical features

The invention is based on the use of cholesteric liquid crystals as a means for the creation of random self-assembling structures on a micrometric scale. These microspheres are confined to an amorphous matrix and an electric field of appropriate frequency and intensity is applied to them. The liquid crystal molecules reorient themselves due to the electric field leading to the creation of the fingerprint texture. The amorphous matrix can contain different types of microspheres, each of them can, for example, be prepared using a different fluorescent material capable of emitting, under suitable lighting conditions, fluorescence light on established wavelength ranges, increasing the complexity of the system. Compared to the PUF keys based on fingerprint textures present in the literature, this anti-counterfeiting device has a higher configuration level.

Possible Applications

• As anti-counterfeiting devices;
• Identification of documents (passports, IC, driving licenses);
• Authentication of commercial products such as jewelry or watches;
• Protection of foods or commonly used products such as tobacco and clothing (if the individual microspheres or agglomerates are enclosed in films made of biocompatible materials and suitable for packaging).

Advantages

• Configurable security level;
• The production process is simple and low cost;
• Being of sub-millimeter size, they are difficult to detect with the naked eye and can be easily hidden inside and outside an object;
• The decoding process is adaptable to the specifications of the various detection means.