Preparation And Application Of Diamond Based Flexible Physical Unclonable Function Label

Fake and shoddy products have always been a particularly important challenge that people face,and this will disturb normal order of market economy.Inferior products not only violate intellectual property rights,but also endanger human financial and physical safety.The property losses caused by counterfeit products are untold every year.In addition,the sale of counterfeit drugs directly causes harm to people health.An effective solution is to add special tags on products that need to be protected,phosphorescence and fluorescence anti-counterfeiting techniques have been developed in our previous work.However,this anti-counterfeiting methods are easy to be cracked,and other technologies also face many challenges and defects,such as insufficient technical proof to prevent effective attacks and high cost.Physical unclonable functions(PUFs)have been developed as a reliable authentication and anti-counterfeiting systems,which have been wildly applied in the field of anti-counterfeiting.PUF as an unclonable element is a physical way to simulate the function of a single function,and PUFs are designed to be unforgeable due to the natural randomness.Usually,for each PUF,one input such as optical or electrical excitation(“Challenge”)corresponds to one output(“Response”),this process is called a challenge-response pair(CRP),which is used to verify the authenticity of PUF.Since the concept of PUF was proposed in 2002,PUF has been extensively studied by researchers in nearly 20 years.PUFs can be divided into two categories: silicon-based PUF and non-silicon-based PUF.Silicon-based PUF has limited application scenarios due to the process of contact excitation and response.Optical PUFs,as a typical example of non-silicon PUFs,have been caused widely attentions,which have been applied for different scenarios due to the non-contact and fast optical reading.However,most of the optical PUFs are rigid and not have good biocompatibility and flexible,which cannot be applied for products with complex surface,and thus limiting their application.The special structure of diamond makes it withstand most of solvents such as strong acid and alkali,and diamond also is a kind of semiconductor materials with excellent biocompatibility.Therefore,using materials such as micro-diamond to develop a kind of biocompatibility and flexible PUFs with high stability and anti-counterfeiting ability expand their application scenario.In this work,flexible PUF labels have been demonstrated by embedding microdiamonds into silk fibroin films,which can be applied for objects with complex shapes.The flexibility of silk fibroin films,the extremely high stability and random distribution of the micro-diamond ensures the performance of PUFs,and the maximum encoding capability of 210000 is finally realized.The safety performance analysis results also verify the biosafety of the PUF system.The flexible PUFs have been applied in polyethylene material,and human skin,and even have been implanted under chicken skin tissue.(1)The flexible PUF label have been fabricated by imbedding micro-diamonds into silk fibroin membranes.Micro-diamonds were added into aqueous solution of fibroin under magnetic stir to form the uniform mixture,and then dropped onto the surface of pretreated substrate to form a randomly distributed film through spin coating and water bath annealing.Laser is used as input challenge of the PUF label and the output is presented in the form of Raman signals of micro-diamond,and then the Raman signals were transformed into digitized keys.(2)In order to ensure the practical application ability of diamond-based flexible PUF labels,the flexibility of the PUF label was demonstrated.The PUF label was attached to surface of a flexible substrate,and a bending test of the PUF label was performed.The PUF label can keep its original shape after 3600 times of bending test with bending amplitude of 40%.In addition,the as-prepared PUF labels have been attached onto the surface of polyethylene material,and human skin,and even have been implanted under chicken skin tissue,promising their practical applications.