Guangdong pc lens manufacturer--the research team of Zhejiang University develops codeable plastics
The research group of Professor Tao Xie from Zhejiang University proposed a method of precise 'encoding' in plastic products, through digital control of the internal 'stress' of plastic products, and implanting exquisite 'invisible' patterns to realize the invisible storage of information. Related papers were published online in the journal Nature Communications recently. Zhang Guogao, the first author of the paper and a doctoral student at Zhejiang University, showed reporters several coin-sized transparent plastic sheets. Under the polarized lenses, these transparent plastic sheets clearly showed patterns such as QR codes, colorful butterflies, Mona Lisa portraits, etc. . 'We did not add pigments to the material, nor did we change the microstructure of the surface of the material. The pattern is due to stress.' Zhang Guogao said that stress is brought in by process and is an inevitable ubiquity in plastic products. It will be released in the form of warping, deformation, or even cracking, which is one of the reasons why plastic products are not durable. Because of the existence of stress, the refractive index in each direction inside the transparent material is different. Under the polarized lens, the inside of the plastic product will show colorful colors. The research team has found a way to digitally control stress. The researchers first stretched a polymer plastic film uniformly at about 60 degrees Celsius to store the stress, and then used a laser printer to print different gray-scale patterns on the polymer film, and irradiated it with infrared light to fix points on the plain film. 'stress. The difference in temperature makes the degree of stress release of each pixel point different, so the stress presents a fine gradient change. In this way, the pattern is 'transcoded' from the grayscale to the stress distribution, and then a preset 'invisible' pattern is formed in the material. 'In materials, stress is usually a passively introduced and uncontrollable factor. We control this force and perform'encoding' operations to produce more functions.' Xie Tao said, the first one to be seen The application is to realize the invisible storage of information. 'Only with the help of polarized lenses can we see the patterns stored in the material.' Zhang Guogao believes that stress is related to the optical properties, electrical properties and structure of the material. By 'coding' stress, programmable plastics will exhibit more functions. 'For example, all 3D printing nowadays is from liquid material to solid, our method provides a possibility of going from solid to solid.'