HC Plastics News: Professor Xie Tao from Zhejiang University proposed a method of accurately “encoding†in plastic products. By digitally regulating the internal “stress†of plastic products, implanted a delicate “invisible†pattern to realize the invisible storage of information. Related papers were published online in the journal Nature Communications. Zhang Guogao, the first author of the paper and a doctoral student at Zhejiang University, showed the reporter a few coin-sized transparent plastic sheets. Under the polarized lenses, these transparent plastic sheets clearly showed the two-dimensional code, colored butterflies, Mona Lisa portraits and other patterns. . “We didn’t add pigment to the material, nor did it 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 reasons and is an inevitable ubiquity in plastic products. It is released in the form of warpage, deformation, and even cracking, which is one of the reasons why plastic products are not durable. Because of the presence of stress, the refractive indices in various directions inside the transparent material are different. Under the polarized lens, the interior of the plastic product will show a colorful color. The group found a way to digitally control stress. The researchers first uniformly stretched a polymer plastic film at a temperature of about 60 degrees Celsius to store the stress. Then, a laser printer printed a pattern of different gray scales on the polymer film, and irradiated with infrared light to "spot" on the plain film. "stress. The difference in temperature causes the degree of stress release at each pixel to be different, so the stress exhibits a fine gradient change. In this way, the pattern is "transcoded" from the grayscale into a stress distribution, which in turn forms a predetermined "invisible" pattern in the material. “In materials, stress is usually a passively introduced, uncontrollable factor. And we control this force and perform 'encoding' operations to produce more functions.†Xie Tao said that the first one is visible. The application is to achieve the invisible storage of information. “Only by means of polarized lenses, we can see the pattern of material storage.†Zhang Guogao believes that stress is related to the optical properties, electrical properties and structure of materials. By "coding" stress, programmable plastics will show more functionality. “For example, all 3D printing today is from liquid materials to solids, and our approach offers a possibility from solid to solid.†Editor in charge: Yao Chunlin Flanged Pneumatic Angle Seat Valve WENZHOU FOREVER CLASSIC TECHNOLOGY CO.,LTD , https://www.fballvalve.com