Scientists have developed an innovative technology that creates graphic images on transparent film using wrinkles without requiring pigments. This breakthrough is poised to revolutionize anti-counterfeiting measures and responsive display technology.
Ulsan National Institute of Science and Technology (UNIST) researchers announced a major scientific advancement on Thursday. A team led by Kim Tae Sung, a Department of Mechanical Engineering professor, has created a method for manipulating nanoscale wrinkles on transparent film to reveal or conceal color patterns reminiscent of traditional Korean ornamental designs.
The team’s discovery harnesses the principle of structural color, a phenomenon that occurs when light interacts with nanoscale structures. This principle allows chameleons and peacocks to display vibrant blue hues without blue pigment cells, thanks to nanoscale structures in their skin and feathers.
The team has achieved a remarkable technological feat by leveraging these nanoscale structures to create wrinkles. The wrinkles only materialize when the film is bent, allowing for dynamic color display or concealment. Furthermore, fine-tuning the spacing and height of these wrinkles can produce a wide spectrum of colors.
The researchers engineered a dual-layer film structure to ensure wrinkles only appear upon bending. When a rigid film is layered atop a flexible one, the disparity in physical properties causes nanoscale wrinkles to form on the rigid film’s surface when force is applied.
This mechanism mirrors the effect of pinching the skin on the back of your hand, where differences in elasticity between the epidermis and dermis create visible wrinkles. The team successfully created wrinkle pixels with varying spacings and heights on a single film using advanced dual photolithography techniques.
The wrinkles boast impressive dimensions, spacings from 800 to 2,400 nanometers (nm), and heights from 100 to 450 nanometers (nm). This versatility enables the technology to produce colors across the entire visible spectrum.
The team successfully patterned intricate traditional Korean decorative designs using these wrinkled pixels in a stunning demonstration. These patterns emerge only when the transparent film is bent and vanish when the pressure is released to reveal a transparent film.
Kim highlighted the importance of their work, stating, “Our technology enables the creation of dynamic structural colors through a straightforward process. Unlike conventional dye-based methods, our approach resists fading over time, making it highly competitive for anti-counterfeiting applications and interactive smart displays.”
The technology will be commercialized through a technology transfer agreement with NBS Technology Co., a leading domestic firm specializing in anti-counterfeiting solutions.
The study’s primary authors were UNIST researchers Kalyanan Tiyagarajan and Ji Sung-jun. The pioneering research was pre-published online on January 29 in the prestigious international journal Advanced Functional Materials and is slated for formal publication shortly.
The Korea Institute of Information and Communication Technology Planning and Evaluation and the National Research Foundation of Korea supported this cutting-edge research.