Roll-to-Roll Optical Manufacture of Mechano-Responsive Photonic Sheets

Dynamic optical appearance plays a critical role for many animals that rely on adaptive camouflage or bright and varying color displays for their survival. The photonic materials used by these organisms are not just of interest to biologists, but have also captured the imagination of physicists, chemists, materials scientists, and engineers, who are trying to emulate their dynamic optical behavior in synthetic bio-inspired material systems. Mechanically-responsive soft photonic materials, which change their optical properties in response to mechanical forces, represent a versatile material platform for colorimetric force sensing in a variety of different research and technology fields, including healthcare, robotics, and human-computer interaction. Existing micro and nanofabrication approaches are varied, including self-assembly of colloids or liquid crystals, magnetically induced self-assembly, block copolymer self-assembly, sequential spin coating, and laser writing and interference lithography. However, the application of these materials has been limited by drawbacks relating to their optical quality, mechanical properties, limited scalability, or cost and complexity of manufacture.<br/>We have developed a roll-to-roll manufacturing technique based on our recent progress in combining Lippmann photography with holographic recording materials, providing a fast, scalable, low-cost method of producing mechano-responsive photonic sheets. This essentially allows us to optically print elastic, three-dimensional photonic structures in a single step, across macroscopically-sized areas, using an incoherent light source. The benefits of this technique include high-resolution spatial patterning across the entire RGB color space, as well as printing in the near-infrared region to create hidden patterns that appear when stretched. We can also tune the angular distribution of reflected light, resulting in materials with specular, isotropic diffuse, or anisotropic diffuse reflection, as well as tuning the mechanical properties of the material to map the color change to a variety of different force ranges. Finally, we can integrate these materials with different textiles, enabling applications in fashion and healthcare.