Thermo-Adaptive Block Copolymer Structural Color Electronics

Flexible electronics that enable the visualization of thermal energy have significant potential for various applications, such as thermal diagnosis, sensing and imaging, and displays. Thermo-adaptive flexible electronic devices based on thin 1D block copolymer (BCP) photonic crystal (PC) films with self-assembled periodic nanostructures are presented. By employing a thermo-responsive polymer/non-volatile hygroscopic ionic liquid (IL) blend on a BCP film, full visible structural colors (SCs) are developed because of the temperature-dependent expansion and contraction of one BCP domain via IL injection and release, respectively, as a function of temperature. Reversible SC control of the bi-layered BCP/IL polymer blend film from room temperature to 80 °C facilitates the development of various thermo-adaptive SC flexible electronic devices including pixel arrays of reflective-mode displays and capacitive sensing display. A flexible diagnostic thermal patch is demonstrated with the bi-layered BCP/IL polymer blend enabling the visualization of local heat sources from the human body to microelectronic circuits.     

Spray Synthesis of Photonic Crystal Based Automotive Coatings with Bright and Angular-Dependent Structural Colors

It is a challenge to prepare photonic crystal (PC) automotive coatings via spraying colloidal solutions because the fast fabrication tends to produce amorphous photonic crystals with faint colors. Here, a two-step spraying process followed by thermal curing is developed to prepare waterproof PC coatings with bright, uniform, and angular-dependent structural colors. The solvents in PC paint are studied to achieve a quick formation of liquid PC intermediate, which transformed into a highly crystalline PC coating. Thanks to the narrow and intense reflections, the as-made coatings present colors with high saturation, including the red/yellow/green/blue colors achieved by tuning the particle size, and many spectral/non-spectral colors via the mixing of base colors. Meanwhile, patterned or fully covered PC coatings with good chemical and mechanical stability can be prepared on different substrates, where the shiny colors changing with the viewing angles or the surface curvatures offer a new choice for personalized automotive coatings.