Bio-inspired Janus structural color films as visually flexible electronics

Multifunctional composite flexible sensors are essential components in flexible and stretchable electronics. In this paper, we present novel mussel-inspired Janus structural color films as visually flexible electronics. The Janus composite film with a three-layer structure, which is compozed of a conductive carbon nanotube (CNT) layer, a supporting polydimethylsiloxane (PDMS) layer and a structural color layer formed by two-dimensional colloidal crystals (2D-CCs), is prepared by a hierarchical assembly strategy. The manufactured multi-layer CNT films and the 2D-CCs are integrated on both sides of the supporting PDMS layer, respectively by the self-assembly process and the adhesion of polydopamine (PDA) to provide corresponding excellent conductivity, flexibility and visual optical sensing for the Janus composite film. It is demonstrated that the CNT films could not only increaze the contrast of structural color of the 2D-CC array as their light absorption characteristics in the broadband frequency field, but also impart the composite film with photothermal response characteristics. In addition, because of the outstanding electrical properties, visualized structural color and photothermal response, the resulting Janus structural color films show stable electrical sensing and visualized color-sensing under deformations arose by human motions and near-infrared (NIR) illumination, which could play essential roles in flexible and stretchable electronics.