| There is a considerable interest in developing bioactive papers with active recognition and/or functional capabilities. Despite their distinct portability and practicability, direct sensing or recognition platform are often restricted to precisely aligned components or specific reactions. Motivated by photonic band gap materials, a non-specific color can be obtained by controlling ordered structures and further applied as an optical indicator for biosensing. In this work, polymerized colloidal crystal arrays (PCCAs) were for the first time integrated with a paper support. Since the continuous hydrogel phase can change and recover its volume by reversible hydration, the accompanying change in crystal lattice spacing imparts a visible color change due to Bragg diffraction. This material also possesses excellent salt anti-interference, extended cycling performance, and robust mechanical properties. Compared to other rigid substrates, only PCCAs on paper exhibit significant color change between the dry and hydrated states. These characteristics make paper-based polymerized colloidal crystal arrays (PB-PCCAs) promising for a new generation of sensing and anti-falsification applications. A future challenge is to develop optical changes that correspond to specific molecular recognition, perhaps by decorating the hydrogel or particles with functional groups. |
