Acidichromic organic crystals with manifold mechanical deformations for reconfigurable flexible optical tuner

Acicular organic crystals with micro- or centimeter scale in length have been widely employed as media for transducing self-emitted or inputted optical signals, i.e., active or passive optical waveguides. Combining the emerging dynamic adaptability of crystals with optical waveguides, provides an unprecedented opportunity to development of crystal-based organic flexible optoelectronics devices. Here, we report a Schiff base crystal that combines two unique features of integrated elastic-bending, plastic-twisting, acid-bending deformations and protonation-induced crystal acidichromism. The emission color of a single crystal can be selectively and reversibly regulated at different locations between green (554 nm) and deep red (659 nm) by protonic acid vapor fuming, producing various block heterojunction structures easily identified by color and emission. In addition, the flexible heterojunction structures can be reconfigured by a quickly repeated erasing-writing process based on reversible protonation-deprotonation. Making full use of the integrated flexibilities, acidichromic and optical waveguides properties of crystals, a flexible optical crystalline tuner with a wide range of output signals that can be adjusted flexibly was further constructed. These results not only demonstrate that reconfigurable optical structures can be designed using organic crystals, but also open prospects for the application of flexible organic crystals in lightweight, wearable electronic devices.