Rapid and Reversible Shape Memory Effect in Colloidal Crystals Engineered with DNA

Mechanically responsive crystals, which exhibit reversible, rapid, and complex dynamics, are essential to the development of flexible electronics, artificial muscles, and various dynamic components in soft robotics. However, due to the limited flexibility of atomic bonds, only a small number of reversible deformation modes have been realized for these materials. Colloidal crystals engineered with DNA represent an ideal platform for the development of mechanically responsive crystals, owing to the stimuli-responsiveness and high fidelity of the DNA bonds that define the crystal. Herein, we report the reversible mechanical responsiveness of colloidal crystals engineered with DNA to deformations typically considered irrecoverable in conventional molecular and atomic crystals. These advances were obtained through the synthesis of large (>100 µm) single crystals, which enable previously unrealizable characterization techniques including in-situ optical microscopy and single-crystal x-ray diffraction. These techniques shed light into both the unprecedented nature of the macroscale deformation and recovery as well as the resilient and flexible internal structure of the single crystals. Since single crystals are the basis for many optical and electronic device components, the synthetic methods and crystal deformation capabilities described in this work lay the foundation for the realization of advanced structural materials for applications such as optics, chemical sensing, and many others which require the properties of both soft and crystalline materials.