Microchiral pinwheel arrays based on achiral molecules

From a molecular perspective, chirality is manifested in the intrinsic asymmetry of atomic arrangements that cannot be superimposed on their mirror images. Achiral molecules at nanometer scale can be assembled to have micron-scale chiral structures using physical stimuli, but the resulting chiral structures are often spatially limited, difficult to control over large areas, or unstable once the stimulus is removed. Here we show that a confined anisotropic molecular medium, derived from the nematic mesophase, undergoes a field-driven symmetry-breaking transition that generates micron-scale chiral structures. This approach provides a simple and scalable route to generate macroscopic chiral optical materials from molecularly symmetric precursors.