Magnetic DNA Origami Nanorotors.

Self-assembled DNA nanostructures show great promise as functional devices, highly configurable materials, and in nanorobotics. Magnetic control provides a powerful and broadly applicable actuation mechanism due to its programmability, compatibility with biological entities, and orthogonality to chemical or electrical stimuli. Here we demonstrate magnetic nanoactuators by leveraging the unique site-specificity of DNA origami to assemble magnetic nanocubes with high magnetization and magnetic anisotropy on high-aspect ratio DNA origami bundles. We trace and control 100s of our DNA origami nanorotors at the single-rotor level and demonstrate their magnetic clamping and controlled rotation under uniform and rotating magnetic fields. By varying the population and inter-particle spacing of the nanocubes, magnetic torque values on the order of 10-100 pN nm are calculated at field strengths < 10 mT. Monte Carlo simulations reveal that the assembly of nanocubes on DNA origami rotors leads to collective magnetic properties, with numerically estimated torque values in good agreement with the experiments. Our work demonstrates a proof-of-concept of nanoscale magnetic actuators for potential uses as programmable torque nano-probes and in nanorobotics.