Switchable Curvotaxis in Graphene via Torsion-Strain Coupling

We present a minimal, purely mechanical strategy for programmable nanoscale transport based on curvature-mediated energetics (curvotaxis). A prestrained graphene ribbon subjected to torsion undergoes a buckling transition that reconstructs its curvature landscape, thereby driving an adsorbed flake across a critical curvature separating two transport regimes. Below this threshold (prebuckling), adhesion dominates, promoting center-seeking migration; above it (postbuckling), bending elasticity prevails, favoring edgeward motion. An analytical energy model captures this competition and identifies the critical curvature governing this reversible switching. By applying cyclic torsion or cyclic axial strain under fixed torsion, reversible wrinkle formation and annihilation enable deterministic, bidirectional flake transport. Torsion-strain coupling therefore functions as a simple and controllable mechanical mechanism for field-free, programmable motion at the nanoscale.