Mechanical self-assembly fabrication of gears

Self-assembled buckling of thin film/substrate systems has attracted increasing attention for fabricating ordered micro- and nanostructures. However, most studies have been limited to a planar substrate. We employ the spontaneous buckling patterns on curved substrates to fabricate several types of quasi-two-dimensional (quasi-2D) and three-dimensional (3D) gear-like microcomponents. The substrate curvature can be positive or negative, and the proposed technique does not require extra external guidance or a prepatterned template. The gear features, including the number and amplitude of the teeth, can be manipulated by controlling the geometry and material properties of the film/substrate system. A theoretical model is established to predict the buckled profiles, which is validated by numerical simulation and experiment. A variety of gear morphologies, including 3D bevel and helical gears (which are difficult to fabricate using the conventional photolithography/etching technique), are obtained to further demonstrate the potential of the mechanical self-assembly approach.