The size-dependent elasticity of a series of nickel cantilever microbeams was investigated experimentally for the first time. The experimental results revealed that the dimensionless natural frequencies of the cantilever microbeams increase to about 2.1 times with the beam thickness decreasing from 15 to 2.1 $\mathrm{\mu }\text{m}$ . Furthermore, based on the strain gradient elasticity theory (SGT) and by using the differential quadrature method (DQM) and the least square method (LSM), the experimental results were interpreted and the material length scale parameters in the scale of micron in elastic range were obtained. This investigation will be useful and helpful for the theoretical and numerical simulation of micro-structures and important for the design of the MEMS/NEMS.

Spider dragline silk exhibits a self-powered torsion actuation driven by humidity, potentially acting as a novel torsional actuator.

The plasticity of micron scale Cu and Au wires under cyclic torsion is investigated for the first time by using a torsion balance technique. In addition to a size effect, a distinct Bauschinger effect and an anomalous plastic recovery, wherein reverse plasticity even occurs upon unloading, are unambiguously revealed. The Bauschinger effect and plastic recovery have been observed in molecular dynamics and discrete dislocation dynamics simulations of ideal single-crystal wires; the results here are an excellent confirmation that these effects also occur in experiment in nonideal polycrystalline wires. A physical model consistent with the simulations is described in which the geometrically necessary dislocations induced by the nonuniform deformation in torsion play the key role in these anomalous plastic behaviors.