Previous works on suspended carbon nanotube and nanowire resonators assume a priori that they oscillate in a single plane. We explore the nonlinear dynamics of such resonators and demonstrate that they can suddenly transition from a planar motion to a whirling, "jump rope" like motion. We identify nondimensional gate voltage, resonator geometry, quality factor, and flexural and axial elastic stiffnesses for which such motions can arise. The deliberate use of nonlinear and nonplanar motions opens up a variety of new modalities for this class of nanoelectromechanical systems that are not accessible in the linear operating regime.

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A finite element model has been developed to investigate the engagement of rough, grooved, paper-based permeable wet clutches. The finite element (Galerkin) approach was used to discretize the modified Reynolds and force balance equations, and the solution domain geometry was described using an isoparametric formulation. Surface roughness effects were modeled via the Patir and Cheng (1978) average flow model, while asperity load sharing was calculated using the Greenwood and Williamson (1966) approach. The finite element model developed, was used to investigate the effects of applied load, friction material permeability, and groove size on the engagement characteristics of wet clutches (i.e., torque, pressure, engagement time, and film thickness). The results indicate that the applied load, friction material permeability, and groove width significantly influence the engagement characteristics. Higher facing pressures increase peak torque and decrease engagement time. Higher permeability of the friction material significantly decreases engagement time but dramatically increases peak torque. Wider grooves decrease the peak torque and increase the engagement time. Groove depth does not significantly affect engagement characteristics for this model.