Dielectric elastomer generators (DEGs) can convert mechanical energy into electricity based on variable capacitance. DEGs can potentially harvest energy from renewable energy source such as wind and ocean waves due to their light weight, low cost, and high energy density. To scale up the energy output, multiple single-layer generator units are stacked to form a multilayer DEG. The fabrication of DEGs with reliable multilayer structure having high deformability and long-term stability remains a critical challenge. We report a scalable multilayering technique to produce robust DEG stacks with circular diaphragm configuration. A 4-layer stacked VHB films showed a threefold voltage gain during constant charge operation and an estimated energy density of 100 J/kg. Furthermore, by introducing a dielectric elastomer binder between the VHB films, we demonstrate strong interlayer adhesion in the stacked DEGs, enabling long-term operation stability. As a result, a 4-layer circular diaphragm DEG survived more than 100,000 cycles of mechanical deformation between 0 and 100% area strain. Carbon nanotube (CNT) coating was used as the compliant electrode. Its resistance remains almost constant after 4000 cycles of conditioning.
I describe the electrically-driven rotation of 2.4-micron-radius, optically levitated dielectric microspheres. Electric fields are used to apply torques to a microsphere's permanent electric dipole moment, while angular displacement is measured by detecting the change in polarization state of light transmitted through the microsphere. This technique enables greater control than previously achieved with purely optical means. We measure the spin-down of a microsphere released from a rotating electric field, the harmonic motion of the dipole relative to the instantaneous direction of the field, and the phase lag between the driving electric field and the dipole moment of the MS due to drag from residual gas. We also observe the gyroscopic precession of the MS when the axis of rotation of the driving field and the angular momentum of the microsphere are orthogonal. These observations are in quantitative agreement with the equation of motion.
Optical traps for dielectric particles have become an exceptional tool in testing optomechanics as well as fundamental physics. We report on our use of optical trapping in a program searching for non-Newtonian gravity, as well as recent tests that demonstrate control of the rotational degrees of freedom of optically trapped particles via electrostatic interactions with the dipole moments of test particles. The technique levitates individual micrometer-sized dielectric spheres and measures their three-dimensional position by optical heterodyne detection, making use of a single laser for both trapping and imaging. The two radial degrees of freedom are measured by interfering light transmitted through the microsphere with a reference wavefront, while the axial degree of freedom is measured from the phase of the light reflected from the surface of the microsphere. This method pairs the simplicity and accessibility of single-beam optical traps to a measurement of displacement that is intrinsically calibrated by the wavelength of the trapping light and has exceptional immunity to stray light. A theoretical shot noise limit of 1.3e-13 m/rt{Hz} for the radial degrees of freedom, and 3.0e-15 m/rt{Hz} for the axial degree of freedom can be obtained in the system described. The measured acceleration noise in the radial direction is 7.5e-5 (m/s^2)/rt{Hz}.
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