Localized Mechanical Actuation using pn Junctions

Abstract

We are reporting on the fabrication and characterization of microscale electromechanical actuators driven by the internal forces induced within the depletion region of a typical pn junction. Depletion region actuators operate based on the modulation of the interactions of the internal electric field and the net space charge within the depletion region of a pn junction by an external potential. In terms of performance, depletion region actuators fall between electrostatic actuators, where a physical gap separates the charges on two electrodes, and piezoelectric actuators, where the separation between the charges is on the order of lattice constants of the material. An analytic model of depletion region actuator response to an applied potential is developed and verified experimentally. The prototype micro-mechanical device utilized the local stresses produced by the depletion region actuators to generate mechanical vibrations at frequencies far below the resonance frequencies of the structure. A laser Doppler vibrometer was used to measure and compare the displacements and vibration patterns caused by the depletion region and electrostatic actuators. Utilizing depletion region actuators neither requires etching of narrow gaps, which is technically challenging nor is there a need for introducing piezoelectric materials into the fabrication process flow. The simple operating principle and the possibility of exploiting the technique for various optimized linear or nonlinear actuation at small scales provide opportunities for precise electro-mechanical transduction for micro- and nano-mechanical devices. These actuators are therefore suited for the co-fabrication of micro- and nano-mechanical systems and microelectronic circuits. Additionally, the produced strains depend only on the depletion region specifications and the excitation voltage and do not scale with device dimensions. As such, depletion region actuators can be candidates for efficient nanoscale electromechanical actuation.

Localized Photoactuation of Polymer Pens for Nanolithography

“…Substantial progress has been made on the deformation of the macroscopic material/system under external stimuli. Nevertheless, local actuation with high spatiotemporal precision, resolution, and selectivity remains one of the exciting challenges in nanotechnology owing to the wealth of fundamental questions and ample potential applications in programmable materials, micro/nano robotics, haptic rendering, and precision medicine, [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ] towards which efforts are needed in both material science and device engineering. It is essential to comprehend the microscopic condition of the functional components in the composites, including the microarchitecture, interface chemistry, and assembly/embedding strategy.…”