Quality factor (Q) is an important property of micro- and nano-electromechanical (MEM/NEM) resonators that underlie timing references, frequency sources, atomic force microscopes, gyroscopes, and mass sensors. Various methods have been utilized to tune the effective quality factor of MEM/NEM resonators, including external proportional feedback control, optical pumping, mechanical pumping, thermal-piezoresistive pumping, and parametric pumping. This work reviews these mechanisms and compares the effective Q tuning using a position-proportional and a velocity-proportional force expression. We further clarify the relationship between the mechanical Q, the effective Q, and the thermomechanical noise of a resonator. We finally show that parametric pumping and thermal-piezoresistive pumping enhance the effective Q of a micromechanical resonator by experimentally studying the thermomechanical noise spectrum of a device subjected to both techniques.

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A bristle-bot or vibrobot is a multi-legged robot made of bristles and an oscillating actuator that generates vibrations. This work presents the first demonstration of a microbristle-bot, with 3D-printed legs, fabricated by two-photon polymerization (TPP) lithography. The presented miniaturized bristle-bot has a weight of only 5 mg, in the size of 2 mm × 1.87 mm × 0.8 mm, and can achieve a speed up to 4 times the body length per second. A base structure with six legs is fabricated by TPP direct laser writing in a single fabrication step, allowing for rapid prototyping of various leg designs. The base is attached to a 0.3 mm thick lead zirconate titanite (PZT) actuator block. The vibrational energy is provided by an external piezoelectric shaker in this work, which mimics the ocillatory behavior of the on-board PZT block. This work demonstrates the locomotion of micro-bristle-bots with various leg designs that utilizes the resonant bending mode shape at small excitation voltages applied to the external piezoelectric shaker. The presented micro-bristle-bots show a resonant frequency around 6.3 kHz, which can be tailored based on their geometry. This feature allows for addressing individual micro-bristle-bots with various geometries based on their unique resonance frequency.

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