Thermal Actuation Based 3-DoF Non-Resonant Microgyroscope Using MetalMUMPs

Abstract

High force, large displacement and low voltage consumption are a primary concern for microgyroscopes. The chevron-shaped thermal actuators are unique in terms of high force generation combined with the large displacements at a low operating voltage in comparison with traditional electrostatic actuators. A Nickel based 3-DoF micromachined gyroscope comprising 2-DoF drive mode and 1-DoF sense mode oscillator utilizing the chevron-shaped thermal actuators is presented here. Analytical derivations and finite element simulations are carried out to predict the performance of the proposed device using the thermo-physical properties of electroplated nickel. The device sensitivity is improved by utilizing the dynamical amplification of the oscillation in 2-DoF drive mode using an active-passive mass configuration. A comprehensive theoretical description, dynamics and mechanical design considerations of the proposed gyroscopes model are discussed in detail. Parametric optimization of gyroscope, its prototype modeling and fabrication using MetalMUMPs has also been investigated. Dynamic transient simulation results predicted that the sense mass of the proposed device achieved a drive displacement of 4.1μm when a sinusoidal voltage of 0.5V is applied at 1.77 kHz exhibiting a mechanical sensitivity of 1.7μm /°/s in vacuum. The wide bandwidth frequency response of the 2-DoF drive mode oscillator consists of two resonant peaks and a flat region of 2.11 kHz between the peaks defining the operational frequency region. The sense mode resonant frequency can lie anywhere within this region and therefore the amplitude of the response is insensitive to structural parameter variations, enhancing device robustness against such variations. The proposed device has a size of 2.2 × 2.6 mm2, almost one third in comparison with existing M-DoF vibratory gyroscope with an estimated power consumption of 0.26 Watts. These predicted results illustrate that the chevron-shaped thermal actuator has a large voltage-stroke ratio shifting the paradigm in MEMS gyroscope design from the traditional interdigitated comb drive electrostatic actuator. These actuators have low damping compared to electrostatic comb drive actuators which may result in high quality factor microgyroscopes operating at atmospheric pressure.

Measurement of the properties of MetalMUMPS® thin films

“…MetalMUMPs® is the only commercial micro-machining process providing a thick structural metal film (a 20 J.lm nickel film plus a 0.5 J.lm top gold film) for constructing various MEMS devices [13]. Thus, the MetalMUMPs® process has been used for fabricating MEMS devices such as RF tuneable capacitors [14], RF inductors [15][16], RF switches [17], micro relays [18][19], a Cockcroft-Walton voltage multiplier [20], an electro-thermal actuator and thermal sensor [21 ], a 3-DOF gyroscope [22] and an electro-thermal actuated MEMS gripper [23].…”

Dynamics of a three-mass system with cubic nonlinearity and that of an equivalent electrical circuit

“…The vibration microgyroscope in [10] consists of three masses, two masses oscillate in the longitudinal direction, and the third one can also oscillate in the transverse direction, absorbing the vibrations of the active mass. This design, in combination with the proposed technological methods, improves the quality of the gyroscope.…”

Externally Induced Thermal Actuation of Polymer Nanocomposites

“…[28,29] In addition, heat could also directly induce expansion of the polymers because of the behavior of thermal expansion which is considered as one of the intrinsic material properties. [30,31] The way to apply thermal stimulation to polymer materials can be divided into external heating and internal heating. External heating provides direct heat to the sample by using heating elements around it, however, external-heating-induced thermal actuation may be restricted by non-uniform heating of the sample and the low rate of efficient heat transfer from the external heater to the sample surface, then into the inside of the sample.…”