A versatile MEMS bimorph actuator with large vertical displacement and high resolution: Design and fabrication process

Abstract: Micropositioning systems are widely used in many applications, for example, optical industry, medical devices, and micro-assembly applications. Commonly, MEMS-based micropositioning systems use conventional fabrication techniques such as lithography, etching, and thin-film processes. However, a typical microfabrication process by using the masking and etching operations is limited to fabricate a 3-dimensional complex device. This research presents a novel design of a 3D micropositioning system with electrostatic comb drives with a converting mechanism. The device can convert the in-plane motion to the out-of-plane displacement. The proposed model is possible by using FEMTOPRINT®, machine which combines material modification by femtosecond laser-beam and chemical wet etching. The results from the simulation shown that the 3Dcomplex micropositioning system can achieve a wide range of workspace up to 1$,212.79 \mu \mathrm{m}^{2}$. In X-axis and Z-axis, it can translate up to a maximum displacement of $33.34 \mu \mathrm{m}$ and $75.14 \mu \mathrm{m}$ respectively, while the footprint of the device is $1.65 \times 1.10$ mm2. This device can be a new prototype of MEMS based-micropositioning system named “glassy MEMS” that is suitable for a 3D-complex mechanism and can be used in many applications.

Abstract: Electro-thermal (E-T) actuators have been developed to complement the capabilities of electrostatic actuators. The thermal actuators presented here can be arrayed to generate high forces. Equally significant is that the single actuators and arrays of actuators operate at voltages and currents that are directly compatible with standard microelectronics. This paper demonstrates how combinations of two or more electro-thermal actuators can be applied to a variety of basic building-block micromechanical devices: array of ten lateral actuators; array of ten vertical actuators; vertically actuated two-axis tilting mirror; corner-cube retroreflector actuated by lateral array; grippers over the die edge with flip-over wiring; rotary stepper motor; flip-up optical grating on rotary stepper motor; linear stepper motor; and a linear stepper motor for assembly of hinged structures.

Abstract: The authors present a model of the electromechanical performance of bimetallic cantilever microactuators by deriving the relationship between the tip deflection and change in temperature using a simple analytical approach. The model is verified by comparison with finite element analysis and published experimental data. The maximum tip force generated by a bimetallic cantilever beam is calculated by finding the reaction force needed at the tip to prevent cantilever beam deflection.

Abstract: This paper presents a novel approach for constructing a tunable dielectric resonator bandpass filter by using the microelectromechanical system (MEMS) technology. The tunability is achieved by unique MEMS tuning elements to perturb the electrical and magnetic fields surrounding the dielectric resonators. The use of such elements as a tuning mechanism results in a wide tuning range at a relatively low tuning voltage and fast tuning speed. A three-pole tunable dielectric resonator bandpass filter is designed, fabricated, and tested. The experimental filter has a center frequency of 15.6 GHz, a 1% relative bandwidth, and an unloaded Q of 1300. A tuning range of 400 MHz is obtained by using MEMS tuning elements with 2 mmtimes2 mm tuning disks. The measured results demonstrate the feasibility of the proposed concept

Abstract: A novel silicon on insulator (SOI) MEMS process has been designed and developed to realize a two axes thermally actuated single crystal silicon micromirror device, which consists of a mirror plate, four flexural springs and four thermal actuators The mirror plate has the same thickness as a SOI device layer ie 4 µm The SOI layer is selectively thinned down to 2 µm for fabricating flexural springs and thermal actuators The thinning of the SOI layer is essential to lower (control) the flexural rigidity of the springs and the actuators and thus to achieve a higher tilt angle at low thermal power The developed single wafer process is based on dry reactive ion etching CMOS compatible chemistries The minimum chip size design of 1 mm × 1 mm has a 400 µm diameter mirror plate Other chip designs include the mirror diameters in the range from 200 to 500 µm This paper also presents a study on the mirror plate curvature, thermal actuation mechanism and the experimental results The measured maximum angular deflection achieved was 17° at an operating applied voltage of less than 2 V, and the radius of curvature of the mirror plate was in the range from 20 to 50 mm The micromirror was developed for a miniature catheter optical probe for optical coherence tomography in vivo imaging A low cross-sectional size of the probe and higher resolution are essential for investigating inaccessible pathologies in vivo This required a compact micromirror chip and yet sufficiently large mirror plate (typically ~500 µm or more), this trade-off was the key motivation for the research presented in this paper

Abstract: This paper presents the design and testing results of an electrothermally driven MEMS (microelectromechanical systems) actuator. Different from conventional uni-directional U-beam thermal actuators, this in-plane bi-directional electrothermal (IBET) actuator is capable of producing displacements in two directions as a single device. It is important to note that merely coupling two conventional uni-directional U-beam electrothermal actuators is insufficient to achieve bi-directional motion, as the resistance from the oppositely configured actuator severely limits net motion and leads to poor performance. An optimized IBET design was obtained through numerical simulation using finite element modeling. The devices were fabricated using the standard polyMUMPs surface micromachining process. Experimental results demonstrate that the IBET microactuators have a displacement range of 12 µm (6 µm in either direction).