An electrostatic lower stator axial-gap polysilicon wobble motor.II. Fabrication and performance

For pt. I see ibid., vol. 7, no. 1, p. 79-86 (1998). This paper presents the fabrication and first performance characteristics of electrostatically driven axial-gap polysilicon wobble motors. The fabrication is based on a four mask process using polysilicon surface-micromachining techniques. Three twelve-stator-pole wobble motor designs have been realized with rotor radii of 50 and 100 μm. Motors have been operated successfully at driving voltages as low as 6 V at speeds up to 150 rpm. The motor performance is characterized by gear ratio measurements and measuring starting and stopping voltages. Motor lifetimes of several million wobble cycles, comparable to operating times of several hours, have been obtained     

Micro liquid rotor operated by surface-acoustic-wave

A micro liquid rotor operated by surface acoustic waves (SAWs) was proposed and fabricated. The liquid rotor has two interdigital transducers (IDTs) that generate SAWs, in order to increase efficiency of rotating the liquid. The IDTs were fabricated by patterning Al/Cr on a LiNbO₃ substrate. Moreover, the liquid rotor has a cylindrical liquid pool of 4 mm diameter and 200 μm depth. A sidewall of the liquid pool was made of epoxy-based negative photoresist on the substrate. As characteristics of the liquid rotor, we investigated relationships between electric power applied to the IDTs and angular velocity of the liquid or its temperature. Through experimentation, it was shown that the angular velocity and the temperature increase with increasing the electric power. When the fabricated liquid rotor was applied electric power of 2 W, the liquid of 5 μL rotated at 330 rad/s (3,100 rpm) and its temperature reached 65°C.     

Average power control and positioning of polysilicon thermal actuators

This paper reports on characterizing and modeling the behavior of micromachined polysilicon thermal actuators when driven by DC or pulsed drive signals. Thermal actuators can be controlled and positioned using a pulsed input with a period much less than the thermal time constant of the device as demonstrated by data collected in air and vacuum. Both pulse width and pulse amplitude modulation were successfully employed to position lateral actuators, lateral actuator arrays, and piston micro-mirrors. A SPICE model for polysilicon thermal actuators was developed using relationships between resistance, deflection, and average power. This model incorporates the polysilicon thermal actuator's electrical load, transient response, and deflection characteristics necessary for predicting actuator performance and developing microsystems. The SPICE model exhibits very close agreement with the measured performance of the polysilicon thermal actuators.     

An electrostatic lower stator axial-gap polysilicon wobble motor.I. Design and modeling

This paper presents design issues and a theoretical model of electrostatically driven axial-gap polysilicon wobble motors. The motor design benefits from large axial rotor-to-stator overlap and large gear ratios, and motor designs with rotor radii of 50 and 100 μm are capable of generating torques in the nanoNewtonmeter range at high electrostatic fields. Because of the large gear ratio, smaller angular steps and lower rotational speed are obtained, compared to radial-gap motor designs. Aspects like gear ratio, torque generation, excitation schemes and torque coverage, normal forces, friction, rotor kinetics, and dynamical behavior are addressed. The motor design is compliant to the integration of gear linkages with respect to mechanical power transmission     

An electro-thermally driven microactuator with two dimensional motion

 In previous literatures, most of the microactuators were designed to deflect in one dimension only. Here, an electro-thermally driven microactuator with out-of-plane and in-plane two dimensional motion is designed, fabricated and tested. This microactuator comprised of a series of bimorph beams, a moving plate, a lateral driven unit, and contact pads. The out-of-plane motion is produced due to the bimorph effect and residual stress between the layers of Au and polysilicon when they are heated. The in-plane motion is obtained by heating the lateral driven unit which consists of two adjacent beams with different cross sections but the same length, then the asymmetrical thermal expansions in two adjacent beams lead to lateral deflection. The microactuator proposed here is fabricated by surface micromaching technique. A two-step releasing method is used here to free the microactuator successfully. The testing results show that the lateral driven unit can produce 10 μm lateral displacements at input voltages of 5 V, and bimorph structures at the same voltage can produce about 12 μm downward displacement. It is also found that this two dimensional motion can be controlled almost independently. Received: 21 May 2001/Accepted: 30 July 2001     

Studies on a micro turbine device with both journal- and thrust-air bearings

This paper presents design, fabrication, analysis and test of a silicon-based micro turbine device that is driven by compressed air. To improve the motion stability at high rotational speed, the turbine device employs an enhanced micro air bearing system that includes both journal air bearing and thrust air bearings. The double-sides dynamic thrust air bearings are designed to support the rotor from both its top and bottom sides. The top thrust air bearing employs pump-in spiral groove configuration, and the bottom bearing uses pump-out spiral groove configuration. The dynamic journal air bearing is formed by a plain circular trench with a short journal length (L) and a narrow radial clearance (C). The critical aspect ratio (L/C) over 20:1 is realized through an optimized fabrication process. The micro turbine device has been fabricated, integrated and tested. During the test, the turbine device demonstrated stable operations at a rotational speed of 14,700 rpm.     

A simple fabrication process for polysilicon side-drive micromotors

A simple fabrication process for rapid prototyping of side-drive polysilicon micromotors has been developed. This process uses three low-pressure chemical vapor depositions and three photolithography steps, and it enables fabrication of new micromotors and flange bearing designs. An important feature of this process is that the rotor, stator, and rotor/stator gap pattern definition is the first photolithography step and is performed over a flat surface. As a result, excellent linewidth resolution is possible for defining the rotor/stator gaps. Conventional wobble and salient-pole micromotors fabricated with this process have been operated for months after release, For wobble micromotors with 3-μm-thick rotor/stator polysilicon films, minimum operating voltages have been 25 V across 1.5-μm rotor/stator gaps; maximum operating speeds have been 1000 rpm. limited by the power supply. Corresponding salient-pole micromotors have had minimum operating voltages of 50 V; their maximum operating speeds have been near 5000 rpm     

High aspect-ratio combined poly and single-crystal silicon (HARPSS)MEMS technology

This paper presents a single-wafer high aspect-ratio micromachining technology capable of simultaneously producing tens to hundreds of micrometers thick electrically isolated poly and single-crystal silicon microstructures. High aspect-ratio polysilicon structures are created by refilling hundreds of micrometers deep trenches with polysilicon deposited over a sacrificial oxide layer. Thick single-crystal silicon structures are released from the substrate through the front side of the wafer by means of a combined directional and isotropic silicon dry etch and are protected on the sides by refilled trenches. This process is capable of producing electrically isolated polysilicon and silicon electrodes as tall as the main body structure with various size capacitive air gaps ranging from submicrometer to tens of micrometers. Using bent-beam strain sensors, residual stress in 80-μm-thick 4-μm-wide trench-refilled vertical polysilicon beams fabricated in this technology has been measured to be virtually zero. 300-μm-long 80-μm-thick polysilicon clamped-clamped beam micromechanical resonators have shown quality factors as high as 85 000 in vacuum. The all-silicon feature of this technology improves long-term stability and temperature sensitivity, while fabrication of large-area vertical pickoff electrodes with submicrometer gap spacing will increase the sensitivity of micro-electromechanical devices by orders of magnitude     

Controlled stepwise motion in polysilicon microstructures

This paper presents a polysilicon slider and a rotor capable of stepwise motion. These devices were fabricated on a silicon wafer with surface micromachine technology. The proportional relation between the velocity of motion and the frequency of the applied pulse was experimentally confirmed. The peak value of the applied pulse determines the step length. The step values observed were in the range of 10-30 nm for a bushing height of 1.0 μm and of 40-80 nm for a bushing height of 2.0 μm depending on the peak voltage of the applied pulse     

Modeling of angular-rate bandwidth for a vibrating microgyroscope

A new analysis on the angular-rate bandwidth characteristics of a vibrating microgyroscope is proposed. Employing a dynamic model for a vibrating microgyroscope, the frequency response of the vibrating microgyroscope is analyzed with respect to an input angular rate. A microgyroscope, in which an inertial mass vibrates on a substrate plane, is designed and fabricated by surface micromachining technology using polysilicon structures on an insulation layer. The fabricated microgyroscope was operated in a vacuum environment of 100 mtorr, and showed the sensitivity of 5 mV s/° with the noise level of 1 mV. Bandwidth characteristics of the microgyroscpes were also investigated by comparison with the simulation on the bandwidth model, and the validity of the proposed dynamic model was evaluated.     

Robot Leg Motion in a Planarized-SOI, Two-Layer Poly-Si Process

With the ultimate goal of creating autonomous microrobots, we developed a five-mask process that combines two polysilicon structural layers with 50-$mu m$-thick SOI structures and a backside substrate etch. The polysilicon layers provide three-dimensional (3-D) hinged structures, high compliance structures, and electrical wiring. The SOI structural layer yields much stronger structures and large-force actuators. This process was developed as a part of a three-chip solution for a solar-powered 10-mg silicon robot. Here, we describe the fabrication of this planarized-SOI, two-layer poly-Si process (henceforth called the SOI/poly process), basic modules in the design of robot legs in this process, and lastly, the results of fabricated robot legs. In designing the leg structures, we developed guidelines and test structures to provide a better understanding of the robot leg performance. These guidelines include understanding the relationship between the lateral etch depth to the actuator spacing and performing static friction tests of polysilicon flaps to more accurately model the frictional forces of the linkages. Last, we report on the performance of the robot legs and inchworm motors. On an 8 mm$times$3 mm robot, we have demonstrated a 1 degree-of-freedom (DOF) robot leg, 1 mm in length, which demonstrates up to 60$mu N$of vertical leg force with an angular deflection of almost 30$^circ$. A two-DOF robot leg, also 1 mm in length, operated with at least 90$^circ$of angular deflection, and each inchworm motor demonstrated a shuttle displacement of 400$mu m$with speeds up to 6.8 mm/s. In addition to robot legs, a bidirectional inchworm motor that produces equivalent forces in both directions was also fabricated in this SOI/poly process. This motor uses an additional set of gap-closing-actuator (GCA) arrays to prebias the drive frame.hfill hbox[1305]     

Integrated polysilicon and DRIE bulk silicon micromachining for anelectrostatic torsional actuator

This paper presents a fabrication process that integrates polysilicon surface micromachining and deep reactive ion etching (DRIE) bulk silicon micromachining. The process takes advantage of the design flexibility of polysilicon surface micromachining and the deep silicon structures possible with DRIE. As a demonstration, a torsional actuator driven by a combdrive moving in the out-of-plane direction, consisting of polysilicon fingers and bulk silicon fingers, has been fabricated. The integrated process allows the combdrive to be integrated with any structure made by polysilicon surface micromachining     

High-Q single crystal silicon HARPSS capacitive beam resonators with self-aligned sub-100-nm transduction gaps

This paper reports on the fabrication and characterization of high-quality factor (Q) single crystal silicon (SCS) in-plane capacitive beam resonators with sub-100 nm to submicron transduction gaps using the HARPSS process. The resonating element is made of single crystal silicon while the drive and sense electrodes are made of trench-refilled polysilicon, yielding an all-silicon capacitive microresonator. The fabricated SCS resonators are 20-40 /spl mu/m thick and have self-aligned capacitive gaps. Vertical gaps as small as 80 nm in between 20 /spl mu/m thick silicon structures have been demonstrated in this work. A large number of clamped-free and clamped-clamped beam resonators were fabricated. Quality factors as high as 177000 for a 19 kHz clamped-free beam and 74000 for an 80 kHz clamped-clamped beam were measured under 1 mtorr vacuum. Clamped-clamped beam resonators were operated at their higher resonance modes (up to the fifth mode); a resonance frequency of 12 MHz was observed for the fifth mode of a clamped-clamped beam with the fundamental mode frequency of 0.91 MHz. Electrostatic tuning characteristics of the resonators have been measured and compared to the theoretical values. The measured Q values of the clamped-clamped beam resonators are within 20% of the fundamental thermoelastic damping limits (Q/sub TED/) obtained from finite element analysis.     

SB70变频器、自整角机与角位移变送器在矿用提升机上的应用

本文介绍了传统的绕线式电动机转子串电阻调速方式提升机。结合该矿井提升机的实际条件,采用变频器、自整角机和角位变送器,对其进行改造以实现变频无级调速。在改造时保留原来的工频系统作为备用,并保持原有的操作装置和操作习惯。     

Compact and power‐saving polysilicon data driver with common‐decoder DA converter (CD‐DAC)

Abstract— A common‐decoder architecture for a data‐driver circuit fabricated by using a polysilicon process has been developed. The architecture achieves a compact circuit and low‐power consumption. In application to an integrated polysilicon data driver for small‐sized displays, this architecture reduces the area of the data driver by removing the vertical bus lines that occupy a large area. It also suppresses the power consumption of the data bus by reducing the number of driven lines in the data bus during word‐to‐word transitions from six to two. By using a conventional 4‐μm design rule, we fabricated an active‐matrix OLED (AMOLED) panel with an integrated six‐bit data‐driver circuit with 384 outputs. The driver circuit had a height of 2.6 mm and a pitch between output lines of 84 μm. The maximum power consumption of the driver was only 5 mW, i.e., 3.8 mW for logic‐data transfer and 1.2 mW for reference‐voltage source. Furthermore, we also fabricated an active‐matrix LCD (AMLCD) panel including driver circuits of the same type as the integrated elements. Six‐bit full‐color images were successfully displayed on both panels.     

Two-Axis Microstage System

We report on the design, fabrication, and testing of a two-axis stage that was used to move a cantilever arm. We utilized Sandia National Laboratories' MEMS foundry process that incorporates five levels of polysilicon and four sacrificial layers of silicon dioxide. The $X$– $Y$ stage was actuated with the full 110 $muhbox{m}$ of travel in both dimensions. To demonstrate the travel of the stage, a cantilevered arm was attached to the stage and extended off the edge of the chip. Rotational motion from torsional ratcheting actuators is converted to linear motion through an intricate mechanical system. The rotational engines drive two independent spiral cams that provide the linkage system with the angular to linear translation needed to move the stage arms. A pin and the slotted $X$ –$Y$ stage arms allow motion in both the $X$ - and $Y$ -directions. This initial device has been successfully operated and demonstrates a useful design for producing 2-D motion using a MEMS. The unidirectional rotational drives used in these experiments did not allow the retraction of the stage, but there appears to be a clear path to back-and-forth motion using bidirectional rotational drives or linear actuators.$hfill$ [2007-0273]      

Magnetic microactuation of polysilicon flexure structures

A microactuator technology that combines magnetic thin films with polysilicon flexural structures is described. Devices are constructed in a batch-fabrication process that combines electroplating with conventional lithography, materials, and equipment. A microactuator consisting of a 400×(47-40)×7 μm³ rectangular plate of NiFe attached to a 400×(0.9-1.4)×2.25 μm³ polysilicon cantilever beam has been displaced over 1.2 mm, rotated over 180°, and actuated with over 0.185 nNm of torque. The microactuator is capable of motion both in and out of the wafer plane and has been operated in a conductive fluid environment. Theoretical expressions for the displacement and torque are developed and compared to experimental results     

A Two Degree of Freedom Gripper Actuated by SMA with Flexure Hinges

A gripper prototype was designed and built. It is made by a rigid structure articulated by compliant hinges. Its kinematics consists of both parallel and angular finger motion. The movements were designed to be independent from each other and auto‐adaptive as well. The motions were driven by Ni‐Ti shape memory alloy (SMA) wires. The recovery position is achieved by the elastic force exerted by the flexure hinges in the case of parallel motion and by an axial spring in the case of angular motion. Both the actuators and the hinges were experimentally characterized by suitable test rigs. The gripper prototype was tested and it showed to be able to reach the design performances. © 2003 Wiley Periodicals, Inc.     

A resonant, dielectric micro-motor driven by low ac-voltages (<6V)

 An asynchronous, dielectric micro-motor consisting of an Al-SiO₂ rotor of 50 to 200 μm diameter was driven with 4 or 8 circularly arranged electrodes in water. The motor elements were fabricated by micromachining. Each electrode was designed to be an oscillatory circuit with a sharp resonance frequency in the upper kHz-range. The resonances at all electrode tips increase the voltage in the stator-rotor gap by a factor of up to 15. As a result, the dielectric rotor operates in a sharp frequency window at 5 V_pp excitation as if driven with more than 75 V_pp. With square wave pulses, the higher order Fourier-components induce several changes in rotor spin direction within two frequency decades. The micro-motor has been driven for hours without noticeable wear. It developed high starting torques and was useful for circular water pumping. The system has the advantage of very sensitive frequency dependence and the low drive voltages (below 10 V) can be produced by most electronic circuits. Received: 2 December 1996/Accepted: 15 January 1997     

A simple approach to characterizing the driving force of polysilicon laterally driven thermal microactuators

Based on the elastic analysis of structures, a simple approach to calculating the driving force for polysilicon laterally driven thermal microactuators is presented by using their deflection. The driving force obtained through the deflection is compared with available results measured by force testers fabricated on the same substrate as the microactuators. Reasonable agreement has been achieved. The approach allows one to predict the driving force for the microactuators as their deflection is designed.