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Micro Electro Mechanical Systems, 1989, Proceedings, An Investigation of Micro Structures, Sensors, Actuators, Machines and Robots. IEEE

Date 20-22 Feb. 1989

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Displaying Results 1 - 25 of 33
  • Proceedings: IEEE Micro Electro Mechanical Systems. An Investigation of Micro Structures, Sensors, Actuators, Machines and Robots (IEEE Cat. No.89THO249-3)

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    Freely Available from IEEE
  • Advances in processing techniques for silicon micromechanical devices with smooth surfaces

    Page(s): 71 - 75
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    The use of fine-grained polysilicon in the development of micromechanical devices (e.g. bearings, with smooth surfaces) is discussed. Fine-grained polysilicon can be produced with surface roughness near 8 Å r.m.s. (root mean square). The ability to anneal films of this type into tension eliminates size restrictions which are caused by compressive buckling. The use of these films in micromechanical devices has been restricted because hydrogen-fluoride-etched structures are covered by an etch residue which leads to contact welding. Contact between opposing surfaces is induced mainly by surface tension effects. This problem can be avoided by removing the deflection mechanism. Thus, freezing of a water-methanol rinse after sacrificial etching all but eliminates surface tension. Removal of the ice mixture via sublimation at 0.15 mbar occurs readily. Free-standing structures with smooth surfaces and small gaps are then passivated by silicon nitride deposition or other techniques View full abstract»

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  • A proposal for a superconducting actuator using Meissner effect

    Page(s): 107 - 112
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    A superconducting actuator with magnetic levitation using Meissner effect in μm order is proposed to remove the friction between moving elements and fixed elements in micromachines. The actuator, called Meissnac, is analyzed by the discrete surface current method. A driving method for the actuator is proposed. The driving force can be obtained by using the difference of the pitch of the stator and that of the slider, and the control of superconducting and normal states of superconductors. The control of the state can be achieved either by applying current over Jc to the superconductor or by heating it above Tc. Maximum values of the levitating force and the driving force are 1.7 and 0.26 (N/m2A2). The lateral movement in a particular direction of a slider is obtained by choosing appropriate superconductors and by transforming them into the normal state. A scale model is fabricated using a YBaCuO high-Tc superconductor. The levitating force and the driving force of a scale model are 84 and 31 (mgf) when the slider is composed of a permanent magnet View full abstract»

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  • Transduction mechanisms and their applications in micromechanical devices

    Page(s): 126 - 132
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    Transduction mechanisms and their applications in micromechanical actuators and resonating sensors are presented. They include piezoelectric, dielectric, electro-thermo-mechanic, opto-thermo-mechanic, and thermo-pneumatic mechanisms. Advantages and disadvantages with respect to technology and performance are discussed View full abstract»

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  • Electroquasistatic induction micromotors

    Page(s): 7 - 12
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    The steady-state operation of the electroquasistatic induction micromotor (IM) is investigated. A rotary pancake IM compatible with surface micromachining serves as an example. A model is developed to predict the electric potential, field, and free charge within the IM. The model also predicts the motive torque and transverse force of electric origin acting on its rotor. The torque is balanced against bushing friction and windage to determine rotor velocity; the bushing friction is modeled as a function of the transverse force acting on the rotor. The model is used to study IM performance and its dependence on IM dimensions and material properties. For example, IM performance is predicted to be a complex function of axial IM dimensions and a strong function of rotor conductivity. The study also reveals that IM performance can differ significantly from that of the variable-capacitance micromotor. For example, the dependence of motive torque and transverse force on velocity and the excitation and control requirements can all be significantly different View full abstract»

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  • IC-processed micro-motors: design, technology, and testing

    Page(s): 1 - 6
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    Micromotors having rotors with diameters between 60 and 120 μm have been fabricated and driven electrostatically to continuous rotation. These motors were built using processes derived from IC (integrated circuit) microcircuit fabrication techniques. Initial tests on the motors show that friction plays a dominant role in their dynamic behavior. Observed rotational speeds have thus far been limited to several hundred r.p.m., which is a small fraction of what would be achievable if only natural frequency were to limit the response. Experimental starting voltages are at least an order of magnitude larger than had been expected (60 V at minimum and above 100 V for some structures). Observations of asynchronous as well as synchronous rotation between the driving fields and the rotors can be explained in terms of the torque/rotor-angle characteristics for the motors View full abstract»

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  • Microstructures for fracture toughness characterization of brittle thin films

    Page(s): 40 - 41
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    A simple one-mask technique for characterizing fracture design parameters has been applied to tensile-stressed low-pressure chemical vapor deposited silicon nitride films. The design parameter obtained is the critical geometry parameter, which can be converted into fracture toughness by multiplying by the residual stress. Values of this parameter range from 14 to 290 μm1/2. Corresponding K I values are from 4.2 MPa-m1/2 to 87 MPa-m 1/2, assuming a residual stress of 300 MPa. Fabrication and test results are presented View full abstract»

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  • Design and fabrication of movable silicon plates suspended by flexible supports

    Page(s): 76 - 81
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    A process for fabricating silicon plates of varying thicknesses suspended by thin, flexible polyimide arms has been developed. The process uses bulk micromachining techniques and consists of four steps: a diaphragm etch from the back of the wafer; a trench etch from the front side (to define the plates); deposition and patterning of the plate support beams; and a self-aligned backside plasma etch to release the plates. The authors have used this process to fabricate square silicon plates two millimeters on a side and 7-10-μm-thick suspended by polyimide beams 500-μm long, 4-μm thick, and 100-200-μm wide. By evaporating aluminum on the topside of the plates, it was possible to deflect them electrostatically approximately 60 μm at 40 V applied voltage. These structures were designed for application as micromachined mirrors, although their sensitivity to motion and electrical and thermal isolation suggest other potential applications such as gas sensors, flow sensors, and accelerometers View full abstract»

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  • An operational harmonic electrostatic motor

    Page(s): 13 - 16
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    An operational harmonic electrostatic motor is described. A cylindrical rotor is placed inside a hollow cylindrical hole of slightly larger diameter. Electrodes on the circumference of the hole electrostatically attract the rotor and cause it to roll inside the stator. The harmonic motion of the rotor produces a gear reduction between the electrical drive frequency and the shaft rotation rate. This motor design has the advantage of increasing the torque of the motor. This motor has several other advantages. First, it uses the clamping force, normally larger than the tangential force used by most electrostatic motor designs, to generate the motion. Second, the sliding friction between the rotor and stator, a source of hindrance for most micro electrostatic motors, helps be keeping the rotor and stator from slipping. Third, this motor uses rolling surfaces that dissipate less energy in fiction than sliding surfaces View full abstract»

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  • Millimeter size joint actuator using shape memory alloy

    Page(s): 139 - 144
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    A millimeter-size actuator to drive a rotary joint for a small robot was designed and fabricated using shape memory alloy (SMA), which has the merits of large force/weight and extendability to micron size. The actuator is of the push-pull type, composed of two SMA sheets of 0.05 mm×0.5 mm×3 mm. The theoretical model of the dynamics of the SMA actuator was derived based on an experimental analysis of the dynamics of the larger SMA sheets. Using this model, the design method of the SMA actuator was established. Finally, the theoretical torque vs. angular displacement characteristic of a millimeter-size rotary joint driven by the above millimeter-size SMA actuator was obtained, which shows a maximum of 4 gf-mm View full abstract»

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  • Normally close microvalve and micropump fabricated on a silicon wafer

    Page(s): 29 - 34
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    A normally closed microvalve and micropump were fabricated on a silicon wafer by micromachining techniques. Normally closed microvalve has a silicon diaphragm and a small piezoelectric actuator to drive it. The controllable gas flow rate is from 0.1 ml/min to 85 ml/min at a gas pressure of 0.75 kgf/cm2. The micropump is a diaphragm-type pump which consists of two polysilicon one-way valves and a diaphragm driven by a small piezoelectric actuator. The maximum pumping flow rate and pressure are 20 μl/min and 780 mmH2O/cm2, respectively View full abstract»

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  • Selective chemical vapor deposition of tungsten for microdynamic structures

    Page(s): 82 - 87
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    A selective chemical vapor deposition (CVD) tungsten process is used to fabricate three-dimensional tungsten cantilever beams on a silicon substrate. Two beams form micromechanical tweezers that move in three dimensions by the application of potential differences between the beams, and between the beams and the silicon substrate. A high-deposition-rate selective tungsten CVD process is used to fabricate beams of greater than three microns thickness in patterned CVD SiO2 trenches ion-implanted with silicon. Tweezer 200-μm in length with a cross section of 2.7 μm×2.5 μm close with an applied voltage of less than 150 V. The magnitude of the deflection and the beam profile are compared to results obtained using simulations of the electric field and dynamic mechanical simulations of the tweezers View full abstract»

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  • OYSTER, a 3D structural simulator for microelectromechanical design

    Page(s): 88 - 93
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    OYSTER simulated the geometric effects of sequential IC (integrated circuit) process stages, including patterning of photoresists with planar masks, in order to produce three-dimensional polyhedral representations of all material structures in a design cell after each process stage. It has been developed for IC simulation but is applicable to microelectromechanical systems manufactured using similar processes. The polyhedral models may be used with various analytic procedures as sources of geometric data for finite-element calculations, or they may be subjected to interference calculations, or inspected to detect structural anomalies. As used in IC simulations, OYSTER provides the ability to introduce worst-case or stochastic manufacturing variations in mask alignment, etch depth, or deposition thickness. The author presents examples of variations in mask alignment and calculates resultant variations in center of gravity and moments of inertia for simple micromechanical objects View full abstract»

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  • A tele-microrobot for manipulation and dynamic mechanical testing of single living cells

    Page(s): 102 - 106
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    A high-performance parallel-drive microrobot has been developed for manipulation, surgery, and dynamic mechanical testing of single living muscle cells. The microrobot has two limbs which more in overlapping spherical workspaces of 1 mm diameter with minimum open-loop and closed-loop movements of 1 nm and 10 nm, respectively. Under nonlinear model-based control the limbs can move at up to 2 m/s relative to each other. Ferroelectric polymer microgrippers have been fabricated to facilitate cell manipulation. The microrobot has a three-dimensional laser vision system with a resolution of 50 to 100 nm. Volume images containing magnitude, phase, polarization, and spectral information can be acquired. The microrobot incorporates facilities to keep single living cells alive for long periods. A macro version of the microrobot has been built to allow force-reflecting teleoperation of the microrobot. The tele-microrobot system constitutes a mechanical microscope in which microscopic objects can be felt. The macro-interface also enables the operator to feel mechanical continuum models. A parallel computation and control computer has been designed to meet the substantial numerical requirements of the tele-microrobot system View full abstract»

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  • An electrostatic microactuator for electro-mechanical relay

    Page(s): 149 - 151
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    The author describes the design, the fabrication process, and the estimation of the characteristics of an electrostatic miniature relay. Its characteristics (contact force and response time) are estimated by the boundary-element method for the analysis of electrostatic fields. Problems regarding future development of the prototype and the future of microactuator technology and its applications are considered View full abstract»

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  • The world's largest one cubic inch robot

    Page(s): 98 - 101
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    The authors describe an exercise of building a complete robot system, aimed at being as small as possible, but using off-the-shelf components exclusively. The result is an autonomous one (almost) cubic inch robot which incorporates sensing. actuation, onboard computation, and onboard power supplies. Nicknamed Squirt this robot acts as a bug hiding in dark corners and venturing out in the direction of last-heard noises, only moving after the noises are long gone View full abstract»

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  • Miniature crystalline quartz electronical structure

    Page(s): 121 - 125
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    The photolithographic and chemical milling techniques used in fabricating a variety of three-dimensional monocrystalline quartz microstructures are presented. The piezoelectric effect, which is the electromechanical phenomenon utilized in the various applications of quartz technology, is described. Examples of quartz resonators used in sensing applications are presented. These miniature quartz sensors are incorporated into transducer systems which measure pressure, temperature, force, and acceleration. Some of the analytical tools used to design miniature quartz devices are outlined View full abstract»

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  • Sensor guided coronary deobstruction catheter

    Page(s): 42 - 43
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    Work in progress on the development of a nonsurgical deobstruction technique is described. The catheter in development is an advanced micromechanical device with an external diameter of 2 mm. The parts to be integrated in the catheter tip are: (1) an ultrasonic transducer for visualization of the internal diameter of the artery and tissue characterization; (2) an integrated ultrasonic transmitter-receiver for high signal quality; (3) a deobstruction unit using laser ablation or spark erosion; and (4) an optical position decoder View full abstract»

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  • Study on micro engines-miniaturizing Stirling engines for actuators and heatpumps

    Page(s): 145 - 148
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    The authors present micro-Stirling engines as a new potential field of micromachine study. The micro-Stirling engine is defined as a miniature Stirling engine, smaller than a few cubic centimeters. The purpose of this study is to establish the design concept and to realize a microactuator and a microheatpump. By applying dimensional analysis and computer simulation, the authors investigated how design parameters change when the engine size becomes smaller. A micro-Stirling engine of about 0.05 cm3 in a piston swept volume was realized. The output power is about 10 mW for 10 Hz vibration. Problems of miniaturizing the engines to the size of a few cubic millimeters are discussed View full abstract»

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  • The effects of post-process techniques and sacrificial layer materials on the formation of free standing polysilicon microstructures

    Page(s): 66 - 70
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    Through designed experimental analysis (ANOVA), the etchant concentration, percentage of overetch, and rinse agent used in the undercut process are shown to have significant effects on the size that polysilicon microstructures can be fabricated without collapse. This analysis is carried out for a variety of sacrificial layer materials, with results dependent on the material used. It is shown that these effects are so dramatic that the resulting strain level of the film may be difficult to determine without further analytical study. When microbridges, cantilevers, and proof rings are used to measure the local strain of thin films optically, it is shown that great care must be taken when interpreting the local strain and that further work is needed to develop procedures to eliminate this problem and formulate a theoretical explanation for the physical forces behind the results observed View full abstract»

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  • Micro actuators for aligning optical fibers

    Page(s): 35 - 39
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    Two microactuators to align fiber optics are described. One, an actuator using a thin strand of shape memory alloy, is used to align an input fiber with one of two output fibers. This component is useful for switching fiber-optic signals. The second is an electrostatic actuator capable of switching optical fibers and making fine adjustments to correct for misalignments. Single-point diamond machining (and associated molding technology) has been shown to be a viable alternative to etching Vee grooves in silicon for holding and aligning fibers View full abstract»

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  • Applications of silicon microactuators based on bimorph structures

    Page(s): 116 - 120
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    Microactuators for electromechanical signal conversion are described. Basic elements of the transducer are a bimorph structure and an integrated heat source. Due to the differences of the coefficients of thermal expansion, a temperature-controlled deformation of the the bimorph structure occurs. Bulk and surface micromachining techniques can be used to achieve an object displacement perpendicular to or within the substrate plane. The main advantages of this class of actuators are simple fabrication processes and operation at standard IC (integrated circuit) voltage levels, allowing further system integration. The conversion characteristics are described, and the application of these transducers for microvalves, optical components, manipulators, and motors is discussed View full abstract»

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  • Residual strain effects on large aspect ratio micro-diaphragms [capacitance transducer]

    Page(s): 133 - 138
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    The authors describe techniques that result in low-strain materials and that reduce the effects of residual strain in microdiaphragms, which are used in capacitive-readout sensors. Square polysilicon grilles and perforated diaphragms made from both single and double polysilicon layers and from single-crystal silicon, with aspect ratios (side/thickness) of up to 1000 and very low compressive strain (about 6×10-5), have been fabricated. Strain reduction is achieved by combining thermal annealing with one of two mechanical design techniques. The first technique makes use of a series of cantilever beams to support the diaphragms. In a second procedure, corrugated surfaces, in thinned membranes of single-crystal silicon are formed. The corrugations result from the use of boron doping and anisotropic silicon etching. In both of these techniques to produce low-strain diaphragms, an etched cavity is purposely formed in the substrate crystal below them. Only one-sided processing of wafers is used, thus aiding reproducibility and providing ease of compatibility with a metal-oxide-semiconductor process. A fast etching sacrificial-support layer (phosphorus-doped chemical-vapor-deposited oxide) is used View full abstract»

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  • Fluid flow in micron and submicron size channels

    Page(s): 25 - 28
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    Experiments on flow in micron- and submicron-size channels were conducted. The long-term objectives of the study were to investigate: (1) the length scales at which continuum assumptions break down; (2) whether the Navier-Stokes (N-S) equations adequately model the fluid flow in these very small scales or whether should they be modified and, if so, how; (3) whether phenomena which typically are ignored at large scales become important at small scales; and (4) whether transition to turbulence is affected by the small size of the channels. The test structure consisted of a single channel etched in silicon using planar photolithographic micromachining techniques. Tentative results are reported. It is observed that, in channels with relatively large cross-sections, the fluid roughly behaves in accordance with predictions based on the N-S equations. In smaller-size channels there are large deviations between experimental observations and N-S predictions View full abstract»

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  • Tuning forks in silicon

    Page(s): 94 - 95
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    The authors describe microfabricated tuning forks in silicon, which are excited electrodynamically. The pressure dependence of the resonance frequency and the Q-factor was measured by an interferometer over a range of pressure 1 μbar to 2 bar. It is shown that micromachined structures in silicon have Q-factors which are comparable to those of similar quartz structures View full abstract»

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