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  Self-stabilizing, floating microelectromechanical deviceUSPTO Application #: 20080100175Title: Self-stabilizing, floating microelectromechanical device Abstract: The present invention relates to MicroElectroMechanical Systems (MEMS), devices and applications thereof in which a proof mass is caused to levitate by electrostatic repulsion. Configurations of electrodes are described that result in self-stabilized floating of the proof mass. The electrical properties of the electrodes causing floating, such as currents and/or voltages, typically change in response to environmental perturbations affecting the proof mass. Measuring such currents and/or voltages allow immediate and accurate measurements to be performed related to those perturbations affecting the location and/or the orientation of the proof mass. Additional sensing electrodes can be included to further enhance sensing capabilities. Drive electrodes can also be included that allow forces to be applied to the charged proof mass resulting in a floating, electrically controllable MEMS device. Several applications are described including accelerometers, inertial sensors, resonators and filters for communication devices, gyros, one and two axis mirrors and scanners, among other devices. Several fabrication methods are also described. (end of abstract) Agent: Michaelson & Associates - Red Bank, NJ, US Inventor: Jason Vaughn Clark USPTO Applicaton #: 20080100175 - Class: 310309 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20080100175. Brief Patent Description - Full Patent Description - Patent Application Claims
CLAIM TO PRIORITY [0001]This application is a divisional of, and claims the benefit of, our co-pending United States application entitled "Self-Stabilizing, Floating Microelectromechanical Device" filed Apr. 30, 2004 and assigned Ser. No. 10/836,562, the entire contents of which, including all attachments thereto, are hereby incorporated herein by reference for all purposes. BACKGROUND OF THE INVENTION [0002]1. Field of Invention [0003]This invention relates generally to the field of microelectromechanical (MEMS) devices and, in particular, to floating MEMS devices in which a proof mass is electrostatically levitated. [0004]2. Description of the Prior Art [0005]Microelectromechanical (MEMS) devices are finding ever-increasing areas of application in the modern economy as trends towards miniaturization, portability, lightweight, low power consumption and low cost drive many technologies. Sensors, actuators and many other devices are all affected by the wider application of microtechnology and MEMS fabrication techniques. [0006]The present invention relates to a floating MEMS device (FLEMS) in which a proof mass is levitated electrostatically as part of a MEMS device, without the need for feedback control means and, once levitated, without mechanical contact between the proof mass and any other portion of the device. [0007]This non-contact floating MEMS device of the present invention should be contrasted to prior MEMS devices, particularly accelerometers, in which acceleration is typically sensed by deflection of a proof mass mechanically coupled to the device. Examples include U.S. Pat. Nos. 5,969,848; 5,992,233; 6,067,858; 6,296,779 and 6,250,779. [0008]Electrostatic levitation has been used in a variety of non-MEMS fields of application including non-contact materials processing, acceleration or inertial sensors, and other applications. However, these devices typically require complex means to control and stabilize the position of the proof mass. For example, U.S. Pat. Nos. 5,015,906 and 5,187,399 employ high frequency sinusoidal excitation circuitry for levitation and control. U.S. Pat. No. 4,521,854 is an example of electrostatic levitation requiring a complex sensing and feedback system to maintain the proof mass in its floating position. [0009]In view of the foregoing, a need exists in the art for a floating MEMS device that includes self-stabilizing levitation without requiring sensing and/or feedback systems for controlling the levitation of the proof mass. SUMMARY OF THE INVENTION [0010]Accordingly and advantageously the present invention includes MEMS devices and applications thereof in which a proof mass is caused to levitate by electrostatic repulsion. [0011]The present invention relates to a floating MEMS device (FLEMS) in which a proof mass is levitated electrostatically without the need for feedback control means and, once levitated, without mechanical contact between the proof mass and any other portion of the device. This is in contrast with other MEMS devices, including accelerometers and inertial sensors, in which deflection of a mechanically-coupled proof mass, cantilevered beam or other structure is the basis for measuring acceleration. In various embodiments of the present non-contact floating MEMS device, mechanical wear is substantially eliminated and mechanical parasitic effects are sharply reduced or eliminated. Thus, an important objective of the present invention is to produce a floating MEMS device in which the proof mass has no mechanical contact with other portions of the device. [0012]Configurations of electrodes for a FLEMS device are described that, when charged with like charges as the proof mass, result in self-stabilized floating of the proof mass based upon electrostatic repulsion. Self-stabilization results from a FLEMS structure such that, when the proof mass is displaced from its equilibrium position, electrostatic forces arise tending to restore the proof to its equilibrium position. The magnitude of the restoring electrostatic forces tend to increase in magnitude as the proof mass undergoes a larger displacement from its equilibrium position. Thus, another objective of the present invention is to produce a self-stabilizing FLEMS device that does not require feedback control systems. In addition, since only like electrical charges are in close proximity, the dangers of short circuits are markedly reduced. [0013]Perturbations causing displacement of the proof mass can conveniently be measured by measuring the changes in electrical properties of the stabilization electrodes or electrical properties of the electrodes causing floating, and/or the electrical properties of additional sensing electrodes that can be included to further enhance sensing capabilities. Drive electrodes can also be included that allow forces to be applied to the charged proof mass resulting in a floating, electrically controllable MEMS device. Numerous applications are possible including: 1) Charge storage device. 2) GHz resonator. 3) Accelerometer. 4) Wide-angle scanner. 5) Magnetometer. 6) Nanogravity sensor. 7) Inertial navigation. 8) Magnetic confinement. 9) Quantum gyros. 10) Harsh-environment applications. 11) Thermal isolation applications. 12) Micro transport. [0014]FLEMS devices can conveniently be fabricated by lithographic technologies developed, in part, for the fabrication of integrated circuits. In addition, FLEMS devices can be fabricated by means of various three-dimensional microfabrication technologies that have been developed by several research groups and publicly available including EFAB.TM., PolyMUMPs, among others. [0015]Other embodiments of FLEMS devices include a proof mass attached to a plurality of side electrodes that carry a substantial portion of the electrostatic charge of the proof mass. The side electrodes can be terminated by one or more termination blocks or other structures that lead to stable levitation of the proof mass and attached side electrodes when this combined structure is embedded in a suitable configuration of stabilizing electrodes. [0016]The proof mass and the stabilizing electrodes can be charged by a variety of techniques including contact with an external voltage source, charging by means of electrification by induction and/or conduction, capacitance, tribocharging, electric discharge, among other methods. [0017]Once charged FLEMS, devices typically require almost no additional electric power, depending on the magnitude of leakage currents for the structures and materials used in the FLEMS device and for the environmental conditions in which it is operated. That is, it is not required to maintain continuous contact between the charging source and the stabilizing electrodes. The charging source can be disconnected and re-engaged only when necessary to replenish the charge that is lost over time due to leakage. [0018]Further, the operating range of FLEMS devices is, or can be made, very large. The response of a FLEMS device to various external perturbations can be changed by changing the amount of electric charge residing on various portions of the FLEMS device, including dynamic changes in real-time or near real-time during operation of the device. In addition, FLEMS devices are typically largely insensitive to operating temperatures. [0019]These and other advantages are achieved in accordance with the present invention as described in detail below. BRIEF DESCRIPTION OF THE DRAWINGS [0020]To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The drawings are not to scale and the relative dimensions of various elements in the drawings are depicted schematically and not to scale. Continue reading... Full patent description for Self-stabilizing, floating microelectromechanical device Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Self-stabilizing, floating microelectromechanical device patent application. Patent Applications in related categories: ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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