SELF ENERGIZED WIRELESS MEMS DEVICES

Abstract: A wireless, remote sensor is implemented by integrating a MEMS sensor, an energy harvesting/storage MEMS, a transceiver MEMS and a miniature antenna. A low charge of energy, created by vibratory, heat or chemical action, in the micro-watt range, is generated and stored by the harvesting/storage MEMS for powering the combined MEMS device. A central monitoring station signals the MEMS transceiver to transmit any data acquired by the MEMS sensor. Power is provided by the harvesting/storage MEMS to transmit data, obtained by the sensor, via the miniature antenna to the central monitoring station. Transmitting time is very short, requiring little power, and the transceiver is only activated by a signal from the monitoring station.

Description: SELF ENERGIZED WIRELESS MEMS DEVICES BACKGROUND OF THE INVENTION 1. Technical Field: The present invention generally relates to miniature electro-mechanical devices and in particular to MicroElectroMechanical Systems (MEMS). Still more particularly, the present invention relates to combining a plurality of MEMS each having different functions. 2o Description of the Related Art: MEMS are very small devices that combine electrical and mechanical components. Generally, the size of MEMS vary from as large as a few millimeters to much smaller. MEMS can be made extremely small, so small in fact that hundreds of the devices can fit in the same space as a single non-MEMS that performs the same function. MEMS are fabricated, usually, using integrated circuit processing methods and depending on the structure, hundreds to thousands of these devices can be fabricated on a single wafer. An example of a MEMS device is a micro-circuit that is Texas Instruments' Digital MicroMirror Device™ (DMD) which uses extremely tiny movable mirrors to reflect light. The mirrors develop a digital image by rapidly switching on or off according to logic programming. A light beam then reflects the digital image off the DMD's surface. The digital images are generated and may then be projected onto a surface for viewing. Currently, there are individual MEMS devices that are capable of storing an electrical charge. There are proposed power harvesting MEMS devices that utilize heat, mechanical or chemical environments to produce electrical power. Other MEMS devices are in development that are capable of transmitting signals and still more devices that sense and measure inputs. There are MEMS devices that are capable of receiving, storing and performing programmable functions, but all utilize a power source with at limited life span. There are no self-sustaining MEMS wireless sensors without energy source replacement requirements. It would therefore be desirable to provide an apparatus and method for combining a power source, a sensing element and a transmitting/receiving function in a single MEMS device for remote, self-sustaining and automatic monitoring. SUMMARY OF THE INVENTION A wireless, remote sensor is implemented by integrating a MEMS sensor, an energy harvesting/storage MEMS, a transceiver MEMS and a miniature antenna. A low charge of energy, created by vibratory, heat or chemical action, in the micro-watt range, is generated and stored by the harvesting/storage MEMS for powering the combined MEMS device. A central monitoring station signals the MEMS transceiver to transmit any data acquired by the MEMS sensor. Power is provided by the harvesting/storage MEMS to transmit data, obtained by the sensor, via the mimature antenna to the central monitoring station. Transmitting time is very short, requiring little power, and the transceiver is only activated by a signal from the monitoring station. The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 depicts a high-level block diagram of a self-powered MEMS device in which a preferred embodiment of the present invention may be implemented; Figure 2 illustrates an embodiment wherein self-powered MEMS devices are utilized in an aircraft, in accordance with a preferred embodiment of the present invention; Figure 3 depicts an installation of a self-powered MEMS device in an aircraft, in accordance with a preferred embodiment of the present invention; and Figure 4 is an application of self-powered MEMS devices for monitoring the human body, in accordance with a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference now to the figures, and in particular with reference to Figure 1, a high-level block diagram of a micro-electro-mechanical system device in which a preferred embodiment of the present invention may be implemented is depicted. The present invention comprises a combination of MEMS devices to provide a self-powered, sensing and signaling mechanism. In this embodiment, self-powered sensor 100 is depicted with MEMS sensor 102, MEMS energy harvesting/storage device 104, MEMS transceiver 106 and miniature antenna 108. MEMS sensor 102 may sense heat, cold, vibration, etc. Interfaces 103 and 105 are formed at the boundaries between sensor 102 and energy harvesting device 104, and between energy harvesting/storage device 104 and transceiver 106. Communication is achieved between the individual MEMS devices that make up self-powered sensor 100 through the use of the interfaces. Energy harvesting/storage device 104 may be based on energy provided by mechanical, chemical, heat, solar, etc., means. In this embodiment, the energy harvesting/storage device 104 converts mechanical energy to electrical energy using a piezoelectric or electro-strictive device which converts vibration or mechanical energy, to electrical energy. This electrical energy is then made available to both sensor 102 and transceiver 106 via the respective interfaces 103 and 105. The energy is made available only for a short period of time and at a low energy level - generally measured in micro-watts. As the device is usually in constant mechanical stress, the harvesting device is constantly charging. In an environment with a high rate of mechanical motion such as in an aircraft, mechanical energy is easy to tap because of the vibration caused by the aircraft engines and wind stresses. Effectively, the harvesting MEMS 104 may be constantly producing electrical power during operation of the aircraft because energy harvesting/storage device 104 is constantly being stressed. This power is made available to sensor 102 and transceiver 106. Specific parameters are measured by sensor 102 and passed to transceiver 106 which then transmits the data, utilizing antenna 108, to a central receiving station (not shown) for processing. Referring to Figure 2, an application, utilizing self-powered MEMS sensors in an aircraft, in accordance with a preferred embodiment of the present invention is illustrated. Aircraft 200 is manufactured with conventional sensing devices installed in specific locations throughout the aircraft. The sensors are connected, utilizing wiring harnesses, to a central receiver that provides the incoming sensor data to recording and processing devices. However, after the aircraft is delivered and in service, problems occur that may have been unforeseen during the design stage. For instance, a problem may occur that requires MEMS sensor 204 being located in the tail of the aircraft to monitor the j ackscrew (for raising and lowering tail flaps). Normally, a periodic visual inspection by maintenance workers would be required. There is likely no wiring harness available to tap, in order to send a sensor signal back to a central receiver. The present invention may be installed in the tail in an appropriate position to monitor the jack screw, to provide the required data to central transceiver 202 without the need for an additional wiring harness. Also, the location of MEMS sensor 204 may be too far from central transceiver 202, so the signal may be transferred by relay antenna 208. MEMS sensors and relay antennas may be located around the aircraft for detecting and transmitting required information. MEMS sensor 204 can be used to detect internal aircraft temperatures. MEMS sensor 210 can be used to detect engine temperature or vibrations. MEMS 212 can be used to sense stress in fuel tank walls. In other words MEMS devices, in the manner of the present invention, can be substituted for hard wired sensors in virtually any situation. Additionally, there is no need to go to the expense and effort of providing wiring harnesses to the devices as there would be with normal sensors for any new aircraft design and construction. Referring now to Figure 3, an installation of a self-powered MEMS device in an aircraft in accordance with a preferred embodiment of the present invention, is depicted. A cross-section of aircraft skin 220, with interior cavity 221, is shown. Installed on the interior of surface 220 is self-powered MEMS device 224. The sensor portion of self- powered MEMS device 224 is mounted directly to aircraft skin 220 for sensing stress in the skin. The energy harvesting portion of self-powered MEMS device 224 converts mechanical energy (aircraft skin vibrations) to electrical energy which powers the sensor portion and the transceiver portion of sensor 224. Signals are generated and transmitted through the antenna to relay antenna 226, which then relays the signal to central transceiver 202. As described in Figure 2, self powered MEMS sensors may be placed in virtually any location on the aircraft. The present invention utilizes the environment, through surface vibration, to power the sensing and transmitting sections of the self- powered MEMS device. Central transceiver 202 can poll all the self-powered MEMS devices installed on the aircraft. When the device receives a polling signal, power generated by the energy harvesting portion of the device is provided to the sensor and transceiver. Since the power is always present during operation of the aircraft, due to constant vibration, the power is available and power storage is not particularly necessary for this application. The sensor communicates the sensed data to the transceiver portion of the MEMS device. The transceiver then transmits the data to central transceiver 202 via relay antenna 226. Remote applications are one of the problems solved by the present invention. All problems relating to locations that are difficult to monitor, locations with no wiring available, hazardous locations, etc., are easily solved by self-powered MEMS devices. Other locations that are hard or dangerous to monitor with standard sensing devices include monitoring devices for the human body. Wireless sensors for human body monitoring are operated the same as the MEMS sensors on the aircraft except, in addition to ambient energy conversion, energy creation may be provided by magnetic resonance charging. Referring to Figure 4, an application of self-powered MEMS devices for monitoring the human body, in accordance with a preferred embodiment of the present invention, is depicted. Human body 300 may be monitored by implanting MEMS devices 302 in strategic locations for detecting specific actions by the body. Conventional implanted devices can be a source of infection especially if the device is large or has wires for attaching to the external monitoring device. Connectors and wiring inside the human body are a major cause of infection. Fissures periodically form at the interface between the passages through the skin and the skin tissue, through which microorganisms can enter and infect the body. The intrusions can result from various movements of the body which exert transient tensile and compressive forces on the passages by which the implants pass through the skin. Additionally, a device that uses a battery, generally requires that the battery be surgically replaced periodically, providing yet another source of infection and trouble. A MEMS device combining a MEMS energy harvesting and storage device, a MEMS sensing device and a MEMS tranceiver can be enclosed in a non-reactive coating for implantation in the human body. By implanting and completely enclosing the extremely small monitoring device, risk of infection is reduced. Constant monitoring of the device may be accomplished by providing a portable data collector/storage device 306 worn on the body. The power required for transmission of data is minimal. Since the distance to the receiving collector/storage device is small, an implanted MEMS device 302 can generally generate enough power on its own. One method for generating the required power can be converting heat generated by a normal body temperature of 98.6 degrees. The amount generated may be small, but the need is small, because power is only used when the device is polled by the external collector/storage device. However, external charging device 304 may be used to charge MEMS device 302 when the power source is a non-pathogenic re-chargeable MEMS device. The MEMS device can also have a programmable circuit included for preprocessing collected data. Self-powered MEMS devices allow maximum flexibility in placing the sensors and are not tied to power replacement requirements or wiring constraints. For instance, a device for monitoring pulse rate or blood pressure may be located next to an artery or a blood vessel. A mechanical energy conversion device, e.g., piezoelectric, may be used to power the sensor and transceiver, by locating the MEMS device on a muscle. The sensor can measure body fluids makeup using microcircuits that sense chemicals. A MEMS device that includes an energy harvesting MEMS and a transceiver MEMS is versatile. In the illustrated embodiments, the energy harvesting MEMS converts mechanical, heat or chemical energy to a low electrical energy charge. The energy is in the microwatt range and signal transmission is in the form of a burst signal and is around one millisecond. Storage time of the charge is about 99 milliseconds and the transceiver is only activated when a coded signal is received from a data collection station. The energy harvesting MEMS is constantly charging and storing electrical power, so the data is always able to be transmitted when polled. The transmitted data pulses from the MEMS device are in the nanometer wavelength range. Miniature relay antennas used on inanimate objects can be located to relay remote data pulses. In the case of MEMS devices utilized in a human body, relay antennas may not be needed unless the body is in a remote location relative to a receiving monitor. A relay antenna can be strategically located to automatically relay the vital data to a remote transmitter. The transmitter can then transmit the data to a health facility. While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims: CLAIMS: What is claimed is: 1. An apparatus for momtoring and transmitting parameters of, and proximate an object, comprising: a MEMS power harvesting and storage device; a MEMS transceiver interfaced with said MEMS harvesting and storage device; a MEMS sensor interfaced with said MEMS transceiver and said MEMS power harvesting and storage device; an antenna connected to said transceiver for receiving and transmitting signals; and an enclosure for said MEMS devices. 2. The apparatus of claim 1, further comprising: a programmable circuit for processing input from said sensor. 3. The apparatus of claim 1, wherein said power harvesting and storage device converts kinetic energy to electrical power. 4. The apparatus of claim 1, wherein said power harvesting and storage device alternatively comprises a battery. 5. The apparatus of claim 1, wherein said power harvesting and storage device comprises a converts heat energy to electrical power. 6. The apparatus of claim 1 , wherein said MEMS sensor measures a specific aircraft parameter. 7. The apparatus of claim 1, wherein said MEMS sensor measures mechanical parameters. 8. The apparatus of claim 1, wherein said MEMS sensor measures electrical parameters. 9. The apparatus of claim 1, wherein said MEMS sensor measures chemical parameters. 10. A medical device for monitoring body functions, comprising: a MEMS power harvesting and storage device; a MEMS transceiver interfaced with said MEMS harvesting and storage device; a MEMS sensor interfaced with said MEMS transceiver and said MEMS power harvesting and storage device; an antenna connected to said transceiver for receiving and transmitting signals; and a material conducive to long term implantation in a human body completely enclosing said power source, said transceiver, said sensor and said antenna. 11. The apparatus of claim 10, further comprising: a programmable circuit for processing input from said MEMS sensor. 12. The apparatus of claim 10, wherein said power harvesting and storage device converts kinetic energy to electrical power. 13. The apparatus of claim 10, wherein said power harvesting and storage device alternatively comprises a battery. 14. The apparatus of claim 10, wherein power harvesting and storage device converts heat energy to electrical power. 15. The apparatus of claim 10, wherein said MEMS sensor measures a specific body function. 16. A method for transmitting information detected by a sensor from an isolated location, comprising the steps of: providing a MEMS power harvesting and storage device; interfacing a MEMS transceiver with said MEMs power harvesting and storage device interfacing a MEMS sensor with said MEMS power harvesting and storage device and said MEMS transceiver; connecting an antenna to said MEMS transceiver for transmitting and receiving data; and combining said MEMS power harvesting and storage device, said MEMS sensor, said MEMS transceiver and said antenna into a single unit. 17. The method of claim 16, further comprising the step of: processing input from said sensor. 18. The method of claim 16, further comprising the step of: converting kinetic energy to electrical converter. 19. The method of claim 16, furhter comprising the step of: providing power for the combination MEMS unit utilizing a charge storing MEMS device. 20. The method of claim 16, further comprising: converting heat energy to electrical power. 21. An apparatus adapted to be attached to an aircraft for monitoring and transmitting targeted parameters of said aircraft comprising a combination of MEMS devices, including: a MEMS power harvesting and storage device; a MEMS transceiver interfaced with said MEMS harvesting and storage device; a MEMS sensor interfaced with said MEMS transceiver and said MEMS power harvesting and storage device; an antenna connected to said transceiver for receiving and transmitting signals; and material for enclosing said combination of MEMS devices appropriate to the environment in which said combination will be installed. 22. The apparatus of claim 21 , further comprising: a relay antenna for relaying signals from said MEMS transceiver. 23. The apparatus of claim 21 , further comprising : a central receiver for processing said signals from said apparatus. 24. The apparatus of claim 21, wherein said MEMS sensor measures engine heat. 25. The apparatus of claim 21, wherein said MEMS sensor measures mechanical vibration. 26. The apparatus of claim 2 , wherein said MEMS sensor measures tail flap position.

Inventors: WANG SHENG T, WANG, SHENG, T.
Applicants: LOCKHEED CORP, LOCKHEED MARTIN CORPORATION
Application year: 2001
Main classification: A61B5
IPC codes: A61B5