Power plants – Motor operated by expansion and/or contraction of a unit of... – Mass is a solid
Reexamination Certificate
2000-04-05
2002-03-26
Nguyen, Hoang (Department: 3748)
Power plants
Motor operated by expansion and/or contraction of a unit of...
Mass is a solid
C060S527000, C310S306000, C310S307000
Reexamination Certificate
active
06360539
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to microelectromechanical systems (MEMS), and more specifically to MEMS actuators.
BACKGROUND OF THE INVENTION
Microelectromechanical systems (MEMS) have been developed as alternatives to conventional electromechanical devices, such as relays, actuators, valves and sensors. MEMS devices are potentially low-cost devices, due to the use of microelectronic fabrication techniques. New functionality also may be provided, because MEMS devices can be much smaller than conventional electromechanical devices.
Many applications of MEMS technology use MEMS actuators. These actuators may use one or more beams that are fixed at one or both ends. These actuators may be actuated electrostatically, magnetically, thermally and/or using other forms of energy.
A major breakthrough in MEMS actuators is described in U.S. Pat. No. 5,909,078 entitled Thermal Arched Beam Microelectromechanical Actuators to the present inventor et al., the disclosure of which is hereby incorporated herein by reference. Disclosed is a family of thermal arched beam microelectromechanical actuators that include an arched beam which extends between spaced apart supports on a microelectronic substrate. The arched beam expands upon application of heat thereto. Means are provided for applying heat to the arched beam to cause further arching of the beam as a result of thermal expansion thereof, to thereby cause displacement of the arched beam.
Unexpectedly, when used as a microelectromechanical actuator, thermal expansion of the arched beam can create relatively large displacement and relatively large forces while consuming reasonable power. A coupler can be used to mechanically couple multiple arched beams. At least one compensating arched beam also can be included which is arched in a second direction opposite to the multiple arched beams and also is mechanically coupled to the coupler. The compensating arched beams can compensate for ambient temperature or other effects to allow for self-compensating actuators and sensors. Thermal arched beams can be used to provide actuators, relays, sensors, microvalves and other MEMS devices. Thermal arched beam microelectromechanical devices and associated fabrication methods also are described in U.S. Pat. No. 5,955,817 to Dhuler et al. entitled Thermal Arched Beam Microelectromechanical Switching Array; U.S. Pat. No. 5,962,949 to Dhuler et al. entitled Microelectromechanical Positioning Apparatus; U.S. Pat. No. 5,994,816 to Dhuler et al. entitled Thermal Arched Beam Microelectromechanical Devices and Associated Fabrication Methods; and U.S. Pat. No. 6,023,121 to Dhuler et al. entitled Thermal Arched Beam Microelectromechanical Structure, the disclosures of all of which are hereby incorporated herein by reference in their entirety.
As MEMS actuators continue to proliferate and to be used in more applications and environments, it would be desirable to allow the displacement and/or force of MEMS actuators to be controlled over wider ranges. Unfortunately, due to the scale of MEMS actuators, only a limited range of displacement and/or force may be obtainable.
A publication entitled Bent-Beam Electro-Thermal Actuators for High Force Applications by Que et al., IEEE MEMS '99 Proceedings, pp. 31-36, describes in-plane microactuators fabricated by standard microsensor materials and processes that can generate forces up to about a milli-newton. They operate by leveraging the deformations produced by localized thermal stresses. It is also shown that cascaded devices can offer a four times improvement in displacement.
Notwithstanding these improvements, there continues to be a need for MEMS actuators that can provide wider ranges of displacement and/or force for various actuator applications.
SUMMARY OF THE INVENTION
Microelectromechanical actuators according to embodiments of the invention include a substrate, spaced apart supports on the substrate and a thermal arched beam that extends between the spaced apart supports and that further arches upon heating thereof, for movement along the substrate. A plurality of driven arched beams are coupled to the thermal arched beam. The end portions of the respective driven arched beams move relative to one another to change the arching of the respective driven arched beams in response to the further arching of the thermal arched beam, for movement of the driven arched beams. A respective driven arched beam also includes a respective actuated element at an intermediate portion thereof between the end portions, wherein a respective actuated element is mechanically coupled to the associated driven arched beam for movement therewith, and is mechanically decoupled from the remaining driven arched beams for movement independent thereof. By allowing independent movement of the actuated elements, a variety of actuator applications may be provided wherein it is desired to actuate multiple elements in the same or different directions.
For example, in first embodiments, the plurality of driven arched beams comprise first and second driven arched beams that extend parallel to one another, such that the actuated elements that are mechanically coupled to the first and second driven arched beams move in a same direction by the further arching of the thermal arched beam. In other embodiments, the first and second arched beams arch away from each other, such that the actuated elements that are coupled to the first and second driven arched beams move in opposite directions by the further arching of the thermal arched beam. In yet other embodiments, the first and second driven arched beams arch toward one another, such that the actuated elements that are mechanically coupled to the first and second driven arched beams move in opposite directions by the further arching of the thermal arched beam.
In other embodiments, the respective end portions are squeezed together by the further arching of the thermal arched beam, to thereby increase arching of the driven arched beam. In alternate embodiments, the end portions are pulled apart by the further arching of the thermal arched beam, to thereby decrease arching of the driven arched beams.
In yet other embodiments, the thermal arched beam includes an intermediate portion between the end portions, and the driven arched beams include intermediate portions between the respective end portions thereof. The intermediate portions of the thermal arched beams are coupled to one of the end portions of the driven arched beams. In first embodiments, the intermediate portion of a second thermal arched beam is coupled to the other of the end portions of the driven arched beams. An H-shaped microelectromechanical actuator thereby is formed, wherein each leg of the H comprises a thermally activated arched beam, and the cross-members of the H comprises mechanically activated driven arched beams. In second embodiments, an anchor is provided that anchors the other end portions of the driven arched beams to the substrate. Thus, only one end of the driven arched beams is driven by a thermal arched beam actuator. These embodiments thereby form microelectromechanical actuators having a T-shape, wherein the cross-member of the T comprises a thermally activated arched beam and wherein the leg of the T comprises mechanically activated arched beams.
In other embodiments of microelectromechanical actuators according to the present invention, the thermal arched beam extends between the spaced apart supports along a first direction on the substrate, and further arches upon heating thereof, for movement along the substrate in a second direction that is orthogonal to the first direction. The driven arched beams extend along the substrate in the second direction and the arching of the driven arched beams is changed in the first direction by the further arching of the thermal arched beam for movement along a substrate in the first direction.
In yet other embodiments, second spaced apart supports are provided on the substrate, and a second thermal arched beam is provided that extends between the second spaced a
Cowen Allen B.
Dhuler Vijayakumar R.
Hill Edward A.
Mahadevan Ramaswamy
Wood Robert L.
JDS Uniphase Corporation
Myers Bigel & Sibley & Sajovec
Nguyen Hoang
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