Power plants – Motor operated by expansion and/or contraction of a unit of... – Mass is a solid
Reexamination Certificate
2002-01-31
2004-01-20
Richter, Sheldon J. (Department: 3748)
Power plants
Motor operated by expansion and/or contraction of a unit of...
Mass is a solid
C060S528000, C310S306000
Reexamination Certificate
active
06679055
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to handling of micron scale structures using micro-devices, and more particularly to a system and method for multi-axis controlled translation and rotation of microcomponents using electrothermal microactuators.
Extraordinary advances are being made in micromechanical device and microelectronic device technologies. Further, advances are being made in MicroElectroMechanical Systems (“MEMS”), which incorporate integrated micromechanical and microelectronic devices and components. The term “microcomponent” is used herein generically to encompass microelectronic components, micromechanical components, as well as MEMS components, each generally having at least one dimension in the range between approximately 0.1 micron and 1000 microns. Advances in microcomponent technology have resulted in an increasing number of microcomponent applications. For example, various microcomponents are fabricated and then assembled together. That is, post-fabrication assembly operations may be performed on microcomponents to form devices that may have greater utility.
Accordingly, a need often arises for performing handling tasks for assembling microcomponents. For example, a microcomponent may need to be translated from one position to another position, such that the microcomponent can be presented for assembly together with another microcomponent. As another example, a microcomponent may need to be rotated in some manner such that it is properly oriented for assembly together with another microcomponent. For micro-optical technologies it may be desired to provide controlled movement of a lens with respect to a light source, such as a laser emitter, to produce desired light emission patterns. Similarly, it may be desired to provide controlled movement of an optical fiber end in order to properly interface with a light source.
Because of the small size of microcomponents, handling them to perform such assembly-related tasks is often complex. Due to scaling effects, forces that are insignificant at the macro scale become dominant at the micro scale (and vice versa). For example, when parts to be handled are less than one millimeter in size, adhesive forces can be significant compared to gravitational forces. These adhesive forces arise primarily from surface tension, van der Waals, and electrostatic attractions and can be a fundamental limitation to handling of microcomponents. (See e.g., “A survey of sticking effects for micro parts handling,” by R. S. Fearing,
Proc. IEEE/RSJ Int. Conf. on Intelligent Robots and Systems
, Vol. 2, pp. 212-217, Pittsburgh, Aug. 5-9, 1995; “Hexsil tweezers for teleoperated microassembly,” by C. G. Keller and R. T. Howe,
IEEE Micro Electro Mechanical Systems Workshop
, Nagoya, Japan, Jan. 26-30, pp. 72-77, 1997; and “Microassembly Technologies for MEMS,” by Michael B. Cohn, Karl F. Böhringer, J. Mark Noworolski, Angad Singh, Chris G. Keller, Ken Y. Goldberg, and Roger T. Howe, Proc.
SPIE Micromachining and Microfabrication
, pp. 216-230, 1998.)
Also, relatively precise movement (e.g., translational and/or rotational movement) of a microcomponent is often required to perform assembly operations. Consider, for example, that in some cases mishandling of a part resulting in misalignment of only a few microns may be unacceptable, as the microcomponent to which the part is to be coupled may be only tens of microns in total size, and the portion of the microcomponent that is to be engaged for coupling may be even smaller. Thus, microcomponents present particular difficulty in handling for performing assembly operations.
Traditionally, a high-precision, external robot is utilized for handling of microcomponents to perform assembly operations. For instance, a high-precision, external robot having three degrees of translational freedom (e.g., capable of translating along three orthogonal axes X, Y, and Z) and having three degrees of rotational freedom may be used for handling microcomponents to perform assembly operations. For example, PolyTec PI manufactures a five degree of freedom robotic system specifically designed for high precision assembly of fiber optic modules. However, such external robots are generally very expensive. Additionally, external robots typically perform microcomponent assembly in a serial manner, thereby increasing the amount of time required for manufacturing micro-devices. That is, such robots typically handle one microcomponent at a time, thereby requiring a serial process for assembling microcomponents together.
Accordingly, MEMS systems have been developed to provide translation of a specimen in particular directions. For example, micro-translation systems have been developed in which a microcomponent stage, upon which a specimen may be placed or mounted, is operatively coupled to an actuator to provide controlled movement of the stage and, accordingly, translation of the specimen. Multiple actuators may be disposed in such a micro-translation system to provide a configuration in which motion in multiple directions may be provided, such as along both the X and Y axes.
In the prior art, bimorph actuators or thermal bimorph actuators generally move laterally in a plane of motion of the actuator. Surface micro-machined polysilicon thermal actuators and arrays traditionally have a hot arm and a cold arm. The hot arm is typically thinner and therefore more resistive than the cold arm. When passing electric current through those two arms in series, the hot arm due to its higher resistance heats and expands more than the cold arm, causing the free end of the actuator to move in an arcing motion.
“Applications for Surface-Micromachined Polysilicon Thermal Actuators and Arrays” by Comtois and Bright, Sensors and Actuators A 58, pp. 19-25, 1997, and “Electrothermal actuators fabricated in four-level planarized surface micromachined polycrystalline silicon,” by Comtois et al., Sensors and Actuators A 70, pp. 23-31, 1998, describe thermal bimorph actuators having hot and cold arms, that provide motion only in a single direction along a single axis. “Automated Assembly of Flip-Up Micromirrors,” by Reid et al., 1997 International Conference on Solid-State Sensors and Actuators, Chicago, pp. 347-330, June 1997, describes a “back-bending” capability, such that the material of the hot arm reflows and shortens when pressed down towards a substrate at high temperature during the heating cycle, causing the actuator to bend in the opposite direction away from the substrate during a subsequent cooling cycle. U.S. Pat. No. 6,275,325/B1 (hereafter the '325 patent) issued Aug. 14, 2001, describes an actuator that can move in one direction along one axis. Instead of thinning the hot arm to increase electrical resistance, the cold arm includes a metallic layer that reduces electrical resistance. Multiple actuators of this type are coupled to a stage, for example four actuators, which can then lift the stage along the Z axis and/or rotate it about any combination of the X and Y axes.
U.S. Pat. No. 5,909,078 (hereafter the '078 patent), issued Jun. 1, 1999, describes various single direction thermal actuators known as thermal arch beam actuators.
U.S. Pat. No. 5,962,949 (hereafter the '949 patent), issued Oct. 5, 1999, describes an apparatus that can produce XYZ motion in three orthogonal directions by cascading three thermal arch beam actuators. The '949 patent describes two substantially identical single direction actuators independently driving a stage along the X and Y axes. A third actuator producing upward Z motion is embedded in the stage.
U.S. Pat. No. 5,870,007 (hereafter the '007 patent), issued Feb. 9, 1999, describes a set of bimorph actuators that are coupled to a stage, which they can move in multiple directions. Each individual actuator has a “meander cantilever” configuration and provides motion only in one direction. A single actuator is not capable of both in-plane and out-of-plane motion. To move the stage in multiple directions requires multiple actuators.
It is possible to de
Haynes and Boone LLP
Richter Sheldon J.
Zyvex Corporation
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