Compositions – Piezoelectric
Reexamination Certificate
2001-11-28
2004-02-10
Koslow, C. Melissa (Department: 1755)
Compositions
Piezoelectric
C252S500000, C252S501100, C310S311000, C310S330000
Reexamination Certificate
active
06689288
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electroactive polymeric materials. More particularly, it relates to a new class of polymeric blends for sensor and actuation dual functionality.
2. Description of the Related Art
Sensors and actuators are widely demanded in many technologies to realize precise control of mechanical motion in mechanical, electronic and optical, as well as electro-optical and electromechanical devices. Miniaturization and intellectualization of these devices requires multifunctional materials for simple processing and low cost. Intelligent structures and systems are very important in flight safety and efficiency of aerospace crafts. As a core technology in the intelligent structure and systems, microelectromechanical systems (MEMS) are composed of micro-scale mechanical sensors and actuators. Presently, sensor materials and actuator materials are chosen as separate individual materials for the processing of MEMS.
U.S. Pat. No. 6,239,534 describes a piezoelectric/electrostrictive device. This device, however, requires extensive mechanical manipulation. Specifically, it requires a substrate having two pairs of concave recesses, a connection plate, fixing plate and piezoelectric/electrostrictive elements.
U.S. Pat. No. 6,232,702 describes an electroactive device. This device also has burdensome mechanical requirements. This device requires a ceramic annular substrate having a pair of opposed planar annular surfaces, a hollowed interior region and a thickness aspect.
The new sensor-actuation dual functional polymeric blends described herein provide an enabling electroactive polymer for simplification of processing for MEMS and other electromechanical and electro-optical devices; therefore, the cost of the devices can be significantly reduced.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide what is not available in the art, viz., an electroactive polymeric material which provides both sensing and actuation functionality.
It is another object of the present invention to provide a material having temperature invariant piezoelectric response over a range of temperatures.
It is another object of the present invention to provide a material having excellent piezoelectric properties and sensing capability.
It is yet another object of the present invention to provide a material having a large electric field induced strain that significantly increases the range of the electrically-controlled mechanical motion.
Another object of the present invention is to provide a material having excellent processability that makes the material properties tailorable for specific requirements in applications.
Yet another object of the present invention is to provide a lightweight dual-functionality material.
Still another object of the present invention is to provide a material with high power density resulting in reduced energy consumption.
Another object of the present invention is to provide conformable, flexible actuation material that will enable the design for new types of actuators.
Yet another object of the present invention is to provide a two-phase system with adjustable-composition and morphology to optimize mechanical, electrical, and electromechanical properties.
These primary objects, and other attending benefits, are achieved by the present invention. The invention described herein supplies a new class of electroactive polymeric blend materials which offer both sensing and actuation dual functionality. The blend comprises two components, one component having a sensing capability and the other component having an actuating capability. These components should be co-processable and coexisting in a phase separated blend system. Specifically, the materials are blends of a sensing component selected from the group consisting of ferroelectric, piezoelectric, pyroelectric and photoelectric polymers and an actuating component that responds to an electric field in terms of dimensional change. Said actuating component includes, but is not limited to, electrostrictive graft elastomers, dielectric electroactive elastomers, liquid crystal electroactive elastomers and field responsive polymeric gels. The sensor functionality and actuation functionality are designed by tailoring the relative fraction of the two components. The temperature dependence of the piezoelectric response and the mechanical toughness of the dual functional blends are also tailored by the composition adjustment. Since the dual functional blends contain two components, the electric, mechanical, and electromechanical properties of the blends are controlled by the following design parameters: molecular synthesis of sensing polymers and actuating polymers for the blends; selection of the sensing component and actuating components for blends; variation of the fraction of the two component polymers; morphology control of the two components by designed processing routes.
Commercial applications for self-sensing actuation materials include electromechanical transdusors/actuators that can be used in surface flow dynamics control, precise position control, vortex generators in flow control, optical switching, optical filtering, and vibration suppression. These and other actuation applications could benefit from these materials as they will allow simultaneous sensing and actuation capability.
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J. Su et al, “Electromechanically Active Polymer Blends for Actuation,” Electroactive Polymer Actuators and Devices (EAPAD), SPIE-The International Society of Optical Engineering (Newport Beach, USA), p. 65-72, (Mar. 6, 2000).
Harrison Joycelyn S.
Ounaies Zoubeida
St. Clair Terry L.
Su Ji
Edwards Robin W.
The United States of America as represented by the Administrator
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