Scott H. Goodwin-Johansson

Integrated force arrays

Integrated force arrays (IFAs), which are flexible metallized membranes that can be patterned using the techniques of VLSI electronics and that undergo substantial deformation when voltage is applied, have been developed. They may be configured as macroscopic actuators or used in highly articulated systems of great complexity. The theory of operation, the methods of construction, and the observational results for IFA test structures are presented.<<ETX>>

Active noise supressors and methods for use in the ear canal

A noise suppressor includes an input transducer and an output transducer adapted to be located in an ear canal. A housing is provided to support the transducers in the ear canal, and the housing provides an acoustically unobstructed passage from the entrance of the ear canal to the ear drum. The input transducer generates electrical signals in response to sound pressure waves entering the ear canal, and a portion of the electrical signal is processed to generate an inverse noise signal which is applied to the output transducer. Accordingly, the output transducer produces inverse noise pressure waves in order to reduce an undesired noise portion of the sound pressure waves reaching the ear drum. The sound pressure waves also reach the ear drum without significant alteration.

Integrated force arrays: theory and modeling of static operation

Integrated force arrays (IFAs) are a novel means of microelectromechanical actuation. They are membranes that consist of thousands of micron-scale deformable capacitors and are capable of contraction and force exertion in one dimension by application of an applied voltage. The theory and modeling of the static operation of a representative unit device and an array is presented. The electrostatic and elastic forces present in the system are considered and classical beam theory and superposition are applied to calculate the voltage-induced closure and force generation of the networks without the aid of finite element analysis. It is shown that contraction and force generation are expected at reasonable voltages for these modular structures: Ideal system contraction on the order of 40% is possible and minimum external forces of 4500 /spl mu/N/mm/sup 2/ are expected with the application of 50 V. >

Intracardiac ultrasound catheter using a micromachine (MEMS) actuator

Catheter based intracardiac ultrasound offers the potential for improved guidance of interventional cardiac procedures. The objective of this work is the development of catheter based, forward-looking mechanical sector scanners incorporating high frequency ultrasound transducers operating at frequencies up to 20 MHz. The current transducer assembly consists of a single 20 MHz PZT piston mounted on a polyimide table that pivots on gold plated polyimide hinges. This table-mounted transducer is tilted using a linear MEMS actuator to produce a sector scan. The prototype transducer/actuator assembly was fabricated and interfaced with a personal computer to create a single channel ultrasound scanner. This paper discusses the development of and results obtained by this real time scanning system.

Reduced voltage artificial eyelid for protection of optical sensors

The fabrication, testing and performance of a new device for the protection of optical sensors will be described. The device consists of a transparent substrate, a transparent conducting electrode, insulating polymers, and a reflective top electrode layer. Using standard fabrication techniques, arrays of apertures can be created with sizes ranging from micrometers to millimeters. A stress gradient resulting from different coefficients of thermal expansion between the top polymer layer and the reflective metal electrode, rolls back the composite thin film structure from the aperture area following the chemical removal of a release layer, thus forming the open condition. The application of a voltage between the transparent conducting and reflective metal electrodes creates an electrostatic force that unrolls the curled film, closing the artificial eyelid. Fabricated devices have been completed on glass substrates with indium tin oxide electrodes. The curled films have diameters of less than 100micrometers with the arrays having fill factor transparencies of over 70%. Greater transparencies are possible with optimized designs. The electrical and optical results from the testing of the artificial eyelid will be discussed.

Integrated force array: interface to external systems

Integrated Force Arrays (IFAs) are thin film linear actuators which operate with substantial displacement and force. The methods of attachment of these devices to external systems are under development. Our current methods to incorporate IFAs in an scanning ultrasound imaging systems as well as a new material and method for attachment will be described.

Integrated force array: positioning drive applications

Integrated Force Arrays (IFAs) are thin film membrane actuators that act as transfer devices for electrostatic force. They are capable of large amplitude motion and evidence significant energies per unit volume (eg. 8.2 erg/mm3). Devices which use IFAs as drivers to scan PZT acoustic imaging transducers are under development and will be discussed here.

High speed, large motion electrostatic artificial eyelid

The fabrication, testing and performance of a new device for the protection of optical sensors are described. The device consists of a transparent substrate, a transparent conducting electrode, insulating polymers, and a reflective top electrode layer. Using standard fabrication techniques, arrays of apertures can be created with sizes ranging from micrometers to millimeters. A stress gradient resulting from different thermal coefficients of expansion between the top polymer layer and the reflective metal electrode, rolls back the composite thin film structure from the aperture area following the chemical removal of a release layer. The application of a voltage between the transparent conducting and reflective metal electrodes creates an electrostatic force that unrolls the curled film, closing the artificial eyelid. Fabricated devices have been completed on glass substrates with indium tin oxide electrodes. The curled films have diameters of less than 100 /spl mu/m with the arrays having fill factor transparencies of over 80%.

High-contrast artificial eyelid for protection of optical sensors

The fabrication, testing and performance of a new device for the protection of optical sensors will be described. The device consists of a transparent substrate, a transparent conducting electrode, insulating polymers, and a reflective top electrode layer. Using standard integrated circuit fabrication techniques, arrays of apertures can be created with sizes ranging from micrometers to millimeters. A stress gradient resulting from different thermal coefficients of expansion between the top polymer layer and the reflective metal electrode, rolls back the composite thin film structure from the aperture area once a release layer is chemically etched away, forming a tightly curled film at one side of the aperture - the open condition. The application of a voltage between the transparent conducting and reflective metal electrodes creates an electrostatic force which unrolls the curled film, closing the artificial eyelid. Fabricated devices have been completed on glass substrates with indium tin oxide electrodes. The curled films have diameters of less than 100micrometers with the arrays having mechanical transparencies of over 80%. Greater transparencies are possible with optimized designs. The electrical and optical results from the testing of the artificial eyelid will be discussed including the optimization of the design and fabrication for applications in systems that extend into the IR spectrum. A primary area of investigation is the choice of the transparent conducting electrode.

Electrostatic flexible film actuators as IR choppers for pyroelectric detectors or microbolometers

Flexible film electrostatic MEMS actuators can be used as micromachined IR choppers for pyroelectric and microbolometer sensors. The flexible actuators act as tightly curled shutters, providing transmission of IR radiation to the sensor elements when open and reflection of the IR when closed. These actuators consist of a polymer/metal film stack which is microfabricated and released from a substrate. Thermal and mechanical stress in the film stack causes the actuator to curl when released, and the film can be uncurled by applying an electric field between the curled film and the substrate. Tightly curled actuators in the range of 50 μm to 1 mm square have been fabricated, and arrays have been produced and operated. Operating voltage is in the range of 50 - 300 V with frequencies > 5 kHz. The performance of these actuators is presented, and their applicability to IR choppers is discussed.