This work provides a method of mechanical alignment of an array of single mode fibers to an array of optical devices. The technique uses a micromachined metal spring, which captures a vertical, pre-positioned fiber, moves it into accurate alignment, and holds it for attachment. The spring is fabricated from electroplated nickel, using photodefined polyimide as a plating mask. The nickel is plated about 80 micrometers thick, so that a large fiber depth is captured. In one application, the nickel springs can be aligned to optics on the back side of the substrate. This entire concept is referred to as CLASP (Capture and Locking Alignment Spring Positioner). These springs can be used for general alignment and capture of any fiber to any optical input or output device. Passive alignment of fiber arrays to +/- 2 micrometers accuracy has been demonstrated, with a clear path to improved accuracy.

Light can interact with a material and change the physical dimensions of the material through several mechanisms: photothermal, electrostriction, molecular reorientation, electronic cloud deformation and Cis-Trans isomerization. In the photothermal mechanism light, upon entering a material, is partially absorbed causing a temperature increase and through thermal expansion an increase in size. Electrostriction causes a net force in the material toward regions of higher light intensity which in a pliable material can result in a dimensional change. Molecular reorientation causes anisotropic molecules in a material to experience an alignment force which can lead to a dimensional change. Electronic cloud deformation can result in a dimensional change due to change in nucleon positions due to changes in the materials electronic structure that results from the light's electric field in the material. Molecules that can undergo a Cis-Trans isomerization in the presence of light have the potential to change the shape of any object because of the forces applied to the material. In this paper we will discuss one method by which the photothermal photomechanical effect can be utilized for device fabrication. The basic device, which we call a Mesoscopic Photomechanical Unit (MPU), can be utilized as a positioner/actuator, sensor, and all-optical logic unit.

We detail a new monolithically integrated silicon mold/surface-micromachining process which makes possible the fabrication of stiff, high-aspect-ratio micromachined structures integrated with finely detailed, compliant structures. An important example, which we use here as our process demonstration vehicle, is that of an accelerometer with a large proof mass and compliant suspension. The proof mass is formed by etching a mold into the silicon substrate, lining the mold with oxide, filling it with mechanical polysilicon, and then planarizing back to the level of the substrate. The resulting molded structure is recessed into the substrate, forming a planar surface ideal for subsequent processing. We then add surface-micromachined springs and sense contacts. The principal advantage of this new monolithically integrated mold/surface-micromachining process is that it decouples the design of the different sections of the device: in the case of a sensitive accelerometer, it allows us to optimize independently the proof mass, which needs to be as large, stiff, and heavy as possible, and the suspension, which needs to be as delicate and compliant as possible. The fact that the high-aspect-ratio section of the device is embedded in the substrate enables the monolithic integration of high- aspect-ratio parts with surface-micromachined mechanical parts, and, in the future, also electronics. We anticipate that such an integrated mold/surface micromachining/electronics process will offer versatile high-aspect-ratio micromachined structures that can be batch- fabricated and monolithically integrated into complex microelectromechanical systems.

Texas Instruments has been developing both digital and analog micromirror devices since the late 1970s. The analog flexure-beam micromirror devices are primarily targeted for imaging identification. Digital multiplexing mechanisms are used in column and row selection to address discretized analog signals into the array. Amplifiers and sample-and-hold circuits provide the appropriate signal range to control the micromirrors. Analog-to-digital and digital- to-analog conversions are currently built into the interface electronics, and will potentially be built into the chip. The micromirror devices are built on the top of the addressing circuits using sacrificial layers and two different metal layers. This concept of surface micromachining and mixed-signal circuit integration enables us to investigate the possibility of smart micromachining. Micromirror device applications can expand beyond optical applications into microsensor and other microactuator areas. The addressing circuits can be used in the interface of analog real-world and smart control circuits.

Using a tungsten micro-probe with a tip of 2 micrometers radius, fine metallic powder particles could be manipulated one by one. By applying low voltage (about 10 V) between the probe and a metallic substrate, the powder particle on the substrate was adsorbed to the tip of probe easily, and by cutting off the voltage the powder particle was desorbed from the tip. Therefore it is possible to arrange powder particles as designed by controlling the voltage and movement of the probe. In addition to the powder particle manipulation, powder particles welding was studied. The tungsten micro-probe was contacted with the powder particle on the metallic substrate, and high voltage (about 10 kV) was applied between the probe and the substrate. It was observed that the glow discharge was caused between the powder particle and the substrate. The contacting parts of the powder particle and the substrate were melted and welded each other. By the manipulation and the welding, micro-structures composed of fine powder particles (about 60 micrometers ) were constructed. Powder particle towers and a micro- actuator were fabricated by way of trial. The results demonstrated the potential of the micro- probe assembly for the fabrication of electronic devices, micromachines and intelligent materials.

Recently there has been considerable interest toward designing `smart skin spiral antenna' for aircraft. These antennas when used for EW systems generally require multioctave frequency bandwidths to receive and/or transmit signals over a wide frequency range. In this paper a smart skin conformal antenna is designed which consists of a thin tunable dielectric sheet, interdigital transducer and notch filter and a chiral absorber.

The Structures Division of the Air Force's Wright Laboratory is sponsoring the development and demonstration of a new high pay-off technology termed CLAS--Conformal Load Bearing Antenna Structures. Northrop Grumman Corporation and TRW/ASD are developing the technology under the `Smart-Skin Structure Technology Demonstration (S³D)' program, contract, No. F33615-93-C-3200. The program goal is to design, develop, fabricate, and test a CLAS component and lay the foundation for future work where potential benefits from structurally integrated antennas may be realized. Key issues will focus but are not limited to the design, structures, and manufacturing aspects of antenna embedment into load bearing aircraft structures. Results from Phase I of the program have been previously reported, where initial pay-offs in reducing overall airframe acquisition and support cost, weight, signature, and drag were quantitatively and qualitatively identified. A full-sized CLAS component, featuring a broadband multi-arm spiral embedded in sandwich stiffened structure, will be fabricated and tested for static strength, durability, and damage tolerance. Basic electrical performance, (e.g. radiation patterns, gain, and impedance) will also be verified; however, extensive electrical validation will be the subject of further work. Key aspects of the work and progress to date are detailed below.

The integration of thin film electronics and opto-electronics with MEMs is discussed. Thin film electronics and opto-electronics based on amorphous silicon or polycrystalline silicon are considered for integration with MEMs devices based on piezoelectric thin films or on amorphous or poly-Si thin films.

The integration of optical components with polysilicon surface micromechanical actuation mechanisms shows significant promise for signal switching, fiber alignment, and optical sensing applications. Monolithically integrating the manufacturing process for waveguide structures with the processing of polysilicon actuators allows actuated waveguides to take advantage of the economy of silicon manufacturing. The optical and stress properties of the oxides and nitrides considered for the waveguide design along with design, fabrication, and testing details for the polysilicon actuators are presented.

An eight-mask integrated process for smart microstructures is presented, based on an enhancement-depletion NMOS circuit process and a two-layer polysilicon surface micromachining process. Design and fabrication issues, such as circuit encapsulation, interconnect, and thermal budget are addressed. Two types of micromechanical structures, microcantilever beams and shear stress sensors, were fabricated with on-chip signal conditioning circuits. Electrical test results on circuitry both integrated and not integrated with micromechanisms are discussed. Electromechanical test data demonstrating the resonant frequency of integrated microcantilever beam structures is presented as well as calibrated flow channel data for micromachined shear stress sensors.

In this paper, the integration of interdigital transducers, MEMS and smart electronics is presented with examples including systems for (1) noise suppression in buildings, aircraft cabin, etc. using `smart wall paper', (2) drag sensing and reduction in aircraft, (3) early warning from collapsing bridges, overhead highways, etc., due to earthquakes, flooding, etc., to the approaching vehicles and automatically stopping the vehicles before the damage location, (4) automatic impedance matching for cellular phone communication thus avoiding any interference from other unwanted signals, magnetic fields from the power lines, etc., (5) diesel fuel pollution sensing and control, (6) drip irrigation and (7) deflection and strain measurement of flex beam structure in helicopters. A theoretical analysis and an experiment relating to the later is presented in detail.

Fiber optic embedded sensors can form effective nervous system for smart structures. Several types of fiber optic sensors exist today, of them the Fiber Bragg Grating sensors possess some interesting features. Some of these features are wavelength multiplexing, localized and cumulative sensing. But, the lack of a fast, rugged and inexpensive way to measure the Bragg wavelength has impeded their progress into smart structure applications. In this paper we will analyze a different approach in interrogating such sensors. This approach uses an AM modulated Acousto-Optic Tunable Filter as a fast spectrum analyzer.

In order to create true Smart MEMS systems, the integration of electronics with the MEMS devices is essential. There are currently three methods of integration available: monolithic integration, flip chip attachment and hybrid assembly. The use of flip chip attachment for Smart MEMS has previously been described, and is now available as part of the ARPA- supported MEMS infrastructure programs MUMPs and TechNet. This paper will describe the electromechanical control system chip and the method of using it in conjunction with MUMPs to develop Smart MEMS prototypes.

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.

Automotive passive restraint systems continue to take advantage of the benefits of microelectronics to provide more sophisticated occupant safety features. Traditional microelectronic advantages such as miniaturization, system integration, and part count reduction are being used to a greater level. This paper describes a `smart' automotive accelerometer that performs, in a single integrated component, all of the sensing and signal processing functions required to assess vehicle crash severity and generate a timely airbag deployment command if needed. The device improves system performance and reliability while lowering cost, by replacing the several acceleration-sensitive mechanical switches (and the associated wiring) currently used in most automotive passive restraint systems. The accelerometer consists of a capacitive sense element and a CMOS ASIC which contains interface circuitry and a digital deployment decision circuit. Signal filtering, calibration, and vehicle-specific programming are also performed on-chip. The design approach minimizes the effects of temperature and voltage variations and therefore eliminates the need for separate compensation circuits. Performance of the device in the laboratory as well as in vehicle crash tests demonstrates the accelerometer's ability to meet its design objectives.

The next generation of navigation sensors, which includes microaccelerometers and microgyroscopes, presents high challenges in developing sensitive interface circuits. The shrinking sensor dimensions lead to small output signals that must be processed by the interface electronics. This paper presents a novel interface circuit that can be applied to both fully-differential capacitive and piezoresistive sensors. An equivalent Blumlein Bridge circuit is implemented on CMOS using a novel feedback loop that balances the signals applied to the transducer electrodes. Charge injection is drastically reduced by a double sampling method and a novel adaptive feedback loop that incorporates a compensation switch. The charge injection is reduced to a level below the thermal noise of the opamp. In addition, the feedback loop that is used for reducing the charge injection eliminates supply drift errors. Resolution and stability levels of 10^-8 with a supply variation of 10% are achieved.

In this paper, polymeric 3D MEMS fabricated from UV curable conductive polymer by stereo lithography and ceramic 3D MEMS fabricated by CVD processes are presented. Particular attention is given to the fabrication of micro coil springs of moderate and high aspect ratios. Applications of such devices include drag control in aircraft, beam focusing and steering and electromagnetic shielding and absorption.

We report on measurements of combustion-relevant fuel properties for on-line, feedforward control with small, rugged and fully compensated microsensor-based systems. Such silicon microstructure sensor systems have been demonstrated to determine gaseous and liquid fuel properties such as stoichiometric oxygen demand, octane number, heating value, density and other properties of interest. The measurement approach consists of a three-step process: (1) Measurement of changes in electrical quantities when the sensing elements come in contact with the fluid, (2) Conversion of these quantities into primary sensor outputs, y_i, such as thermal conductivity, specific heat, temperature and pressure, and (3) Correlation between these and the properties of interest, Y(y_i). By coupling this property sensor to an equally rugged and small thermal flow microsensor, millisecond-range response time signals of mass or volume flow, or stoichiometric oxygen demand rate are provided for feed-forward control, without exposing any sensor to harsh exhaust gas environments. Having presented results with gaseous fuels elsewhere, we update these here but concentrate on the determination of octane and cetane number of liquid fuels. Analysis results show that the correlations between these combustion performance properties and physical fuel properties are as good as the ones between octane and critical compression ratio or between cetane and ignition delay. However, all those correlations appear to be limited presently by the accuracy or at least consistency of available data, which are needed for calibration of the sensor system. In checking the temperature dependence of one of the correlations for octane, we found the system output to shift by 15% when using hexadecane as a reference fuel, but only by 1% with iso-octane as reference, for a 10 degree(s)C shift in temperature.

This paper will describe the characterization study conducted to determine the suitability of Flip Chip integration of electronics with MEMS. Successful demonstration of the operation of various MEMS devices in conjunction with Flip Chip is reported. Flip chip solder bumping of integrated circuits is routinely used for packaging purposes and has now been extended to the placement of electronics in close proximity to MEMS devices. The flip chip approach separates the fabrication of the MEMS and electronic devices, allowing both the IC's and MEMS to be fabricated of many different substrate materials, not just single crystal silicon. The close proximity of the electronics to the MEMS devices is very desirable to improve signal to noise performance, and provide higher levels of systems integration. This new approach provides batch fabrication capability as opposed to the serial hybrid approach, without having to fabricate the electronics and MEMS on the same chip. Results on the characterization study of attachment of surface and bulk micromachined structures to glass and silicon substrates is reported.

Recent studies have shown that reflector surface adaptation can achieve performance characteristics on the order of phase array antennas without the complexity and cost. The work proposed in this study develops a class of antennas capable of variable directivity (beam steering) and power density (beam shaping). The actuation for these antennas is employed by either polyvinylidene fluoride film bonded to a metalized mylar skin or shape memory alloys embedded in a composite structure. Theoretical studies of flexible antennas have shown that cylindrical antennas can achieve a directivity variation (beam scanning) of over 10 degree(s) and an increase in ground coverage of over 40%. In this study, prototypes are modeled and simulated to verify results.

Understanding the frictional properties of advanced Micro-Electro-Mechanical Systems (MEMS) is essential in order to develop optimized designs and fabrication processes, as well as to qualify devices for commercial applications. We develop and demonstrate a method to experimentally measure the forces associated with sliding friction of devices rotating on a hub. The method is demonstrated on the rotating output gear of the microengine recently developed at Sandia National Laboratories. In-situ measurements of an engine running at 18300 rpm give a coefficient of friction of 0.5 for radial (normal) forces less than 4 (mu) N. For larger forces the effective coefficient of friction abruptly increases, suggesting a fundamental change in the basic nature of the interaction between the gear and hub. The experimental approach we have developed to measure the frictional forces associated with the microengine is generically applicable to other MEMS devices.

A particle assembly using the electron beam was proposed as a process for creation of multi- functional and intelligent materials. Silica (SiO₂) particles of 5.1 micrometers in diameter were arranged along the prescribed pattern on calcium titanate (CaTiO₃) substrates as the first step on the particle assemblage. Latent electrified images were drawn on CaTiO₃ substrates by scanning electron beam. The substrates were dipped in a suspension of SiO₂ (dipping method) or the suspension was dripped on the higher end of the inclined substrates (dripping method). The SiO₂ particles in the suspension were adhered on the latent image by electrostatic force. And the latent image was visualized as a image of particles arrangement. The images of particles arrangement were processed by an image analysis software. It was shown that the adhered particles can be represented by the normal distribution for the transversal direction to the electrified line, and the uniform distribution for the longitudinal direction. The sharpness of the images by particles was appraised by the above distribution model. It became quantitatively clear that the better images were obtained by the dipping method than by the dripping method.

Tunable electromagnetic wave absorbers for the microwave range comprise polymer-liquid composites, made up of structures of definite shape from low dielectric constant polymer dielectric, filled with polar liquids. Tuning of reflection coefficient is performed in several ways: filling or removal of liquid from the structure, changing composition or temperature of liquid, etc. Effective absorption of electromagnetic waves by these structures in a wide range of frequencies is realized in case frequency dependence of dielectric constant of the liquid is such that for the whole range the condition of resonance absorption is fulfilled. The advantages of polar liquid dielectrics as absorbing media are demonstrated. Absorbing properties of structures with polar liquids and solutions of different salts are compared. Reflection coefficients for several structures of `dielectric on metal' type were measured.

It was demonstrated that the synthesis of polymer complexes (PHAE-Al) occurs between poly(hydroxyamino esters) (PHAEs) and aluminum by using conventional vacuum deposition method in the process of thin metal layer formation on the surface of the polymer. These complexes exhibit electroluminescence similar in spectral characteristics to the well-known low-molecular tris(8-quinolinolato)aluminum complex (Alq₃). Spectral and electrical data for the polymer light-emitting diodes Al/PHAE-Al/PHAE/PANI with PHAEs of various chemical structure are reported.

Active sound transmission control using MEMS sensor and actuator on a thin plate is investigated experimentally. The plate made of aluminum covers the opening of an acoustic enclosure where a sound source is located. The outside acoustic field is measured by a microphone array, which scans a hemispherical surface. The isolation performance of the original plate is poor at its resonance frequencies. The sound transmission through the plate is actively controlled at the resonance frequencies. A one-sensor one-actuator control system minimizes the sensor output by applying a proper electric voltage to the actuator. Global sound reductions of 15 - 22 dB are achieved at the first three resonance frequencies by using same sensor and actuator.

Organic polymer photoconductors are considered as a perspective materials for optically addressed spatial light modulators. A few type of materials were tested. Approach to the choice of materials is suggested.

A novel light-sensitive material has been developed to realize the reversible (as in usual photochromic materials) and irreversible (as in photographic systems) recording of information. The substituted indolinospirobenzopyran was used as a light-sensitive component in polystyrene matrix. At the low exposures in the UV range of spectrum the light-sensitive material works as an usual photochromic one, at large exposure it functions as a photographic layer and in the latter case the irreversible image is registered. The image can be devisualized by heating of the exposed material and restored many times by the flood UV irradiation of the material. The kinetic scheme of photoreaction proceeding in the material is discussed. Besides, in this work new recording materials and process of photochemical image registration were elaborated. Entirely hidden image recorded on this material is visualized in polarized light. The image is stable to the temperature, chemical, mechanical influences. The process is a method of protecting documents, financial securities and products from forgery by incorporation of a `label authenticity' onto the product to be protected. The label of authenticity is obtained by exposing the light-sensitive polymer layer to UV radiation, as a result of which its optical properties change.

The paper investigates absorption of electromagnetic waves by radio engineering structures, filled with liquid dielectrics, in which characteristic size of heterogeneities is much less compared to the wavelength. These structures can be treated as composite materials, possessing effective dielectric constant. Their electrodynamic properties can be computed using equations, derived for composites. An approximate computation method is offered, allowing to compute electrodynamic properties of the structure in analytical form, using equations for the effective dielectric constant of laminated composites. Computed dependencies of electrodynamic properties as a function of structure geometry and dielectric properties of liquids are presented in explicit form, making it easier for analysis, compared to numerical results, obtained by rigorous electrodynamic methods. For a wide range of structures effective dielectric constants and reflection coefficients for the case `absorbing structure on metal' have been computed. A good agreement of computed and experimental results has been observed.

The first experimental observation of the acoustically induced d.c. magnetization (acousto- magnetic effect (AME)) is reported for intense surface acoustic waves (SAW) in a layered structure LiNbO₃ - FeMoP. An amorphous magnetostrictive film exhibited a strong magnetoacoustic (MA) nonlinear behavior under the MA-resonance (MAR) conditions at extremely low magnetic field 30 Oe for 30- MHz MASAW. Transversal AME observed in the experiment was found to be even on MASAW propagation direction and odd in respect to a bias magnetic field orientation. A feasibility of AME applications for a high-sensitive scanning magnetic field sensor was demonstrated.

Passive, nonreciprocal, and optically controlled devices based on dielectric, ferrite, and semiconductor waveguides with metal substrate for the frequency ranges 26 - 48, 80 - 120, and 115 - 145 GHz have been designed and investigated. These devices have better parameters than similar functional elements that use other types of transmission lines. The advantages of the reported devices are as follows: broad band, simple construction, small dimensions, and low weight and price cost. These devices are of interest for dielectric integrated circuits, radars, and communication systems.