A CMOS digital interface chip has been designed and implemented in standard 1.5 μm n-well CMOS technology for detection of current and capacitance variations across a sensing element. An on-chip digitally variable sensor element simulating current and capacitance is monolithically integrated with the readout circuitry. The chip gives an 8-bit digital output and can detect a minimum current and capacitance up to 150 μA and 2.5 fF, respectively.

A CMOS analog multiplexer circuit has been designed for operation at 0.8 V. The circuit consists of transmission gates as switches and an inverter. MOSFETs in the design of multiplexer use the dynamic body bias method. The forward body bias is limited to no more than 0.4 V to avoid CMOS latch-up. The reverse body bias is limited to 0.4 V and allows the MOSFET to turn-off fully and suppresses the sub-threshold leakage. The improved dynamic threshold MOSFET (DTMOS) inverter is engaged to achieve low voltage operation. The CMOS multiplexer chip was designed in standard 1.5 μm n-well CMOS technology and simulated using SPICE. Excellent agreement was obtained between the simulated output waveform and corresponding experimentally measured behavior. The power dissipation is close to 70 nW and signal-to-leakage ratio is 120 dB. The proposed low voltage, ultra-low power analog multiplexer would find application for on-chip neural microprobes and other applications.

A microprobe array for recording neural signals has been designed and fabricated for future monolithic integration with an ultra-low power CMOS operational amplifier circuit on a 2 mm × 2 mm chip. A LIGA-like process is employed utilizing UV lithography and electrodeposition techniques. Probes are fabricated on silicon substrate. The fabrication process is compatible with monolithic integration with CMOS signal processing circuitry. The probes are 210 um high and have an aspect ratio 3:1. Comments are made on processing issues related to chip-level monolithic integration.

The concept of microwave driven smart material actuators is envisioned as the best option to alleviate the complexity associated with hard wired control circuitry for applications such as membrane actuators, insect-like flying objects, or micro-aero-vehicles. Accordingly, rectenna technology was adopted to convert power from microwave to DC and run actuator devices. Previous experimental results showed that 230 VDC output was obtained from a 6 x 6 rectenna array at a far-field exposure (1.8 meters away) with an x-band input power of 20 watts. This result showed the feasibility of using microwaves to power feed and control smart actuators. We have tested a 6 x 6 JPL array patch rectenna which was designed to generate theoretical voltages up to 540 volts. The test result indicated that the performance degradation of Shottky barrier diodes on the rectenna array caused the output voltage to drop. Thus, an estimation of output voltage was made to show the performance beyond the previous measurement by extrapolating and correlating the measured data with a 200 W TWT amplifier in a reverse process. The estimated peak output voltage was 515 volts. In this experiment, due to the degradation of the rectenna performance, we had to measure the output performance based on comparison of the previous result of the rectenna output of a 20W amplifier with the output from the 200 W amplifier. For the real applications, the degradation of Schottky diodes will be a critical issue to be resolved in the fabrication process.

A ferroelectric thin film RF phase shifter on silicon has been designed and developed with the implementation of polysilicon and BST thin film layers on small device area (8 mm²) and fabrication processes fully compatible with current silicon IC technology. The design of a bilateral interdigital coplanar waveguide (BI-CPW) phase shifter is analyzed. This new design has shown a phase shift of 180° at 25 GHz with efficient use of a (Ba,Sr)TiO₃ thin film in the bilateral interdigital finger section. Inherent insertion loss and DC current leakage caused by conductivity of silicon substrate have been investigated. Due to the implementation of polysilicon thin film on silicon, insertion loss was controlled below 6.7 dB and signal dissipation with bias increase was not observed. It is shown that the polysilicon trap layer helped to reduce surface charge accumulation on the silicon surface.

Micromachined antennas have been fabricated on GaAs substrates with the thickness of 100 μm. The patch size of a half-wavelength rectangular-shaped antenna has been reduced about 63.8% by fabricating a folded slot antenna with shorting pins. A quarter-wavelength rectangular shaped antenna and the folded slot antenna on COB show the bandwidth of 300 MHz and 350 MHz, respectively and the quarter wavelength antenna on a MLF package presents the bandwidth of 400 MHz. The bandwidth and antenna gain of the half-wavelength antenna, the quarter- wavelength rectangular shaped antenna, and the folded slot antenna have been measured on COB. For the MLF package, the quarter- wavelength rectangular shaped antenna has only been studied

Planar phased array antenna system on a silicon substrate have been developed, which is an indispensable component for wireless applications. The antenna networks designed for 15GHz applications consists of four patches, four ferroelectric phase shifters, three Wilkinson power dividers, and coplanar waveguide(CPW). The microstrip patch dimension was determined with the aid of simulation tools to have a S11 value of less than 15dB at 15GHz. The Wilkinson power dividers comprised of asymmetrical coplanar strips(ACPS) show a 3dB power splitting, and the phase shifters utilizing the tunability of ferroelectric films generate a linear phase change at the device terminal depending on biased voltages. By controlling the voltages independently applied to each phase shifters, the beam shape and direction radiated from the patches can be changed and steered.

Most wireless sensor networks base their design on an ad hoc (multi-hop) network technology that focus on organizing and maintaining a network formed by a group of moving objects with a communication device in an area with no fixed base stations or access points. Although ad hoc network technologies are capable of constructing a sensor network, the design and implementation of sensor networks for monitoring stationary nodes such as construction sites and nature-disaster-prone areas can be furthered simplified to reduce power consumption and overhead. Based on the nature of immobile nodes, a hierarchical sensor network architecture and its associated communication protocols are proposed in this paper. In this proposed architecture, most elements in the sensor network are designed to be equipped with no functions for message forwarding or channel scheduling. The local control center uses a centralized communication protocol to communicate with each sensor node. The local control center can also use ad hoc network technology to relay the data between each of the sensors. This approach not only minimizes the complexity of the sensor nodes implemented but also significantly reduces the cost, size and power consumption of each sensor node. In addition, the benefit of using ad-hoc network technology is that the local controller retains its routing capabilities. Therefore, power efficiency and communication reliability can be both achieved and maximized by this type of hierarchical sensor network.

This paper presents the design, fabrication and testing of capacitive RF MEMS switches for microwave/mm- wave applications on high-resistivity silicon substrate or glass. The feasibility study and demonstrator fabrication of a new concept of reflector network using MEMS switch based phase-shifters concept for space antennas is presented. These switches can be accurately modeled using 3-D static solvers. The loss in the up-state position is equivalent to the CPW line loss and is 0.1-0.3 dB at 10-40 GHz. It is seen that the capacitance, inductance and series resistance can be accurately extracted from DC-40 GHz S-parameter measurements. The reflector array antennas utilization for phase control avoids the use of very expensive directive antennas and covers a very large frequencies range. We will deal with the configuration, the composition and arrangement of MEMS switches, used to control the phase shift of the electromagnetic wave reflected by each elementary cell.

An innovative holographic imaging technique is applied in characterization of MEMS switch non-linear dynamics. The Duffing's non-linear oscillator based phenomenological model was adopted to study MEMS switch non-linear response due to the complicated contact phenomena and corresponding boundary conditions. An experimental contact measurement result of MEMS cantilever response that matches theoretical trends is provided. Non-destructive contact measurements were performed by means of quantitative nanomechnical test instruments. Non-contact holographic characterization method yielded results comparable with phenomenological model and contact measurements. The proposed holographic characterization method consists of digitized holographic measurements enhanced by the FEM eigenvector problem solution. Two cases were analyzed for simple and perturbated sinusoidal excitations that correspond to the free and contact boundary conditions, respectively.

High performance of RF MEMS phase shifters using polymer bridges and ferroelectric thin film has been demonstrated in this research. To reduce the operating voltage for the RF MEMS phase shifters, polymer bridges and ferroelectric thin film have been implemented. The phase shifter fabricated on a quartz substrate is capable of continuous change in phase up to about 90o (at 15 GHz) with a maximum actuation voltage of 20V. Using polymer as the bridge materials contributes to the reduction in actuation voltage due to their low Young's modulus.

Micro-fabricated RF-MEMS shunt switches on microwave printed circuit boards (PCB) with high dielectric materials are presented. The copper oxide is used as the switch's dielectric layer. The use of copper oxide has a couple of advantages. Firstly, the high dielectric constant of copper oxide (ε_r≈18.1) provides higher down state capacitance, which can re-position the isolation valley at the lower frequency band. Secondly, the fabrication steps to grow copper oxide layer becomes relatively straightforward as opposed to the deposition of silicon nitride. To improve the switching performance by achieving a desirable high capacitance ratio, the down state capacitance must be as high as possible. The down state capacitance and capacitance ratio of copper oxide is found to be higher than with silicon nitride for the same size of overlapping area, between membrane and bottom electrode. A switch with copper oxide is shown to have a lower isolation valley frequency as opposed to that with a silicon nitride layer.

This paper presents the design and development of a gas sensor based on phase monitoring of reflected waves at radio frequencies for various dichloromethane vapors. Composite thin film with functionalized carbon nanotubes (f-CNT) and polymethylmethacrylate (PMMA) was employed as a sensing material on a coplanar waveguide and its impedance was monitored for various concentrations. Conductivity change of the composite due to absorption of dichloromethane vapors was clearly observed by resistance measurements. When the f-CNTs/PMMA composite is exposed to dichloromethane with low vapor concentration, phase monitoring of reflected waves from resistive load exhibited higher sensitivity than resistance measurements. With high sensitivity at radio frequency, a wireless gas sensing network integrated with power divider and antenna is introduced.

Screen-printing processes offer advantages in producing directly patterned and integrated piezoelectric elements, and fill an important technological gap between thin film and bulk ceramics. However, several existing problems in the screen-printed piezoelectric thick films, such as the poor reliability and the required high sintering temperature, are significantly limiting their applications. In this work, lead zirconate titanate (PZT) ceramic films of 30 μm in thickness were deposited on Pt-coated silicon substrates by the screen-printing process, in which the ceramic pastes were prepared through a chemical liquid-phase doping approach. Porous thick films with good adhesion were formed on the substrates at a temperature of 925°C. Stable out-of-plane piezoelectric vibration of the thick films was observed with a laser scanning vibrometer (LSV), and the piezoelectric dilatation magnitude was determined accordingly. Our piezoelectric measurements through the areal displacement detection with LSV exhibited distinct advantages for piezoelectric film characterization, including high reliability, high efficiency, and comprehensive information. The longitudinal piezoelectric coefficients of the thick films were calculated from the measured dilatation data through a numerical simulation. High piezoelectric voltage constants were obtained due to the very low dielectric constant of the porous thick films. The application potentials of our screen-printed thick films as integrated piezoelectric sensors are discussed.

Novel devices can be relatively simple in theory and modeling, but difficult and many times unfeasible to fabricate in a traditional cleanroom environment. We have developed a CAD/CAM tool capable of integrating multiple materials in the electronic, photonic, and biological regimes for applications in both MEMS and BioMEMS devices. Some materials are known and more fully characterized, such as thick film resistors or conductors, while other materials such as biodegradable scaffolding are new but showing promise to realize heterogenous tissue engineered constructs and drug delivery devices. The tool does not discriminate, but rather places these materials in specified locations with precision volumetric control, gently, conformally, and in 3-D. This paper will describe the enabling aspect of true 3-D maskless fabrication as well as describe multiple device structures and demonstrations.

Simulation of piezoelectrically actuated valveless microupump (PVAM) indicates that both the pumping rate and membrane deflection amplitude will increase with the increase of the actuating frequency at a low frequency range (<7.5 kHz). However, because of the electro-mechanical-fluid coupling, the membrane deflects in an undesirable way at high frequencies. This will lower the pumping rate at high frequencies (>7.5 kHz). At even higher frequencies (>50 kHz), the pumping rate will decrease further because the deflection amplitude decreases. This agrees with reported experimental results. The changing membrane deflection shape at various frequencies clearly plays an important role in the performance of the pump.

Nanocrystals and nanostructures will be the building blocks for future materials that will exhibit enhanced or entirely new combinations of properties with tremendous opportunity for novel technologies that can have far-reaching impact on our society. It is, however, realized that a major challenge for the near future is the design, synthesis and integration of nanostructures to develop functional nanosystems. In view of this, this exploratory research seeks to facilitate the development of a controlled and deterministic framework for nanomanufacturing of nanotubes as the most suitable choice among nanostructures for a plethora of potential applications in areas such as nanoelectronic devices, biological probes, fuel cell electrodes, supercapacitors and filed emission devices. Specifically, this paper proposes to control and maintain the most common nanotube growth parameters (i.e., reaction temperature and gas flow rate) through both software and hardware modifications. The influence of such growth parameters in a CVD process on some of the most vital and crucial aspects of nanotubes (e.g., length, diameter, yield, growth rate and structure) can be utilized to arrive at some unique and remarkable properties for the nanotubes. The objective here is, therefore, to control the process parameters to pinpoint accuracy, which would enable us to fabricate nanotubes having the desired properties and thereby maximize their ability to function at its fullest potential. To achieve this and in order to provide for experimental validation of the proposed research program, an experimental test-bed using the nanotube processing test chamber and a mechatronics workstation are being constructed.

Carbon nanotubes with certain shapes and 2D or 3D structures have versatile potential applications. Aligned and coiled carbon nanotubes were synthesized by microwave chemical vapor deposition. Due to its faster heating and cooling processes, microwave chemical vapor deposition can be an economic method for various carbon material fabrications. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were performed to observe the micro- and nano-structure of these materials. Their properties and potential applications were also discussed.

Recent studies at the Rensselaer Polytechnic Institute have shown that electric field can have a profound effect on individual carbon nanotube ensembles. We have shown that nanotubes can be aligned along the electric field lines, and can also be made to move along the field lines above a critical or threshold electric field. Experiments were repeated with nano-particles such as C-60 (fullerenes) and these effects were not observed, which indicates that the aspect ratio and one-dimensionality of the nanotubes plays a critical role. These observations can foreshadow novel electro-mechanical applications for nanotube elements.

The paper discusses the development of polymer composite materials based on carbon nanotubes. Carbon Nanotubes can be used to form polymer hybrid materials that have good elastic properties, piezoresistive sensing, and electrochemical actuation. Of particular interest are smart nanocomposite materials that are strong and self-sensing for structural health monitoring, or self-actuating to improve the performance and efficiency of structures and devices. Since nanoscale research is broad, challenging, and interdepartmental, undergraduate through Ph.D. level students and faculty have combined efforts to attack the special problems related to building nanoscale smart materials. This paper gives an overview of the work being performed to manufacture polymer nanocomposite materials starting from nanotube synthesis through to device fabrication and testing. Synthesis is performed using an EasyTube Nanofurnace, functionalization is done using plasma coating, dispersion using rotary mixing and ultrasonication, and processing using vacuum and pressure casting. Reinforced polymers, a carbon nanotube solid polymer electrolyte actuator, and piezoresistive sensors are being developed for several potential applications. The materials produced indicate that carbon nanotube hybrid smart materials may become a new class of smart material with unique properties and applications, but much work still needs to be done to realize their full potential.

Particles dispersively coated with other material is a kind of composite particles, i.e., core particles are dotted with other material. Two methods have been developed for such the composite particles. One is a forced electrification method and the other a rotating drum method. The former utilizes the electrostatic force, i.e., positively electrified core particles and negatively electrified child particles are mixed. The latter is a mechanical method as follows. Core particles and child particles are charged into a cylindrical vessel, and mixed by rotating the vessel for several hours. We prepared composite particles of PTCR (Positive Temperature Coefficient of Resistivity) barium titanate and the junction metal such as indium and solder. When the composite particles are filled, the junction metal always exists between the neighboring core particles. The PTCR property of the filling is almost the same with that of the sintered barium titanate. We fabricated a PTCR thin sheet by packing the composite particles between two sheet electrodes. If the composite particles are electrically connected but fixed not firmly, the sheet shows PTCR property and can bend by rearrangement of the particles. Thin ceramics sheet is practically impossible because of the brittleness. However, flexibility can be given to the sheet of the PTCR-junction metal composite particles. The composite particles are fixed by enveloping in an evacuated bag or by embedding in a heat resistant resin. Advantages and disadvantages of the preparation methods and fabrication methods are discussed. Preliminary experiments for a new approach to the PTCR sheet are introduced.

New method to fabricate the metallic closed cellular material containing organic materials for the damping systems has been developed. Powder particles of polystyrene coated with a nickel-phosphorus alloy layer using electro-less plating were pressed into pellets and sintered at high temperatures by a furnace and a spark plasma sintering (SPS) system. A metallic closed cellular material containing polystyrene was then fabricated. The physical, mechanical and damping properties of this material were measured. The density of this material is smaller than that of other structural metals. The results of the compressive tests show that this material has the different stress-strain curves among the specimens that have different thickness of the cell walls and the sintering temperatures of the specimens affect the compressive strength of each specimen. Also, it seems that the results of the compressive tests show that this material has high-energy absorption and Young's modulus of this material depends on the thickness of the cell walls. The loss factor of this material was measured and the results show that this material has a large loss factor than that of structural metals. These obtained results emphasize that this metallic closed cellular material can be utilized as energy absorbing material and passive damping material.

Block copolymer-based membrane technology represents a versatile class of nanoscale materials in which biomolecules, such as membrane proteins, can be reconstituted. Our work has demonstrated the fabrication of large-area, protein- enhanced membranes that possess significant performance improvements in protein functionality. Among its many advantages over conventional lipid-based membrane systems, block copolymers can mimic natural cell biomembrane environments in a single chain, enabling large-area membrane fabrication using methods like Langmuir-Blodgett (LB) deposition, or spontaneous protein-functionalized nano-vesicle formation. The membrane protein, Bacteriorhodopsin (BR), found in Halobacterium Halobium, is a light-actuated proton pump that develops gradients towards the demonstration of coupled functionality with other membrane proteins to effect ATP production, or production of electricity through Bacteriorhodopsin activity-dependent reversal of Cytochrome C Oxidase (COX), found in Rhodobacter Sphaeroides. Using quantum dot-labeled, engineered protein constructs, we have demonstrated large-scale insertion of proteins into block copolymer Langmuir-Blodgett (LB) films as well as measurable pH changes based upon light-actuated proton pumping. Light actuated-activity across the protein-functionalized membrane when fully enclosed in a sol-gel matrix has also been observed using impedance spectroscopy. Initial data has suggested a significant pH change of up to 1.75 in a volume of 100 mL and surface area of 0.317cm², a level that is capable of powering a number of proton-gradient dependent proteins towards the buildup of a robust, hybrid protein/polymer device. Recent atomic force microscopy studies of the protein-embedded polymer film samples have revealed the formation of protein aggregate-based pattern generation with very uniform torus-shaped rings. Current work focused towards characterizing the effects that various pattern formations can have on the efficiency of protein functionality, as well as film stability in an effort to develop a robust polymer membrane will also be discussed.

Nanosized tin oxide particles have shown excellent performance when used as anode material in lithium ion batteries. To further improve their electrochemical properties, functionalized carbon nanotubes were introduced during the homogenous precipitation synthesis. Various material characterization techniques such as XRD, SEM, TEM, TGA and BET were performed to check their crystalline, micro- and nano-structure, thermal stability and surface area. Compared with blank tin oxide nanoparticles, much finer tin oxide nanoparticles with higher surface area were observed with the presence of functional carbon nanotubes. It is proposed that functional carbon nanotubes play an important role for nanoparticles' nucleation, growth, coagulation processes. The potential application of this composite in lithium ion batteries is discussed.

Hydrogels are “smart” polymers that respond to an external stimulus with a change in their physical characteristics. The response of gel microstructures, or microgels, to an external stimulus depends on their size and synthesis route. Smart microgels based on poly (N-isopropylacrylamide) and poly (methacrylic acid) were prepared by combining the aspects of x-ray lithography and a novel synchrotron-radiation-induced polymerization. The morphology of microgels prepared by this novel synthesis route was characterized by optical and atomic force microscopy to better understand their response properties. Microgels obtained from this method are in a hydrophobic state and are richly nanoporous in their morphology. Average pore size of these gel networks lies within a few hundreds of nanometers as observed from atomic force microscopy. Due to their ultrafast response, these microgel structures can be used as microtransducers that respond to a change in moisture concentration.

Micro-Opto-Electro-Mechanical (MOEM) accelerometers employing a cantilever beam and anti resonant reflecting optical waveguide (ARROW) on a silicon is analyzed. Two types of MOEM accelerometers and a closed loop operation that can enhance the performance significantly compared to MEMS accelerometer is presented. As a typical example our study shows a MOEM accelerometer with a minimum detectable acceleration of 0.255 μ g/√Hz, a dynamic range of 160g, scale factor stability of 1.57 ppm/°c and shock survivability of more than 1000 g.

In designing microelectromechanical systems (MEMS), the robustness of the system critically affects long-lasting system performance. In reality, fabrication errors, material property uncertainty, and environmental uncertainty such as temperature and humidity variations affect the performance of MEMS. These factors are usually referred to as noise factors. This investigation is mainly concerned with the robust design of micro electro-thermal actuators that are to be fabricated by the MEMS fabrication technology. The baseline design is found by topology optimization method which gives an initial optimal shape of an electro-thermal actuator giving the maximum output for a given input. By the mathematical topology optimization method alone, it is difficult or impossible to consider all noise factors in the final design stage. To take into account noise factors, we will employ the robust design methodology and modify the baseline design obtained by the topology optimization. In this work, robust design will be considered with micro electro-thermal actuators. The electro-thermal actuator is an actuating device using the thermal expansion by Joule’s heat, so its performance is affected by the temperature variation of surrounding air, convection, thermal expansion, and applied voltage among others. We consider these noise factors for the final design to improve its robustness against the noise factors. Several micro electro-thermal actuators were fabricated by the MEMS fabrication technology and a series of experiments were conducted to verify the effect of the robust design concept on the final design.

This paper presents a novel method for surface micro-machining of pin-jointed actuators using only two active polySi layers. An alternative sacrificial layer deposition and etching sequence is proposed in order to achieve the linkage construction. The implementation of a four-level profile in the first sacrificial layer is a key factor to significantly reduce topography issues when depositing subsequent layers. Adding to this are some design considerations to further smooth the surface topography irregularities so that a reasonable clearance between the first and second mechanically active layers is obtained. As a result, the need of a planarization process step is foreseen to be avoided. The main advantages of the proposed construction technology are process simplification and standardization conditions in key deposit steps.

A hybrid system consisting of a resonant piezo layer (RPL) and a resonant SOI micromechanical sensor is conceived in this work as highly sensitive gravimetric sensor for applications in various fields. The idea consists in using PZT screen-printed elements, behaving as thickness-mode resonators, coupled to a micro-mechanical resonator based on a SOI technology. The PZT resonator induces oscillations to the micromechanical device and, if the resonance condition is matched for this latter system, a sensitivity of 5000 Hz/μg can be obtained when a variation of the proof mass occurs. Prototypes of both the mentioned two constitutive parts have been separately realized by the authors showing potentials for batch production. Several different experimental MEMS prototypes, mainly made by a central proof-mass sustained by four compliant beams anchored to its four corners, have been realized. Both Front Side and Back Side DRIE etching procedures have been performed improving the proof mass value with respect to a different set of prototypes realized by using a standard CMOS technology. Even if a low resonance frequency characterize the realized micro-prototypes a drastically improved value of the quality factor allow to obtain very high gravimetric sensitivity then to detect very small changes in the proof mass value due i.e. to chemical or physical compound absorption over the mass surface. Electrical or optical sensing can be adopted, depending on materials embedded into the considered device, as already demonstrated by the authors. Polysilicon strain gauges have been embedded into the springs while optical readout can be addressed by using a novel class of metal-dielectric photonic-band gap materials. In this latter case a process step, which consists of depositing suitable thin films, must be take into account.

A new position sensor based on laterally movable gate FET (LMGFET) sensing element has been designed and fabricated. The position sensor is designed to operate in a differential mode, which increases device sensitivity and performance. The moving proof mass is supported on each end by a folded beam which is also employed as a spring to restrain motion. The simulated value of the folded beam spring constant designed in this work is 44.8 N/m. The LMGFET microstructure is fabricated by a four-mask LIGA-like post-IC process compatible with standard CMOS fabrication technology. p+ region is ion-implanted under the moving structure as a ground plane and also to decrease leakage currents. Plasma ashing is employed to avoid stiction. The design of the sensor along with fabrication steps is described. Preliminary results on the electrical behavior of the fabricated LMGFET are given.

Electroactive polymers (EAPs) are capable of converting energy in the form of electric charge and voltage to mechanical force and movement and vice versa. Several electroactive polymer actuator materials whose responses are controlled by external electric fields, e.g. poly(vinylidene fluoride-trifluoroethylene) based fluoroterpolymers, have generated considerable interest for use in applications such as artificial muscles, sensors, parasitic energy capture, and integrated bio-microelectromechanical systems (BioMEMS) due to their high electric-field induced strain, high elastic modulus, high electromechanical coupling and high frequency operation, etc. The combination of micro-optics and MEMS, referred to as micro-opto-electromechanical systems (MOEMS), makes a new opportunity for innovation in the EAP field. There is a lot of pioneering work on optical beam deflection by electromechanically driven digital micromirrors. In this paper we describe a flexible polymer deformable micromirror (PDM) light-valve technology based on high-performance electroactive polymer materials and microactuators for high-quality electronic projection display and imaging systems. The excellent electromechanical properties of these electroactive polymer microactuators greatly improve the electro-optical properties of the deformable micromirrors and light valves, e.g., optical switching behavior, deformation amplitude and contrast, and low-voltage and high-frequency operation. The material selection, device fabrication, characterization, and a theoretical analysis using the finite element analysis code will be investigated. This technology is compatible with CMOS technology for an active matrix addressing on a chip. High-resolution phase-modulating polymer light valves may permit a lot of future applications, and electroactive polymer micromachining lends flexibility to displays application.

This paper discusses the prospects of light-driven actuation particularly for actuating fluids at micro-scale for potential use in a novel retinal prosthesis and other drug delivery applications. The prosthesis is conceived to be comprised of an array of light-driven microfluidic-dispenser units, devices that eject very small amounts of fluids on the order of 1 picoliter per second in response to incident light energy in the range of 0.1-1 mW/cm². A light-driven actuator, whose size will ideally be smaller than about 100 micrometers in diameter, independently powers each dispenser unit. Towards this application, various approaches for transducing light energy for actuation of fluids are explored. These approaches encompass both direct transduction of light energy to mechanical actuation of fluid and indirect transduction through an intermediary form of energy, for instance, light energy to thermal or electrical energy followed by mechanical actuation of fluid. Various existing schemes for such transduction are reviewed comprehensively and discussed from the standpoint of the application requirements. Direct transduction schemes exploiting recent developments in optically sensitive materials that exhibit direct strain upon illumination, particularly the photostrictive PLZT (Lanthanum modified Lead Zirconate Titanate), are studied for the current application, and results of some preliminary experiments involving measurement of photovoltage, photocurrent, and photo-induced strain in the meso-scale samples of the PLZT material are presented.

This work describes online programmable microfluidic bioprocessing units using digital logic microelectrodes for rapid pipelined translocation of DNA molecules and other charged biopolymers as well as nanoparticles. Fundamentals of the design and fabrication technique both the silicon-PDMS and a polyimide-PDMS based construction (a new method based on conventional printed circuit board materials) of these electronic microfluidic devices and their functions are described as well as the experimental results along with the first proof of principle functionality. The electronically controlled collection, separation and channel transfer of the biomolecules and nanosized beads are monitored by a sen-sitive fluorescence setup and controlled by a custom-designed hardware for camera-control and feature selection. This hybrid reconfigurable architecture couples electronic and biomolecular information processing via a single module combination of fluidics and electronics and opens new fields of applications not only in DNA computing and molecular diagnostics but also in applications of combinatorial chemistry and lab-on-a-chip biotechnology to the drug discovery process.

There is an urgent need for real-time bio-detectors with high performance, such as high sensitivity, small size, easy deployment. Sensor platforms based on MEMS, such as microcantilevers (including piezoelectric and silicon-based cantilevers), have been studied. Piezoelectric-based micro-diaphragm, micro-electromechanical diaphragm (MEMD), used as micro-sensor platform, is reported in this article. It is found that the sensitivity of the sensor based on micro-diaphragm is much higher than that based on the micro-cantilever. Since a lower density of material used in the diaphragm results in a better sensitivity, PVDF-based piezoelectric polymer was chosen to fabricate the devices. Both cantilevers and diaphragms made of the same piezoelectric polymer were characterized in order to compare the difference of quality merit factor (Q-value) between the cantilever and diaphragm. It is experimentally found that the Q-value of the diaphragm is higher than that of the cantilever. More importantly, the damping effect of liquid media on diaphragm is much smaller than that that on cantilever. All these indicate that as a sensor platform the micro-diaphragm is much better than the micro-cantilever.

The design of a novel feedback sensor system with wireless implantable polymer MEMS sensors for detecting and wirelessly transmitting physiological data that can be used for the diagnosis and treatment of various neurological disorders, such as Parkinson's disease, epilepsy, head injury, stroke, hydrocephalus, changes in pressure, patient movements, and tremors is presented in this paper. The sensor system includes MEMS gyroscopes, accelerometers, and pressure sensors. This feedback sensor system focuses on the development and integration of implantable systems with various wireless sensors for medical applications, particularly for the Parkinson's disease. It is easy to integrate and modify the sensor network feed back system for other neurological disorders mentioned above. The monitoring and control of tremor in Parkinson's disease can be simulated on a skeleton via wireless telemetry system communicating with electroactive polymer actuator, and microsensors attached to the skeleton hand and legs. Upon sensing any abnormal motor activity which represent the characteristic rhythmic motion of a typical Parkinson's (PD) patient, these sensors will generate necessary control pulses which will be transmitted to a hat sensor system on the skeleton head. Tiny inductively coupled antennas attached to the hat sensor system can receive these control pulses, demodulate and deliver it to actuate the parts of the skeleton to control the abnormal motor activity. This feedback sensor system can further monitor and control depending on the amplitude of the abnormal motor activity. This microsystem offers cost effective means of monitoring and controlling of neurological disorders in real PD patients. Also, this network system offers a remote monitoring of the patients conditions without visiting doctors office or hospitals. The data can be monitored using PDA and can be accessed using internet (or cell phone). Cellular phone technology will allow a health care worker to be automatically notified if monitoring indicates an emergency situation. The main advantage of such system is that it can effectively monitor large number of patients at the same time, which helps to compensate the present shortage of health care workers.

Endoscopic optical coherence tomography (EOCT) is a medical imaging technique that uses infrared light delivered via an endoscope to produce high-resolution images of tissue microstructure of the gastrointestinal tract. A key component of an EOCT system is the method used to scan the infrared beam across the tissue surface. We have begun developing electrostatic MEMS micromirror devices for use in EOCT. These devices consist of 1 mm square gold-plated silicon mirrors on polyimide tables that tilt on 3 micron thick torsion hinges. The MEMS actuator used to tilt the mirror, the integrated forces array (IFA) is a thin (2.2 μm) polyimide membrane consisting of hundreds of thousands of deformable capacitors that can produce strains up to 20% and forces equivalent to 13 mg with applied voltages from 30-120 V. Measurements of optical deflections of these devices range from 18° at low frequencies to more than 120° near the resonant frequencies of the structures (30-60 Hz). The support structures, hinges, and actuators are fabricated from polyimide on silicon using photolithography. These electrostatic MEMS micromirrors were inserted into the scanning arm of an OCT imaging system to take in vitro images of porcine tissue and in vivo images of human skin at frame rates from 4-8 Hz. SLA probe tips were designed and fabricated to align the optics of the device and to protect the fragile polyimide devices during endoscopic imaging. In addition, devices are being fabricated that combine the IFA and mirror structures onto a single silicon wafer, reducing fabrication difficulty.

In this paper we report on the characterisation of a smart ASIC chip comprising a pair of room temperature resistive vapour sensors in a ratiometric configuration. This novel design enables the near elimination of several undesirable baseline effects and provides an automatic offset of the output signal. The novel ASIC chip has been designed and fabricated through a standard 0.7 μm CMOS process. The ASIC response has been modelled prior to fabrication as reported elsewhere. There are two main stages in the circuit: one for the processing and conditioning of the sensor signals and the other for temperature control. Two sets of sensor electrodes are positioned in two opposite corners of the chip and are connected in a non-inverting operational amplifier configuration. Carbon black/polymer composite materials have been deposited across the electrodes to create the sensing chemoresistors and illustrate the functionality of the chip. Sample devices were created by depositing either the same nanomaterial on both electrodes and having one active and one passive sensor, or by depositing two different materials, thus creating two active sensors. Following deposition, the responses of the ASIC devices to toluene and ethanol vapours in air have been characterised in an automated mass flow system and presented here.

In this paper, a design approach was proposed to define suitable structures of distributed controlled MEMS used in a pneumatic two-dimensional microconveyance system. After an introduction to distributed systems, a brief survey of their applications in the field of micromanipulation and prospect in industrial microfabrication was presented. Afterward, the authors introduced the notion of intelligent motion surface used in the field of pneumatic microconveyance. They analyzed suitable distributed structures based on elementary microconveyance, which are supposed to provide an appropriate air-flow force and overcome microfluidic problems. The first microconveyer prototype was fabricated by using bulk micromachining technique. It was developed to estimate MEMS density required to produce an elementary force to convey a micro-object. Then, a specific distributed structure was proposed to develop the pneumatic two-dimensional microconveyer device. The device size is 35 x 35 mm² for 560 MEMS-microvalves, controlled by distributed arrays and processed by a centralized intelligence via a microprocessor. From experimental conveyance results, we can conclude to the feasibility of the pneumatic microconveyance by distributed air-flow microactuators.

This paper reports a novel ultra-fast chemosensor array microsystem for the rapid detection of volatile organic compounds (VOCs). The sensing device consists of an array of 80 miniature resistive sensors on a 10 mm by 10 mm silicon substrate, configured in 5 rows of 16 elements. In this application each row has been deposited with a different carbon black/polymer composite nanomaterial. As a result of arranging the sensors in the matrix fashion, we are able to represent the sensor response as an olfactory image. The sensor array was tested with pulses of ethanol, toluene, toluene and ethanol mixture, milk, cream, cypress oil and peppermint oil at two different flow rates (60 and 130 ml/min) and three different pulse widths (10, 25, and 50 secs). Preliminary analysis was performed by comparing different images which showed excellent discrimination between the different analytes. Increasing the pulse width and flow rate improved the discrimination capability of the system. We have also investigated the effect of 'stereo' olfactory imaging by combining mono images measured at different flow rates to form a composite image. Results have shown such scheme can provide additional discriminatory information.

Sensors play a crucial role in structural systems with the concern of reliability/failure issues. The development of wireless monitoring systems has been of great interest because wireless transmission has been proven as a convenient means to transmit signals while minimizing the use of many long wires. However, the wireless transmission systems need sufficient power to function properly. Conventionally, batteries are used as the power sources of the remote sensing systems. However, due to their limited lifetime, replacement of batteries has to be carried out periodically, which is inconvenient. In recent years, piezoelectric materials have been developed as sensing and actuating devices mostly, and power generators in some cases. In this paper, a self-powered piezoelectric sensor is studied, in which one piece of piezoelectric material will be simultaneously used as a sensor and a power generator under vibration environment. Concurrent design with piezoelectric materials in sensor and power generator is integrated with energy storage device. We evaluate sensing and power generating abilities individually, and then their concurrent sensing and energy harvesting performances. The possibilities of the piezoelectric sensor to power wireless transmission systems are discussed. Experimental efforts are carried out to study the feasibility of the self-powered piezoelectric sensor system.

An electroactive polymer (EAP), high energy electron irradiated poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer, based actuation micropump diaphragm (PAMPD) has been developed for air flow control. The displacement strokes and profiles as a function of amplifier and frequency of electric field have been characterized. The volume stroke rates (volume rate) as function of electric field, driving frequency have been theoretically evaluated, too. The PAMPD exhibits high volume rate. It is easily tuned with varying of either amplitude or frequency of the applied electric field. In addition, the performance of the diaphragms were modeled and the agreement between the modeling results and experimental data confirms that the response of the diaphragms follow the design parameters. The results demonstrated that the diaphragm can fit some future aerospace applications to replace the traditional complex mechanical systems, increase the control capability and reduce the weight of the future air dynamic control systems.

We report our advances in nuclear magnetic resonance force microscopy (NMRFM) in three areas: 1) MEMS microfabrication studies of single-crystal-silicon mechanical oscillators using double-sided processing; 2) micromagnetometry, anisotropy, and dissipation studies of individual permalloy micromagnets on oscillators; and 3) mechanical-oscillator detection of NMR in the magnet-on-oscillator scanning mode. In the first area, we report details of our back-etch microfabrication process, and characterize oscillator resonant frequency, quality factor, and spring constant by measuring the noise spectral density of oscillator motion. In the second studies, we report changes in the resonant frequency and quality factor for each of four modes of our oscillators for two shapes and sizes of permalloy thin-film (~30 and 180~nm) micromagnets; a simple, quantitative model is used to describe both low-field softening and high-field stiffening. Finally, we report scanning-mode NMR force detection of an ammonium-sulfate single-crystal interface and a polymethyl-methyl-acrylate thin film at room temperature. These latter studies use 2-μm-radius permalloy magnets on silicon oscillators to image the NMR response from resonant volumes as small as 3 μm³. These NMRFM studies are the first reported that attain sub-micron resonant-slice resolution at room temperature.

This paper describes an analytical approach for the characterization of sputtered thin film microthermocouples (STFMT) to determine the thermophysical properties of microstructures. A complete spatially one-dimensional (1D) boundary value problem with a thin film sputtered sample sandwiched between an heater/RTD (Resistance Temperature Detector) at its one end and the thin film microthermocouple at its other end has been solved to show the effects of various thermoelements on Seebeck voltage, heat loss/gain effects between the device & the environment, as well as at the contact area between the sample and microthermocouple tip. An interesting outcome for three different pairs of thermoelements studied (one material is always Titanium, and the other is Chromium, Chromium-Silicide and Tantalum, in turn) is that higher the Seebeck voltage of the microthermocouples under consideration, less accurate is the temperature sensed by it.

This work deals with the development of integrated relative humidity dew point sensors realized by adopting standard CMOS technology for applications in various fields. The proposed system is composed by a suspended plate that is cooled by exploiting integrated Peltier cells. The cold junctions of the cells have been spread over the plate surface to improve the homogeneity of the temperature distribution over its surface, where cooling will cause the water condensation. The temperature at which water drops occur, named dew point temperature, is a function of the air humidity. Measurement of such dew point temperature and the ambient temperature allows to know the relative humidity. The detection of water drops is achieved by adopting a capacitive sensing strategy realized by interdigited fixed combs, composed by the upper layer of the adopted process. Such a capacitive sensor, together with its conditioning circuit, drives a trigger that stops the cooling of the plate and enables the reading of the dew point temperature. Temperature measurements are achieved by means of suitably integrated thermocouples. The analytical model of the proposed system has been developed and has been used to design a prototype device and to estimate its performances. In such a prototype, the thermoelectric cooler is composed by 56 Peltier cells, made by metal 1/poly 1 junctions. The plate has a square shape with 200 μm side, and it is realized by exploiting the oxide layers. Starting from the ambient temperature a temperature variation of ΔT = 15 K can be reached in 10 ms thus allowing to measure a relative humidity greater than 40%.

A powerful experimental tool, ultra-sharp nano-electrode array is designed, fabricated and characterized. The application on a combination of Scanning Electrochemical Microscopy (SECM) and the Atomic Force Microcopy (AFM) is demonstrated. It can measure sample electrochemically initiated by SECM changes of topography while detecting topography using AFM. In order to realize this, a specialized probe system that is composed of a micro-mechanical bending structure necessary for the AFM mode and an electrochemical UME-tip required for a high performance SECM is crucial. The probe array is a row of silicon transducers embedded in silicon nitride cantilever array. The sharp high-aspect ratio (20:1) silicon tips are shaped and a thin layer of silicon nitride is deposited, which embeds the silicon tips in a silicon nitride layer so that they protrude through the nitride. Thus, the embedded silicon tips with a diameter less than 600 nm, the top radius less than 20 nm, and the aspect ratio as high as 20 can be achieved. A metal layer and an insulator layer are deposited on these tip structures to make each probe selectively conductive. Finally, cantilever structures are shaped and released by etching the silicon substrate from the backside. Electrochemical and impedance spectroscopic characterization show electrochemical functionality of the transducer system.

The concept of a bio-nanobattery is based on ferritin, an iron storage protein that naturally exists in most biological systems. Biomineralization allows ferritins to reconstitute iron core with various metallic cores. When the ferritin half cells are integrated into a complete battery system, the fabrication of well-organized ferritin arrays is necessary and very important to enhance the overall battery performance, improving the battery power density, the power discharge rate, the compactness of battery size, etc. In this work, a spin self-assembly (SA) method was used for producing a thin-film array structure of ferritins. The spin SA deposition was repeated until two bilayers of cationized and native ferritins or 4 alternating ferritin layers were achieved. High-resolution field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and variable angle spectroscopic ellipsometry (VASE) were used to characterize the multilayered ferritin arrays. The thickness of ferritin multilayer increased linearly as the spin SA deposition was repeated. The spin SA deposition method produced well-organized, uniform, and flat ferritin layers in a much shorter period of time, compared with Langmuir-Blodgett or dipping deposition methods. Such enhancement can be attributed to a strong electrostatic attraction that holds the ferritin layer on the substrate during the spin-coating process while hydrodynamic drag and centrifugal forces remove loosely-bound ferritins.

Platinum-cored ferritins were synthesized as electrocatalysts by electrochemical biomineralization of immobilized apoferritin with platinum. The platinum cored ferritin was fabricated by exposing the immobilized apoferritin to platinum ions at a reduction potential. On the platinum-cored ferritin, oxygen is reduced to water with four protons and four electrons generated from the anode. The ferritin acts as a nano-scale template, a biocompatible cage, and a separator between the nanoparticles. This results in a smaller catalyst loading of the electrodes for fuel cells or other electrochemical devices. In addition, the catalytic activity of the ferritin-stabilized platinum nanoparticles is enhanced by the large surface area and particle size phenomena. The work presented herein details the immobilization of ferritin with various surface modifications, the electrochemical biomineralization of ferritin with different inorganic cores, and the fabrication of self-assembled 2-D arrays with thiolated ferritin.

Currently available power storage systems, such as those used to supply power to microelectronic devices, typically consist of a single centralized canister and a series of wires to supply electrical power to where it is needed in a circuit. As the size of electrical circuits and components become smaller, there exists a need for a distributed power system to reduce Joule heating, wiring, and to allow autonomous operation of the various functions performed by the circuit. Our research is being conducted to develop a bio-nanobattery using ferritins reconstituted with both an iron core (Fe-ferritin) and a cobalt core (Co-ferritin). Both Co-ferritin and Fe-ferritin were synthesized and characterized as candidates for the bio-nanobattery. The reducing capability was determined as well as the half-cell electrical potentials, indicating an electrical output of nearly 0.5 V for the battery cell. Ferritins having other metallic cores are also being investigated, in order to increase the overall electrical output. Two dimensional ferritin arrays were also produced on various substrates, demonstrating the necessary building blocks for the bio-nanobattery. The bio-nanobattery will play a key role in moving to a distributed power storage system for electronic applications.

Our goal was to demonstrate a wireless communications system capable of simultaneous, high speed data communications from a variety of sensors. We have previously reported on the design and application of 2 KHz data logging transceiver nodes, however, only one node may stream data at a time, since all nodes on the network use the same communications frequency. To overcome these limitations, second generation data logging transceivers were developed with software programmable radio frequency (RF) communications. Each node contains on-board memory (2 Mbytes), sensor excitation, instrumentation amplifiers with programmable gains & offsets, multiplexer, 16 bit A/D converter, microcontroller, and frequency agile, bi-directional, frequency shift keyed (FSK) RF serial data link. These systems are capable of continuous data transmission from 26 distinct nodes (902-928 MHz band, 75 kbaud). The system was demonstrated in a compelling structural monitoring application. The National Parks Service requested a means for continual monitoring and recording of sensor data from the Liberty Bell during a move to a new location (Philadelphia, October 2003). Three distinct, frequency agile, wireless sensing nodes were used to detect visible crack shear/opening micromotions, triaxial accelerations, and hairline crack tip strains. The wireless sensors proved to be useful in protecting the Liberty Bell.

The large radar cross section of wind turbine generator (WTG) blades combined with high tip speeds can produce significant Doppler returns when illuminated by a radar. Normally, an air traffic control radar system will filter out large returns from stationary targets, however the Doppler shifts introduced by the WTG are interpreted as moving aircraft that can confuse radar operators and compromise safety. A possible solution to this problem that we are investigating is to incorporate an active layer into the structure of the WTG blades that can be used to dynamically modulate the RCS of the blade return. The active blade can operate in one of two modes: firstly the blade RCS can be modulated to provide a Doppler return that is outside the detectable range of the radar receiver system so that it is rejected: a second mode of operation is to introduce specific coding on to the Doppler returns so that they may be uniquely identified and rejected. The active layer used in the system consists of a frequency selective surface controlled by semiconductor diodes and is a development of techniques that we have developed for active radar absorbers. Results of experimental work using a 10GHz Doppler radar and scale model WTG with active Doppler imparting blades are presented.

Smart liquid crystal (LC) millimeter-wave (MMW) electronic devices are demonstrated using the electrically- controllable permittivity through LC directors’ reorientation. In this paper, we review the LC classes and its important physical properties for the proposed applications. Some commercially available LCs exhibit a relatively large birefringence (Δn~0.2) in MMW bands and, therefore, are useful for millimeter wave devices. A nonradiative dielectric waveguide using LC is proposed and characterized using numerical simulations. The simulation results show that the LC waveguide is promising for future MMW technologies.

Biosensors for detecting and quantifying the presence of a small amount of biological threat agents in a real-time manner are urgently needed for a wide range of applications. In this paper, a novel type of micro-biosensor platform - magnetostrictive microcantilever (MMC) - is reported. The resonance behavior and the sensitivity of MMC are characterized and compared to the theoretical calculation. Additionally, the quality merit factor (Q value) was characterized. It is found: 1) the MMC exhibits a sensitivity of about 50% higher than that of piezoelectric-based microcantilevers and 2) the MMC has a high Q value (~140 in air and 50 in yeast suspension). A biosensor for detecting yeast cells in water is built based on MMC. The performance of the biosensor is characterized.