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A resonant cantilever-based microsystem aimed at biochemical sensing is presented. The sensor system comprises a magnetically actuated resonant cantilever sensor array integrated with the feedback circuitry, digital control circuitry and a serial interface on a single chip in 0.8 [micro]m CMOS technology. The sensor system shows a frequency stability of better than 3 Hz in water corresponding to a detection limit of about 30 pg mass loading. The system has been used for the detection of antibody-antigen interaction on the cantilever surface. The possibility to actuate and operate cantilever arrays in a liquid environment opens up a variety of new applications for bio-chemical sensing. Index Terms--Biosensor, chemical sensor, CMOS, liquid phase, monolithic integration, resonant cantilever.

This paper reports on dc pulse-powered microdischarges in air at atmospheric pressure and their potential utility in chemical sensing. For electrode gaps of 50-100 [micro]m, microdischarges take the form of a glow discharge, an arc discharge, or a hybrid of the two. Arc microdischarges have high optical intensity but suffer from high background emission. Glow microdischarges have low background emission, but the prominent emission is confined in the UV-blue region of the spectrum. The arc--glow hybrid has characteristics that are intermediate between the two and can be tuned by circuitry to suit the chemical sensing application. A handheld system for chemical analysis using synchronized emission spectroscopy of these pulsed microdischarges is demonstrated. The system employs an exchangeable sensor chip (different for gas and liquid samples), a control circuit, and a commercially available portable spectrum analyzer coupled to a handheld computer. A pump and inert carrier gases are not utilized. The system can generate one or a series of single-shot microdischarges per chemical analysis. The gas discharge microchip, which utilizes electroplated copper electrodes on a glass substrate, has an electrode separation of 75 [micro]m and an active area of 300 x 300 [micro][m.sup.2]. The handheld system has been used to detect 17 ppm of acetone vapor in air. The liquid discharge microchip also has an electrode gap of 75 [micro]m and an active area of 1 x 1 [mm.sup.2]. It uses a porous cathode fabricated by micromolding and sintering glass frit slurry in a microchannel. When a microdischarge is initiated between the metal anode and the wet cathode, the liquid is sputtered into the microdischarge and emits characteristic line spectra. In this configuration, the system can detect 2 ppm of aqueous Cr without preconcentration. Index Terms--Chemical sensing systems, gas detectors, gas discharge devices, microarc, microdischarge, microplasma, water chemistry.

The design and development of a phase fluorometric oxygen ([O.sub.2]) sensor system using single-chip CMOS detection and processing integrated circuit (DPIC) and sol-gel derived xerogel thin-film sensor elements is described. The sensor system determines analyte concentrations using the excited state lifetime measurements of an [O.sub.2]-sensitive luminophore (tris(4,7-diphenyl-1, 10-phenathroline)ruthenium (II)) embedded in the xerogel matrix. A light emitting diode (LED) is used as the excitation source, and the fluorescence is detected by the DPIC using a 16 x 16 phototransistor array on-chip. The DPIC also consists of a current mirror, current-to-voltage converter, amplifier, bandpass filter, and phase detector. The DPIC output is a dc voltage that corresponds to the detected fluorescence phase shift. With a 14-kHz modulation frequency, the entire system including driving the LED consumes 80 mW of average power. The sensor system provides stable, reproducible, analytically reliable, and fast response (~ 20 s) to changes in the gaseous oxygen concentrations and establishes the viability for low cost, low power and miniaturized biochemical sensor systems. Index Terms--Chemical sensor, CMOS, frequency response, lifetime sensors, oxygen sensor, phase angle, phase fluorometry, phototransistor, sensor integration, signal processing, sol-gel, VLSI, wavelength response, xerogel.

In this paper, we present the analog circuit design and implementation of the components of an adaptive neuromorphic olfaction chip. A chemical sensor array employing carbon black composite sensing materials with integrated signal processing circuitry forms the front end of the chip. The sensor signal processing circuitry includes a dc offset cancellation circuit to ameliorate loss of measurement range associated with chemical sensors. Drawing inspiration from biological olfactory systems, the analog circuits used to process signals from the on-chip odor sensors make use of temporal 'spiking' signals to act as carriers of odor information. An on-chip spike time dependent learning circuit is integrated to dynamically adapt weights for odor detection and classification. All the component subsystems implemented on chip have been successfully tested in silicon. Index Terms--Analog VLSI, electronic nose, machine olfaction, neuromorphic circuits, on-chip learning, spike-timing-dependent plasticity (STDP).

A novel optical-fiber sensor is proposed for use in chemical analysis. The sensor probe is made of a gold-coated multimode optical fiber, configured to exhibit surface plasmon resonance (SPR) when immersed in a wet environment. The proposed detection strategy comprises measurement of the image pattern irradiated by the fiber under monochromatic illumination. A theoretical model is proposed to determine device performance. From computer simulations, it is shown that the proposed configuration and detection strategy allows reaching a 30-fold enhancement in sensitivity relative to that obtained in previous SPR-based versions of the device. Index Terms--Chemical sensor, fiber sensor, gold, SPR, surface plasmon.

We report the status of ongoing investigations into Cadmium Zinc Telluride (CZT) strip detectors for application in hard x-ray astronomy. We have instrumented a nine strip by nine strip region of a two sided strip detector made in our detector fabrication facility. In order to measure the position resolution of our detectors, we have implemented a collimated beam that concentrates radiation to a spot size less than 50 [[micro]meter]. We have placed a 30 [[micro]meter] upper limit on the width of the point spread function for this system. We have also performed charge collection studies as a function of incident photon energy and bias voltage with a single sided, 100 [[micro]meter] pitch CZT strip detector wire bonded to an SVX ASIC charge amplifier. The detectors exhibited excellent strip uniformity in terms of photon count rate and spectroscopic information.

Three types of ceramic sensors namely solid electrolyte gas, semiconductor gas and capacitor-type gas sensors based on solid electrolytes and semiconducting oxides are developed to detect gaseous environmental pollutants such as CO2, NO, NO2, SOx, O3, NH3 and H2S. The oxygenic gases are detected using solid electrolyte gas sensors. Semiconductor gas sensors are useful in detection of offensive odorants and ozone. The design and construction of semiconductor gas sensors is difficult as it is dependent on materials and microstructures used.

A new type of continuously operating, in-situ, remotely monitored sensor is presented. The sensor is comprised of a thin film array of magnetostatically coupled, magnetically soft ferromagnetic thin film structures, adhered to or encased within a thin polymer layer. The polymer is made so that it swells or shrinks in response to the chemical analyte of interest, which in this case is pH. As the polymer swells or shrinks, the magnetostatic coupling between the magnetic elements changes, resulting in changes in the magnetic switching characteristics of the sensor. Placed within a sinusoidal magnetic field the magnetization vector of the coupled sensor elements periodically reverses directions, generating magnetic flux that can be remotely detected as a series of voltage spikes in appropriately placed pickup coils. One preliminary sensor design consists of four triangles, initially spaced [approximately equal to] 50 [[micro]meter] apart, arranged to form a 12 mm x 12 mm square with the triangle tips centered at a common origin. Our preliminary work has focused on monitoring of pH using a lightly crosslinked pH sensitive polymer layer of hydroxyethylmethacrylate and 2-(dimethylamino) ethylmethacrylate. As the polymer swells or shrinks the magnetostatic coupling between the triangles changes, resulting in measurable changes in the amplitude of the detected voltage spikes. Index terms - Chemical Sensor, Remote Telemetry, Magnetochemical.

We have developed a phoswich detector composed of a plastic scintillator and a BGO scintillator for a continuous blood-sampling system. The beta particle (positron) from the tube is detected by the plastic scintillator and emits 511-keV gamma photons. The BGO scintillator that is optically coupled to the plastic scintillator detects one of the gamma photons. Since the decay time of the plastic scintillator and the BGO are very different, it is possible to discriminate true (beta + gamma) events from background gamma events. First, the pulse height and pulse shape of plastic scintillator for beta particles and BGO scintillator for 511-keV gamma photons were measured and compared to estimate the possibility of the proposed method. Second, the proposed phoswich detector was fabricated and tested. Absolute sensitivity for Ga-68 (maximum energy of 1.90 MeV) and F-18 (maximum energy of 633 keV) positrons was measured and compared with conventional beta detector of similar size. The absolute sensitivity of the developed detector was 0.15 counts/Bq for Ga-68 positrons at the center of the detector. This was approximately five times higher in sensitivity than the conventional beta detector. The absolute sensitivity of the developed detector for F-18 positrons was 0.017 counts/Bq. The count rate of the developed detector was linear up to 10 kcps. The background count rate was small. These results indicate that the developed detector is useful not only for higher energy positrons such as O-15 but also for lower energy positrons such as F-18 or C-11. Index Terms--Continuous blood sampling, gamma photon, phoswich detector, positron.