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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.

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).