B. Margesin

Development of ISFET array-based microsystems for bioelectrochemical measurements of cell populations

Monitoring the bioelectrochemical activity of living cells with sensor array-based microsystems represents an emerging technique in a large area of biomedical applications, ranging from basic research to various fields of pharmacological analyses. The main appeal is the ability of these miniaturised microsystems to perform, in real time, non-invasive in-vitro investigations of the physiological state of a cell population. In this paper, we present two different microsystems designed for multisite monitoring of the physiological state of a cell population. The first microsystem, intended for cellular metabolism monitoring, consists of an array of 12 spatially distributed ISFETs to detect small pH variations induced by the cell population. The second microsystem consists of an array of 40 ISFETs and 20 gold microelectrodes and it has been designed to monitor the electrical activity of neurons. This is achieved by direct coupling of the neuronal culture with the ISFET sensitive layer and by utilising gold microelectrodes for neuronal electrical stimulation.

Bioelectrochemical signal monitoring of in-vitro cultured cells by means of an automated microsystem based on solid state sensor-array

In the last decade, fundamental advances in whole cell based sensors and microsystems have established the extracellular acidification rate monitoring of cell cultures as an important indicator of the global cellular metabolism. Innovative approaches adopting advanced integrated sensor array-based microsystems represent an emerging technique with numerous biomedical applications. This paper reports a cell-based microsystem, for multisite monitoring of the physiological state of cell populations. The functional components of the microsystem are an ion sensitive field effect transistor (ISFET) array-based sensor chip and a CMOS integrated circuit for signal conditioning and sensor signal multiplexing. In order to validate the microsystem capabilities for in-vitro toxicity screening applications, preliminary experimental measurements with Cheratinocytes, and CHO cells are presented. Variations in the acidification rate, imputable to the inhibitory effect of the drug on the metabolic cell activity have been monitored and cell viability during long term measurements has been also demonstrated.

Polysilicon mesoscopic wires coated by Pd as high sensitivity H2 sensors

A new class of H2 sensors made up of mesoscopic polysilicon wires coated by palladium is presented. Using surface micromachining combined with an usual microelectronic planar process, polysilicon wires of the following dimensions have been constructed: from 250 nm up to 3.7 µm wide, from 100 µm up to 140 µm long, about 700 nm thick. Because of their high surface/volume ratio, these wires have shown a very high resistance percentage variation under hydrogen absorption. Enhanced resolution together with a low production cost are the most important feature of this device.

An H+-FET-based system for on-line detection of microorganisms in waters

Abstract A flow-through system for on-line detection of microorganisms in waters is presented. A Si3N4 ISFET with integrated signal-conditioning electronics, expressly designed for this application, is employed as an H+ sensor. The article describes the system principles, the transducer architecture, a preliminary characterization of the developed sensor chip, and preliminary measurements performed in the presence of microorganisms.

MOS-junction-based nanostructures by thermal oxidation of silicon wires for hydrogen detection

Heavily p-doped monocrystalline silicon wires have been fabricated by employing isotropic Si wet etch and thermal oxidation to achieve a nanometric cross section-a gate-oxide growth and a final palladium evaporation made up the MOS junction able to detect hydrogen concentration in air. Several types of wire dimensions have been designed and fabricated: length ranges from 5 to 70 /spl mu/m; the smallest widths obtained are around 250-300 nm, while the biggest are up to 7 /spl mu/m. Preliminary experimental results show a high signal/noise ratio sensor response to 100 ppm concentration of H/sub 2/ at room temperature, 1-atm air.

MOS junction based nanostructures by thermal oxidation of silicon wires for hydrogen detection

Heavily p-doped monocrystalline silicon wires have been fabricated by employing wet etch and thermal oxidation steps to achieve a nanometric cross-section; a gate oxide growth and a final palladium evaporation made up the MOS junction able to detect hydrogen concentrations in air.

POLYSILICON MESOSCOPIC WIRES COATED BY Pd AS H2 SENSORS

In this work a novel monocrystalline silicon nanowires array has been investigated and presented as hydrogen sensor, designed and fabricated by employing high resolution microfabrication techniques ...