Rémi Pampin

Immobilization of DNA on CMOS compatible materials

The main interface and interconnection materials normally used in complementary metal-oxide semiconductor (CMOS) integrated circuit processing, i.e. silicon oxides and aluminum, were evaluated with regards to deoxyribonucleic acid (DNA) attachment. We investigated and quantified the influence of various techniques of fabrication of the silicon oxide on DNA binding obtained by four different biochemical processes. Regarding aluminum, we found that it only binds DNA in the presence of its natural oxide and that it is severely degraded by one of the three typical biochemical processes. Optimal process conditions for DNA binding on silicon oxides with aluminum compatibility are finally derived

Miniaturized Wireless Sensing System for Real-Time Breath Activity Recording

A portable, non-invasive and easy to operate wireless system has been developed for monitoring the breathing activity of patient. The system is composed of a capacitive microsensor (airflow-humidity sensor) integrated on a silicon chip and of a Negative Temperature Coefficient thermistor; both are connected to a wireless network to allow efficient healthcare at home as well as in hospitals. The capacitive sensitive part of the microsensor is an array of interdigitated metallic electrodes covered by 100-nm-thick dense anodized aluminum oxide layer. The breath water vapor is adsorbed over the interdigitated electrodes and changes the sensor characteristic capacitance by up to two orders of magnitude. This modulated signal is then digitized and either stored in a memory or directly transmitted to a monitor through a short distance radio frequency (RF) link. Results show that the wireless platform can be powered by two AAA batteries and deployed in a mesh or star configuration as wireless sensor network. Full size of the microsensor is less than 1 cm2 and is conveniently implemented in a classical adhesive bandage or in nasal prongs. This microsystem is proposed for monitoring sleep-disordered breathing as well as breathing rhythm of athletes during effort.

Direct protein detection with a nano-interdigitated array gate MOSFET.

A new protein sensor is demonstrated by replacing the gate of a metal oxide semiconductor field effect transistor (MOSFET) with a nano-interdigitated array (nIDA). The sensor is able to detect the binding reaction of a typical antibody Ixodes ricinus immunosuppressor (anti-Iris) protein at a concentration lower than 1 ng/ml. The sensor exhibits a high selectivity and reproducible specific detection. We provide a simple model that describes the behavior of the sensor and explains the origin of its high sensitivity. The simulated and experimental results indicate that the drain current of nIDA-gate MOSFET sensor is significantly increased with the successive binding of the thiol layer, Iris and anti-Iris protein layers. It is found that the sensor detection limit can be improved by well optimizing the geometrical parameters of nIDA-gate MOSFET. This nanobiosensor, with real-time and label-free capabilities, can easily be used for the detection of other proteins, DNA, virus and cancer markers. Moreover, an on-chip associated electronics nearby the sensor can be integrated since its fabrication is compatible with complementary metal oxide semiconductor (CMOS) technology.

Fluid characterization by interdigitated electrodes sensors

The purpose of this paper is to present the concept of a complete fluid characterization microsystem. This system is composed of three parts. The first is a classical two-dimensional sensor using interdigitated (IDA) aluminum electrodes covered by anodized alumina. The second part is a CMOS digital circuit which is used to modulate the sensor topology. The work of the last part is to transduce the sensor useful signal in an oscillating voltage.

On-Chip RF Detection of DNA Hybridization Based on Interdigitated Al/Al2O3 Capacitors

On-chip hybridization of very low concentrations of single-strand DNA targets has been detected by RF electrical measurements of interdigitated aluminum electrodes covered by Al2O3 and gold nano-labels around which silver precipitation is performed for signal enhancement The extraction procedure is based on the detection of the interdigitated capacitor self-resonance frequency through the wideband measurement of its inter-electrodes capacitance. Results show an excellent correlation between the sensing area covered by the silver grains, the low-frequency capacitance value and the self-resonance frequency change. Significant self-resonance frequency shifts for the proposed capacitive sensor are still measured for target DNA concentration as low as 50 pM. Based on these experimental results, the great capability of the present method is demonstrated and potential improvements are proposed to detect even lower DNA concentrations

DNA detection based on capacitive AL/sub 2/O/sub 3//AL microelectrodes

The electrical detection of DNA hybridization still faces the challenge of detecting very low concentrations. In this work we present the possibility of detecting DNA probes by measuring a capacitance change between interdigitated aluminum micro-fingers coated with a thin alumina layer and constructed over an oxidized silicon wafer. DNA Labeling was performed by biotinylated nucleotides and reaction with anti-biotin/gold nanoparticles, increased in size by silver crystal precipitation. The capacitance change ratio observed was at least of two, using 0.2 nM DNA solutions. This detection method appears compatible with microarray technology and paves the way for further use in biological applications.

Bio-compatible Insulated Substrate Impedance Transducers

An alternative smart sensing paradigm to largescale biocompatible integration has been explored. Traditionally, conductive bio-labels detection profits from planar interdigitated electrodes (IDE) encapsulated between for instance a top thin alumina layer and a bottom thick silicon dioxide. Despite demonstrating good electrostatic sensitivity at strong micro-labels densities, such patterns however require sub-micron shrinking to work below 30% conductive labels coverage. We therefore derived a spectroscopic field-effect transducer from micrometric DDE coupled to a thinly insulated surface-doped silicon channel. Thanks to capacitance enhancement that results between electrodes and semiconductor, label-induced field-effect modulation of channels conductance gives rise to an intrinsic dielectric relaxation constant change subsequently measured by impedance spectroscopy. So-called Insulated Substrate Impedance Transducers (ISIT) have thereby been designed to sense an inter-digital impedance spectrum change following a frequency-dependent multi-parameter approach. In demonstration, metallic grains densities ranging from 1.2% to 17%, ensued from 0 to 1 nM concentrations of silver-labeled 30 bp DNA targets were sensed in air on 100 * 100 mu m/sup 2/ arrays through conductance and capacitance variations by factors of 6 and 3, respectively. Our presentation will focus on simulation, optimization and characterization of ISITs electrical operation, and present on-chip tuning possibilities associated with substrate back-contact biasing.