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FP5

SPOT-NOSED Report Summary

Project ID: IST-2001-38899
Funded under: FP5-IST
Country: Italy

Prototype of a full custom electronic instrumentation system for electrochemical measurements at the nanoscale

There exist in the market available electronic instrumentation for electrochemical characterisation of a wide variety of samples. Among them we cite the equipments used inside the present project for the characterisation of the microtransducers: The Voltalab system sensibility is intended for measurements at the milimeter scale, while brand new systems are intended for more sensitive measurements and hence adequate for measurements at the micro/nanoscale. However, these last systems even if powerful are very expensive and not very versatile hence not suitable for the development of a practical biosensor

For these reasons, we have developed a full custom electrochemical electronic instrumentation for the measurements with the micro/nanotransducers developed inside the project.

The measuring system consists on an electronic front-end setting and reading the signals in the Control Electrode, in the Working Electrode and in the Reference Electrode, featuring a special circuitry for spurious current compensation due to interelectrode capacitance of any value.

Two electronic front-ends have been fabricated in order to adapt the instrumentation both for microelectrodes and nanoelectrodes. The front-end for the microelectrodes can draw a maximum DC current of 1µA with a signal bandwidth of 2MHz. For the nanoelectrodes a second front-end has been fabricated with ten times less instrumental noise increasing proportionally the sensitivity. The disadvantage of this solution is a reduced maximum DC current (10nA) and signal bandwidth (0.9MHz).

The electronic front-ends are miniaturised to be lodged close to the electrochemical cell, and are followed by the control electronic stage providing more amplification, the power supply and the electronic interface to connect with a PC for automatic control.

The connection to the nanoelectrodes has been optimised with a proper board that allows an easy fit of the nanochip into the electrochemical cell.

The fabricated instrument is controlled by a PC with a data acquisition board and can perform both cyclic voltammetry (resolution of 40fA at the maximum speed of 1V/s) and impedance spectroscopy (signal bandwidth 1Hz 0.9MHz, tens of attoFarad of capacitance resolution).

Software to control the instrumentation for electrochemical measurement has also been realised.

The main features are:
- Generation and acquisition of the signals for cyclic voltammetry; all parameters for the measurement (voltage curve, speed, number of cycles) are easily selectable;
- Visualisation of the voltammetry measurements with different filters to reduce spurious noise;
- Generation and acquisition of the signals for electrochemical impedance spectroscopy; all parameters for the measurement (dc bias, ac amplitude, frequency range, averaging time) are easily selectable;
- Visualisation of the impedance measurements as a Cole-Cole plot (real part vs imaginary part of the impedance) or as a Bode plot (impedance module and phase as a function of the frequency);
- Automatic calibration of the instrument to compensate phase shift due to the cables and the PoliMi amplifier;
- Tracking the time evolution of the impedance at a single frequency;
- All the measurements are available in standard ASCII format.

Related information

Reported by

POLITECNICO DI MILANO
Piazza Leonardo Da Vinci, 32
20133 MILANO
Italy
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