A. Alimelli

An integrated analog lock-in amplifier for low-voltage low-frequency sensor interface

In this paper we propose a low single supply voltage (2V) analog lock-in amplifier, completely integrable on silicon, designed in a standard CMOS technology, for electronic sensor interfaces used in low-frequency applications. In particular, the proposed architecture is suitable for those sensor interfaces where the signal to be measured has a small amplitude and is buried into noise. In these cases, the lock-in amplifier guarantees the signal recovery from noise (till to 0.1 SNR), provided that the generated small signal, coming from sensor, has a fixed and well-known frequency. Together with the integrated solution, waiting for the chip fabrication, we have built a discrete element board, with commercial components, for preliminary experiments which confirm the validity of the proposed lock-in system, since it is able to detect, for example, very small quantities of carbon monoxide (CO).

Development of porphyrins based sensors to measure the biological damage of carbon monoxide exposure

The oxygen transport in blood is threatened by the presence of carbon monoxide. CO indeed permanently replaces the oxygen molecule in the hemoglobin making this last no more effective as oxygen carrier. This mechanism is ruled by the properties of a particular metalloporphyrin (heme) for which the binding energy with CO is about 250 times higher than that towards O/sub 2/. In this paper, a sensor system based on the properties of metallaporphyrins with a colorimetric read-out is illustrated. This system is shown to be sensitive both to the concentration of CO and to the exposure time giving rise to the evaluation of the biological damage of carbon monoxide. Results shown a good accuracy of the carboxy-hemoglobin (HbCO) percentage, calculated with a standard reference model, achieving a standard error of 1%. This value is well below the amount of HbCO known to produce either acute or chronic effects on human beings.

Spectral fingerprinting of porphyrins for distributed chemical sensing

Recent progress in spectral fingerprinting of fluorescent indicators using distributed instrumentation based on consumer electronic devices is reviewed. In particular, the evaluation of disposable assays using a computer screen photo-assisted technique (CSPT) is discussed. Sample identification and optimization strategies are analyzed as well as the underlying theoretical background for polychromatic spectral fingerprinting.