In the last few years there has been a huge demand to monitor different chemical environments, such as for example urban indoor and outdoor atmospheres, food aromas, etc. Chemical Optical sensors are among the most promising devices to be exploited for these kind of applications. Nonetheless, the chemical practice of this approach is badly balanced by the transducer counterpart. Indeed, traditional optical instrumentations of high quality are usually bulky and expensive. On the other side in the last decade, in spite of the high cost of optical instruments, we assisted to a fast growth of performance in fields as consuming electronics, giving rise to a number of low-cost advanced optical equipments such as digital scanners, cameras, and screens whose characteristics largely fit the requirements necessary to capture change of optical properties of sensitive layers in many practical applications, that could be usefully exploited in routine analysis. In this thesis will be demonstrated that a combination of a computer monitor and an inexpensive webcam may be turned into a sort of spectrophotometer instrument. This last technique, known as Computer Screen Photo assisted Technique (CSPT) is based on the fact that a computer screen can be easily programmed to display millions of colour, combining wavelengths in the optical range. The CSPT is a sensing method that allows regular computer screens and web cameras to operate as generic sensing platforms of optical (bio)chemical assays. Due to the large diffusion of portable computers, PDAs, and cellular phones all endowed with colour screen, camera, and an even more extended computation capabilities, the application of the CSPT concept may be foreseen as to give rise to a sort of ubiquitous analytical capacity. During a CSPT measurement the screen illuminates the array with an appropriate sequence of colours, while the webcamera captures the image of the array under analysis in synchronism with the illumination. The result of this data acquisition is a video stream, where regions of interest (ROIs) are selected and the intensity of the recorded pixels averaged into these regions chosen by us. The procedure is repeated along all N (length of the colour sequence) frames, generally corresponding to an illuminating sequence resembling the human perception of the visible spectrum. In this way a N elements vector is obtained for each ROI and camera channel. A fingerprint of the complete array is often constructed by concatenating red, green and blue channel vectors of each ROI and subsequently by collecting the different ROI vectors in a single (N*M*3) elements vector, where N is the length of the colour sequence, M is the number of the ROIs selected and 3 is the number of camera channel (Red, Green and Blue). Then CSPT could in principle be used to detect general parameters related to the absorbance-emission spectra of every material under observation. In this Thesis, we show the possibility to use this very simple platform (CSPT), in two different configuration (Enose-mode and Spectroscopy mode), for very different kind of applications. In fact, in the first case, we present a chemical gas sensor array for detection of volatile molecules (NOx, CO, TEA, ETOH etc), and of fish freshness, where the optical features of layers of chemicals are transduced by CSPT-Enose mode; while in the second case we highlight the potentiality to use the CSPT such as a spectrophotometer, to directly optical characterize the compounds that we are observing (in this Thesis, Wine Optical Properties detection, and Bilirubin analysis will be showed).
Alimelli, A. (2009). Analytical system with familiar devices engineering.
|Titolo:||Analytical system with familiar devices engineering|
|Data di pubblicazione:||30-lug-2009|
|Anno Accademico:||A.A. 2006/2007|
|Corso di dottorato:||Sensorial and learning systems engineering|
|Settore Scientifico Disciplinare:||Settore ING-INF/01 - Elettronica|
|Tipologia:||Tesi di dottorato|
|Citazione:||Alimelli, A. (2009). Analytical system with familiar devices engineering.|
|Appare nelle tipologie:||07 - Tesi di dottorato|