Polyaniline thin film-porous silicon sensors for detection of microorganisms

Quick and simple methods to detect the type of life threatening microbial species are very essenti al in food and water contaminated with bacteria. Recently, by utili zi ng the semiconducting polymeric thin films prepared on si licon macroporous substrates a new technology for detection of micro-organisms has been developed. The advantages of the polymeric devices are the ease of fabrication , the high sensitivity to micro-organisms, the fast response time and the room temperature operation. In thi s work the current voltage characteristics and the dielectric losses variations of the specifically doped polymeric thin films deposited on silicon macroporous membranes upon exposure to E. Col ii were studied . The sensors were prepared by vacuum depositing doped polyaniline in the form of thin films on the silicon macroporous structures. The particular doping combination in the polymer makes the sensor specific for detection of E. Colii. Moreover the sensitivity of the to E. Colii is very high and the response time of the sensor is about 5 sec. The total response time is a few tens of seconds. The macroporous silicon substrate allows to obtain a polyani line thin film with high specific surface area and good crystallinity, as shown by SEM and X-ray investigations, respectively. Both the high surface area and the crystallinity of the polyaniline film deposited on the macroporous silicon substrate are believed to be responsible for the excellent properties of the sensor device. The fabrication process, the morphological, structural and electrical characterization of the hybrid polymeric/ silicon micro-sensors in regard to detection of E. Colii have been described.