Polyaniline thin film-porous silicon sensors for detection of microorganisms

Quick and simple methods to detect the type of life threatening microbial s pecies are very essential in food and water contaminated with bacteria. Rec ently, by utilizing the semiconducting polymeric thin films prepared on sil icon macroporous substrates a new technology for detection of micro-organis ms 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 this work the current voltage characteristics and the dielectric losses variations of the specifically do ped polymeric thin films deposited on silicon macroporous, membranes upon e xposure to E. Colii were studied. The sensors were prepared by vacuum depos iting doped polyaniline, in the form of thin films on the silicon macroporo us structures. The particular doping combination in the polymer makes the s ensor specific for detection of E. Colii. Moreover the sensitivity of the t o E. Cold is very high and the response time of the sensor is about 5 see, The total response time is a few tens of seconds. The macroporous silicon s ubstrate allows to obtain a polyaniline thin film with high specific surfac e area and good crystallinity, as shown by SEM and X-ray investigations, re spectively. Both the high surface area and the crystallinity of the polyani line film deposited on the macroporous silicon substrate are believed to be responsible for the excellent properties of the sensor device. The fabrica tion process, the morphological, structural and electrical characterization of the hybrid polymeric/silicon micro-sensors in regard to detection of E. Colii have been described.