Macroporous silicon as an interdigitated electrode-less platform for impedance based bacteria detection

In this paper, an interdigitated electrode-less, high performance macroporous silicon based impedance biosensor has been reported for the detection of bacteria mainly E.Coli O157 and Salmonella Typhimurium. Macroporous silicon of three different pore thickness and 55% porosity have been fabricated on a 10-20 Ω-cm wafer using electrochemical etching. The samples are then thermally oxidized for partial oxidation of silicon crystallites followed by optimized silanization and antibody immobilization. Two simple gold coated aluminium electrodes of 2 mm by 1 mm dimensions and 1mm spacing have been fabricated. It has been observed that the macroporous silicon with 8μm thickness exhibits the maximum sensitivity of 30% corresponding to 10⁴ CFU/ml of E.Coli O157 which is two times more than the sensitivity obtained with other thickness of macroporous silicon for Salmonella Typhimurium. The optimized sensor is also improved compared to most of the other reports using IDE structures. The optimized sensor has been found to be reproducible, specific and capable of detecting down to 10³ CFU/ml with a simple structure.