Fabrication and testing of interdigitated microelectrode arrays whose structure includes non-cytotoxic hydrogenated amorphous silicon-carbon alloy (a-Si x C 1-x :H) as the surface to be biofunctionalized for capturing enteropathogenic Escherichia coli (E. coli, EPEC) are presented. a-Si x C 1-x :H films were obtained by enhanced chemical vapor deposition (PECVD). The extract method was used to assess the cytotoxicity of the films. The design of the PIMAs includes two layers of a-Si x C 1-x :H, one intrinsic layer deposited onto silicon dioxide (SiO 2 ) before evaporating titanium (Ti), and one doped layer deposited onto the Ti-microelectrodes. Electrical impedance spectroscopy (EIS) was used to know the effects of the biofunctionalization layer, conductivity of the medium and any capture of bacteria by antibodies on the microelectrodes. According to the results, the high hydrogen dilution contributes to low incorporation of CH n groups improving the non cytotoxicity of the films, and the capture of bacteria on the microelectrodes improves the sensitivity. It manifests itself as a shift of the low cutoff frequency (F low ) of the impedance spectrum to the right, allowing the device to sense at frequencies lower than F low . A percentage change in impedance of 1600% at 100 Hz was obtained after 5 minutes in contact with medium with EPEC concentration of 8.5 × 10 8 CFU/mL.

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The design and simulation of a biosensor based on interdigitated microelectrodes for bacteria detection is presented. The biosensor includes a microchannel to ensure the flow of the sample through the space between microelectrodes, where the surface is biofunctionalized with antibodies to capture the bacteria. The design was built on COMSOL Multiphysics® software. The effects of the microelectrode thickness and the channel depth on the biosensor sensitivity were studied by simulation. There is a specific microelectrode thickness at which the sensitivity is maximum for Escherichia coli. The microchannel depth affects the sensitivity of the device when it is below 10 μm, approximately. The sensitivity increases when the biosensor is made with low-permittivity materials. A maximum percentage change in capacitance of around 46% was obtained by covering the total sensing area with bacteria.