A new interdigitated array microelectrode-oxide-silicon sensor with label-free, high sensitivity and specificity for fast bacteria detection

We introduce a new interdigitated array microelectrode-oxide-silicon (IDAMOS) sensor with label-free, high sensitivity and specificity for fast bacteria detection. The sensor is composed of Al interdigitated array microelectrodes (IDAM) insulated from an active Si substrate by a layer of SiO2. The Al microelectrodes are protected by a thin layer of Al2O3. It is found that charged target molecules deposited on the IDAM surface can modify the space-charge region properties in the active Si substrate through metal-oxide-semiconductor (MOS) capacitor effect, which makes the new sensor more sensitive than the classical IDAM sensor. This opens a new perspective for the future designs of highly sensitive sensors. We investigate the dependence of the IDAMOS sensor sensitivity on its electrode size. The results indicate that for achieving high sensitivity, the IDAMOS sensor should have a suitable ratio of the interspacing width to the electrode width and an interspacing width compatible with the size of the target biomolecule. Staphylococcus aureus is used as a test system to establish the sensitivity and specificity of the IDAMOS sensor. Less than 240 bacteria cells immobilized on the IDAMOS sensing area of 200 μm × 200 μm, leads to significant changes on capacitance and conductance, which can be easily and directly detected in 10 min. Besides featuring rapid, specific, free-label and low-cost bacterial detection, this IDAMOS sensor can be used for more applications and can be easily integrated with complementary metal-oxide-semiconductor circuits. The fabrication process of the IDAMOS sensor is reproducible, reliable and valid for large-scale products.