Rapid and selective detection of Staphylococcus aureus using insulated substrate impedance transducers

Tang, Xiaohui [UCL] Flandre, Denis [UCL] Raskin, Jean-Pierre [UCL] Nizet, Yannick [UCL] Moreno-Hagelsieb, L. Pampin, R. Francis, Laurent [UCL] et al.[show all]

We introduce a new insulated substrate impedance transducer (ISIT) for fast, direct, specific and sensitive bacteria detection. The transducer is composed of interdigitated array microelectrodes (IDAM) insulated on a Si substrate by a layer of SiO2. The Al electrodes are protected by a thin layer of Al2O3. It is found that the coupling of target biomolecular charges with the Si substrate free carriers can be sensed capacitively by the insulated interdigitated electrodes, which makes the ISIT more sensitive than the classical IDAM sensor. This opens a new perspective for the future designs of high sensitivity sensors. Less than 240 cells of Staphylococcus aureus (S. aureus) bacteria immobilized on the ISIT sensing area of 200µm× 200µm, lead to significant changes on capacitance and conductance, which can be easily and directly detected in 10 min. The present ISIT also exhibits reproducible specific detection. We investigate the dependence of the ISIT sensitivity on its configuration. The results indicate that for achieving high sensitivity, the ISIT should have a suitable ratio of the interspacing width to the finger width and an interspacing width compatible with the size of the target biomolecule. Besides featuring fast, label-free and low-cost bacteria detection, this ISIT can be used for more applications and can be easily