Arrays of highly ordered n-type silicon nanowires (SiNW) are fabricated using complementary metal-oxide semiconductor (CMOS) compatible technology, and their applications in biosensors are investigated. Peptide nucleic acid (PNA) capture probe-functionalized SiNW arrays show a concentration-dependent resistance change upon hybridization to complementary target DNA that is linear over a large dynamic range with a detection limit of 10 fM. As with other SiNW biosensing devices, the sensing mechanism can be understood in terms of the change in charge density at the SiNW surface after hybridization, the so-called "field effect". The SiNW array biosensor discriminates satisfactorily against mismatched target DNA. It is also able to monitor directly the DNA hybridization event in situ and in real time. The SiNW array biosensor described here is ultrasensitive, non-radioactive, and more importantly, label-free, and is of particular importance to the development of gene expression profiling tools and point-of-care applications.

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Arrays of highly ordered silicon nanowire (SiNW) clusters are fabricated using complementary metal-oxide semiconductor (CMOS) field effect transistor-compatible technology, and the ultrasensitive, label-free, electrical detection of cardiac biomarker in real time using the array sensor is presented. The successful detection of human cardiac troponin-T (cTnT) has been demonstrated in an assay buffer solution of concentration down to 1 fg/mL, as well as in an undiluted human serum environment of concentration as low as 30 fg/mL. The high specificity, selectivity, and swift response time of the SiNWs to the presence of ultralow concentrations of a target protein in a biological analyte solution, even in the presence of a high total protein concentration, paves the way for the development of a medical diagnostic system for point-of-care application that is able to provide an early and accurate indication of cardiac cellular necrosis.

To provide a comprehensive understanding of the field effect in silicon nanowire (SiNW) sensors, we take a systematic approach to fine tune the distance of a charge layer by controlling the hybridization sites of DNA to the SiNW preimmobilized with peptide nucleic acid (PNA) capture probes. Six target DNAs of the same length, but differentiated successively by three bases in the complementary segment, are hybridized to the PNA. Fluorescent images show that the hybridization occurs exclusively on the SiNW surface between the target DNAs and the PNA. However, the field-effect response of the SiNW sensor decreases as the DNA (charge layer) moves away from the SiNW surface. Theoretical analysis shows that the field effect of the SiNW sensor relies primarily on the location of the charge layer. A maximum of 102% change in resistance is estimated based on the shortest distance of the DNA charge layer (4.7 A) to the SiNW surface.

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Perfectly aligned arrays of long silicon nanowires fabricated using a top–down complementary metal oxide semiconductor (CMOS) compatible approach and their ability for real‐time extracellular recording of cellular bioelectricity are presented. The technique enables noninvasive, high‐sensitivity, high‐throughput, long‐term electrophysiology measurements at the single‐cell level or from tissues.

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