Calibration curve-free electrochemical quantitation by micro-nano multi-scale gap devices.

Quantitation without relying on the calibration curve has long been an issue of overcoming analytical problems accompanied with the inherent limitations of the calibration curve fitting errors. Here, we report on a calibration curve-free method for electrochemical quantitation based on a multi-scale gap device (MGD). The MGD is an integrated device having a series of interdigitated electrodes (IDE) with micro-to-nano gap distances.

Electrical Detection of Pneumococcus through the Nanoparticle Decoration Method.

A simple method of nanoparticle decoration can be used in the detection of pneumococcus. After the pneumococcal bacteria were captured by an antibody (pneumococcal C-polysaccharide (PnC) antibody) between the interdigitated electrodes, the gold nanoparticles conjugated with the PnC antibodies were let to bind onto an outer membrane of the bacteria. Upon successfully dense decoration, the bacteria surface will become conductive owing to the metal nanoparticles, and a distinctive conductance change between the electrodes can be observed.

Quantification of antigen by digital domain analysis of integrated nanogap biosensors.

Nanogap biosensor shows a distinct conduction change upon sandwich-type immobilization of gold nanoparticle probes onto the gap region in the presence of target biomolecules. Although this large conductance change could be advantageous in distinguishing signal on or off devices, since the extent of conductance change is quite irregular even at the same analyte concentrations, it fails to extract quantitative information from its level of conductance change. In other words, the conductance change of a single device does not reflect the concentration of the target molecule.

Nanogap-based electrical PNA chips for the detection of genetic polymorphism of cytochrome P450 2C19.

PNA chips for the detection of the genetic polymorphism of Cytochrome P450 2C19 (CYP2C19), a well-known enzyme related to the metabolism of therapeutic drugs, were electrically-interfaced with interdigitated nanogap electrodes (INEs). The average gap distance and effective length of the INEs were about approximately 70 nm and approximately 140/m, respectively. Those INEs having the aspect ratio of about 2000, were prepared by the combination of the photolithography (for the formation of initial electrodes) and the surface-catalyzed chemical deposition (for the gap narrowing), without the e-beam lithography.

Superhydrophobic thin films with nanostructured surface prepared with Au nanoparticle masks.

The hydrophobicity of a perfluoropolyether bisurethane methacrylate polymer film was investigated along with the formation of nano-hairs on its surface through reactive ion etching using gold nanoparticles (Au NPs) as masks. It was found that the hydrophobicity of the polymer film was strongly dependent on the number density of the nano-hairs which was determined by that of the Au NPs. The superhydrophobic surface was obtained when the number density was higher than 250 microm(-2).

Control of nanogap separation by surface-catalyzed chemical deposition.

The nanogap devices, which comprise multiple electrodes separated by a few to a few tens of nanometers, have opened up new possibilities in biomolecular sensing as well as various frontier electronics. One of the key aspects of the nanogap device research is how to control the gap distance following each specific needs of the gap structure. Here, we report the extensive study on the fine control of the gap distance between electrodes within the range of 1-80 nm via surface-catalyzed chemical deposition.