Polymer-protected sub-2-nm-nanogap fabrication for biological sensing in near-physiological conditions.

There has been considerable interest in developing methods for rapid and sensitive detection of biological molecules such as DNA and proteins in biodefense and drug-discovery applications. Fluorescence-based optical-detection methods are widely used in various settings, but these methods require labeling of the target molecules and generally exhibit a relatively low detection sensitivity and thus are not suitable for rapid and inexpensive detection of small quantities of target molecules. Electrical detection schemes have recently gained significant attention because they are label-free and capable of rapidly detecting minuscule quantities of molecules. Among electrical-based detection methods, nanogap devices that comprise a pair of electrodes with separations on the order of nanometers have been intensively investigated. Several approaches, including nanoimprinting, electron-beam lithography, dip-pen lithography, shadow masking, electrochemical etching/deposition,