No abstract

We have used a resonating mechanical cantilever to detect immunospecific binding of viruses, captured from liquid. As a model virus, we used a nonpathogenic insect baculovirus to test the ability to specifically bind and detect small numbers of virus particles. Arrays of surface micromachined, antibody-coated polycrystalline silicon nanomechanical cantilever beams were used to detect binding from various concentrations of baculoviruses in a buffer solution. Because of their small mass, the 0.5 µm x 6 µm cantilevers have mass sensitivities on the order of 10-19 g/Hz, enabling the detection of an immobilized AcV1 antibody monolayer corresponding to a mass of about 3 x 10-15 g. With these devices we can detect the mass of a single virus particles bound to the cantilever. Resonant frequency shift resulting from the adsorbed mass of the virus particles distinguished solutions of virus concentrations varying between 10 5 and 10 7 pfu/ml. Control experiments using buffer solutions without baculovirus showed small amounts (< 50 attograms) of non-specific adsorption to the antibody layer. Summary: High frequency nanoelectromechanical systems [1-4] (NEMS) are being considered as new sensors and devices. They may perform with increased speed and sensitivity in chemical, and biological sensing applications, compared to their macro counterparts. Resonant sensors and actuators must reliably transduce signals and respond repeatably to external chemical and biological environments. The ability to tailor the surface properties with specific biomolecules can be used to create chemically functionalized NEMS oscillators for study of physical chemistry, biocompatibility, DNA hybridization and

Resonant nanoelectromechanical systems (NEMS) are being actively investigated as sensitive mass detectors for applications such as chemical and biological sensing. We demonstrate that highly uniform arrays of nanomechanical resonators can be used to detect the binding of individual DNA molecules through resonant frequency shifts resulting from the added mass of bound analyte. Localized binding sites created with gold nanodots create a calibrated response with sufficient sensitivity and accuracy to count small numbers of bound molecules. The amount of nonspecifically bound material from solution, a fundamental issue in any ultra-sensitive assay, was measured to be less than the mass of one DNA molecule, allowing us to detect a single 1587 bp DNA molecule.

We present a method for controlled deposition of oriented polymeric nanofibres. The method uses a microfabricated scanned tip as an electrospinning source. The tip is dipped in a polymer solution to gather a droplet as a source material. A voltage applied to the tip causes the formation of a Taylor cone, and at sufficiently high voltages, a polymer jet is extracted from the droplet. By moving the source relative to a surface, acting as a counter-electrode, oriented nanofibres can be deposited and integrated with microfabricated surface structures. For example, we deposited fibres of polyethylene oxide with diameters ranging from 100 to 1800 nm, with the diameter primarily depending on the concentration of the polymeric solution. In addition to the uniform fibre deposition, the scanning tip electrospinning source can produce self-assembled composite fibres of micro-and nanoparticles aligned in a polymeric fibre. We also deposited oriented conductive polymeric fibres of polyaniline and investigated the conductivity of these fibres as components for polymeric nanoelectronics.