Quality factors as high as 207 000 are demonstrated at room temperature for radio-frequency silicon nitride string resonators with cross sectional dimensions on the scale of 100nm, made with a nonlithographic technique. A product of quality factor and surface to volume ratio greater than 6000nm−1 is presented, the highest yet reported. Doubly clamped nanostring resonators are fabricated in high tensile-stress silicon nitride using a nonlithographic electrospinning process. We fabricate devices with an electron beam process, and demonstrate frequency and quality factor results identical to those obtained with the nonlithographic technique. We also compare high tensile-stress doubly clamped beams with doubly clamped and cantilever resonators made of a lower stress material, as well as cantilever beams made of the high stress material. In all cases, the doubly clamped high stress beams have the highest quality factors. We therefore attribute the high quality factors to high tensile stress. Potential dominant loss mechanisms are discussed, including surface and clamping losses, and thermoelastic dissipation. Some practical advantages offered by these nanostrings for mass sensing are discussed.

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Fibers seen in a new light? Inorganic–organic heterostructured cylindrical waveguides are prepared by a one‐step electrospinning approach, where the photoluminescence from semiconductor quantum dots embedded in a fiber acts as an internal light source. Subwavelength‐sized nanofibers (see image) with a length of several micrometers act as waveguides. Integrating such structures with Si‐based microelectronics to realize nanoscale optoelectronics is envisaged.

We demonstrate the operation of radio frequency nanoscale flexural resonators in air and liquid. Doubly clamped string, as well as singly clamped cantilever resonators, with nanoscale cross-sectional dimensions and resonant frequencies as high as 145 MHz are driven in air as well as liquid with an amplitude modulated laser. We show that this laser drive technique can impart sufficient energy to a nanoscale resonator to overcome the strong viscous damping present in these media, resulting in a mechanical resonance that can be measured by optical interference techniques. Resonance in air, isopropyl alcohol, acetone, water, and phosphate-buffered saline is demonstrated for devices having cross-sectional dimensions close to 100 nm. For operation in air, quality factors as high as 400 at 145 MHz are demonstrated. In liquid, quality factors ranging from 3 to 10 and frequencies ranging from 20 to 100 MHz are observed. These devices, and an all-optical actuation and detection system, may provide insight into the physics of the interaction of nanoscale mechanical structures with their environments, greatly extending the viscosity range over which such small flexural resonant devices can be operated.

We have used scanned electrospinning to deposit oriented polyethylene oxide and silica glass fibres over trenches etched in silicon. We measured the Young’s moduli of the fibres using an atomic force microscope. The Young’s moduli of the glass fibres agree with values calculated from previously measured mechanical resonance frequencies of similar fibres. The Young’s moduli of the polyethylene oxide fibres are significantly larger than those reported for polyethylene oxide bulk and films, suggesting molecular orientation in the fibres.

3D microfluidic networks are fabricated in a gelatin hydrogel using sacrificial melt-spun microfibers made from a material with pH-dependent solubility. The fibers, after being embedded within the gel, can be removed by changing the gel pH to induce dissolution. This process is performed in an entirely aqueous environment, avoiding extreme temperatures, low pressures, and toxic organic solvents.

We report on the structure-thermal transport property relation of individual polyethylene nanofibers fabricated by electrospinning with different deposition parameters. Measurement results show that the nanofiber thermal conductivity depends on the electric field used in the electrospinning process, with a general trend of higher thermal conductivity for fibers prepared with stronger electric field. Nanofibers produced at a 45 kV electrospinning voltage and a 150 mm needle-collector distance could have a thermal conductivity of up to 9.3 W m(-1) K(-1), over 20 times higher than the typical bulk value. Micro-Raman characterization suggests that the enhanced thermal conductivity is due to the highly oriented polymer chains and enhanced crystallinity in the electrospun nanofibers.