Electronic properties of nanoentities revealed by electrically driven rotation.

Direct electric measurement via small contacting pads on individual quasi-one-dimensional nanoentities, such as nanowires and carbon nanotubes, are usually required to access its electronic properties. We show in this work that 1D nanoentities in suspension can be driven to rotation by AC electric fields. The chirality of the resultantrotation unambiguously reveals whether the nanoentities are metal, semiconductor, or insulator due to the dependence of the Clausius-Mossotti factor on the material conductivity and frequency. This contactless method provides rapid and parallel identification of the electrical characteristics of 1D nanoentities.

Innovative mechanisms for precision assembly and actuation of arrays of nanowire oscillators.

Bottom-up assembling of Micro/Nano Electromechanical System (MEMS/NEMS) devices from nanoscale building blocks is highly desirable but extremely difficult to achieve. In this work, we report innovative mechanisms for precision assembly and actuation of arrays of nanowire NEMS devices that can synchronously oscillate between two designated positions for over 4000 cycles. The assembly and actuation mechanisms are based on unique magnetic interactions between nanoentities with perpendicular magnetic anisotropy (PMA) and electric-tweezer manipulation, our recent invention. Quantitative analysis of the dynamics of torques involved in the nano-oscillators reveals that the induced electrostatic torques due to the external electric fields between metallic NEMS components play a significant role in the mechanical actuation. These new findings are expected to inspire new in situ assembly and actuation strategies in the general field of NEMS devices such as nanomechanical switches for toggling on/off circuits and nanoresonators for biochemical sensors and radio frequency communication.

Subcellular-resolution delivery of a cytokine through precisely manipulated nanowires.

Precise delivery of molecular doses of biologically active chemicals to a pre-specified single cell among many, or a specific subcellular location, is still a largely unmet challenge hampering our understanding of cell biology. Overcoming this could allow unprecedented levels of cell manipulation and targeted intervention. Here, we show that gold nanowires conjugated with a cytokine such as tumour-necrosis factor-alpha can be transported along any prescribed trajectory or orientation using electrophoretic and dielectrophoretic forces to a specific location with subcellular resolution. The nanowire, 6 microm long and 300 nm in diameter, delivered the cytokine and activated canonical nuclear factor-kappaB signalling in a single cell. Combined computational modelling and experimentation indicated that cell stimulation was highly localized to the nanowire vicinity. This targeted delivery method has profound implications for controlling signalling events on the single cell level.