Shear Modulus Property Characterization of Nanorods

We demonstrate an innovative technique for the direct measurement on the shear modulus of an individual nanorod. This measurement is based on atomic force microscopy (AFM) and microfabrication techniques. A nanorod is first aligned along the edge of a small trench in a silicon substrate, and then one end of the nanorod is fixed on the substrate. When an AFM tip scans over the nanorod in contact mode, the nanorod will be twisted by the comprehensive action from the force of the AFM tip, confinement from the trench edge and the fixing end. The shear deformation and the corresponding force that caused the deformation can be retrieved from topography and lateral force image, respectively. By small-angle approximation, the shear modulus of the ZnO NR, which has a radius of 166 nm and a length of 4 μm, is measured to be 8.1 ± 1.9 GPa. This method can be applied directly to characterize the shear modulus of any nanowire/nanorod that possesses a polygon cross section

Paper/Carbon Nanotube-Based Wearable Pressure Sensor for Physiological Signal Acquisition and Soft Robotic Skin

A wearable and flexible pressure sensor is essential to the realization of personalized medicine through continuously monitoring an individual’s state of health and also the development of a highly intelligent robot. A flexible, wearable pressure sensor is fabricated based on novel single-wall carbon nanotube /tissue paper through a low-cost and scalable approach. The flexible, wearable sensor showed superior performance with concurrence of several merits, including high sensitivity for a broad pressure range and an ultralow energy consumption level of 10^–6 W. Benefited from the excellent performance and the ultraconformal contact of the sensor with an uneven surface, vital human physiological signals (such as radial arterial pulse and muscle activity at various positions) can be monitored in real time and in situ. In addition, the pressure sensors could also be integrated onto robots as the artificial skin that could sense the force/pressure and also the distribution of force/pressure on the artificial skin

Catalyst-Free, Selective Growth of ZnO Nanowires on SiO₂ by Chemical Vapor Deposition for Transfer-Free Fabrication of UV Photodetectors

Catalyst-free, selective growth of ZnO nanowires directly on the commonly used dielectric SiO₂ layer is of both scientific significance and application importance, yet it is still a challenge. Here, we report a facile method to grow single-crystal ZnO nanowires on a large scale directly on SiO₂/Si substrate through vapor–solid mechanism without using any predeposited metal catalyst or seed layer. We found that a rough SiO₂/Si substrate surface created by the reactive ion etching is critical for ZnO growth without using catalyst. ZnO nanowire array exclusively grows in area etched by the reactive ion etching method. The advantages of this method include facile and safe roughness-assisted catalyst-free growth of ZnO nanowires on SiO₂/Si substrate and the subsequent transfer-free fabrication of electronic or optoelectronic devices. The ZnO nanowire UV photodetector fabricated by a transfer-free process presented high performance in responsivity, quantum efficiency and response speed, even without any post-treatments. The strategy shown here would greatly reduce the complexity in nanodevice fabrication and give an impetus to the application of ZnO nanowires in nanoelectronics and optoelectronics