Microfibre–nanowire hybrid structure for energy scavenging Kiarash Kiantaj 04/07/08 Yong Qin, Xudong Wang & Zhong Lin Wang /nature06601

Harvesting energy from environment Solar Thermal Mechanical (wind, friction, body movement or any environment disturbance) Foot steps Heartbeat Air flow Low frequency

piezoelectric zinc oxide nanowires Kevlar fibres coated with ZnO nanowires Hydrothermal growth TEOS (Tetraethoxysilane )

Characteristics Single crystalline nanowires hexagonal cross-section diameter in the range,50–200 nm length of 3.5 um Distance of few hundred nm

double-fibre model system as nanogenerator

300 nm gold layer Schottky barrier at Au-ZnO interface +V( reverse biased) -V (forward biased)

switching polarity testing Ri<250Mohm Two peaks 0.2 s delay

friction-induced electrostatic charges Only Au coated ZnO nanowire fibersOnly ZnO nanowire fibers

Frequency range: rpm

Improvements: Reducing the inner resistance of the fiber Deposition of a conductive layer directly onto the fiber reduction of inner resistance to 1 k-ohm surface contact area single yarn made of 6 fibers average current of 0.2 nA 30–50 times larger than single-fiber Series and parallel setup

Life time

Estimation of optimum output power density from textile fabrics:20–80mW per square meter

The end

“I-V characteristic of ZnO NW coated fiber measured using the circuit as presented at the right-hand side, where silver was used as the electrodes. The inner resistance of the 4 mm fiber used here is ~ 250 MΩ.”