Microfibre–nanowire hybrid structure for energy scavenging

[OKIsItJustMe]

http://www.nature.com/nature/journal/v451/n7180/full/nature06601.html

Nature 451, 809-813 (14 February 2008) | doi:10.1038/nature06601; Received 10 October 2007; Accepted 13 December 2007

Microfibre–nanowire hybrid structure for energy scavenging

Yong Qin^1,2, Xudong Wang^1,2 & Zhong Lin Wang<sup>1

1</sup>. School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, USA
². These authors contributed equally to this work.

Correspondence to: Zhong Lin Wang1 Correspondence and requests for materials should be addressed to Z.L.W. (Email: [e-mail]).

Abstract

A self-powering nanosystem that harvests its operating energy from the environment is an attractive proposition for sensing, personal electronics and defence technologies¹. This is in principle feasible for nanodevices owing to their extremely low power consumption^{2, 3, 4, 5}. Solar, thermal and mechanical (wind, friction, body movement) energies are common and may be scavenged from the environment, but the type of energy source to be chosen has to be decided on the basis of specific applications. Military sensing/surveillance node placement, for example, may involve difficult-to-reach locations, may need to be hidden, and may be in environments that are dusty, rainy, dark and/or in deep forest. In a moving vehicle or aeroplane, harvesting energy from a rotating tyre or wind blowing on the body is a possible choice to power wireless devices implanted in the surface of the vehicle. Nanowire nanogenerators built on hard substrates were demonstrated for harvesting local mechanical energy produced by high-frequency ultrasonic waves^{6, 7}. To harvest the energy from vibration or disturbance originating from footsteps, heartbeats, ambient noise and air flow, it is important to explore innovative technologies that work at low frequencies (such as <10 Hz) and that are based on flexible soft materials. Here we present a simple, low-cost approach that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres. By entangling two fibres and brushing the nanowires rooted on them with respect to each other, mechanical energy is converted into electricity owing to a coupled piezoelectric–semiconductor process^{8, 9}. This work establishes a methodology for scavenging light-wind energy and body-movement energy using fabrics.

The fibres used in our experiments were Kevlar 129 fibres, which have high strength, modulus, toughness and thermal stability. ZnO nanowires were then grown radially on the fibre surface using a hydrothermal approach¹⁰. A typical scanning electron microscopy (SEM) image of a Kevlar fibre covered by ZnO nanowires is shown in Fig. 1a. Along the entire length of the fibre, ZnO nanowires grew radially and exhibited a very uniform coverage and well preserved cylindrical shape. Some splits in the nanowire arrays can be identified (Fig. 1b), which were produced owing to the growth-induced surface tension in the seeding layer. All of the ZnO nanowires are single crystalline, and have a hexagonal cross-section with a diameter in the range approx50–200 nm and a typical length of approx3.5 mum. Their top and side surfaces are smooth and clean, indicating that they are able to form the reliable metal–semiconductor junctions needed for the nanowire nanogenerators. The space between the nanowires is of the order of a few hundred nanometres, which is large enough for them to be bent to generate the piezoelectric potential¹¹. The nanowires' tips are separated from each other owing to their small tilting angles (<±10°), but their bottom ends are tightly connected (Fig. 1b inset). As a result, a continuous ZnO film at the nanowires' roots served as a common electrode for signal output. Previous experiments showed that AFM (atomic force microscope) manipulation of a solution-grown ZnO nanowire can give up to 45 mV output voltage¹².

...

http://news.bbc.co.uk/2/hi/technology/7241040.stm

Nanowires allow 'power dressing'

By Jonathan Fildes
Science and technology reporter, BBC News



"Power dressing" may soon have a very different and literal meaning.

Scientists in the US have developed novel brush-like fibres that generate electrical energy from movement.

Weaving them into a material could allow designers to create "smart" clothes which harness body movement to power portable electronic gadgets.

Writing in the journal Nature, the team say that the materials could also be used in tents or other structures to harness wind energy.

"Our goal is to make self-powered nanotechnology," Professor Zhong Lin Wang of the Georgia Institute of Technology and one of the authors of the paper told BBC News.

...



...

[thunder rising]

1. More Nano-Vapor-Ware (or wear .. whatever)? Hell we don't even tap ocean tidal power.

[OKIsItJustMe]

2. There is no silver bullet

Advances are happening in tidal power:
http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=133051&mesg_id=133051
http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=130340&mesg_id=130348

We need more than one way to generate clean electricity.

[eppur_se_muova]

3. Robot glider harvests ocean heat (BBC)

By Jonathan Fildes
Science and technology reporter, BBC News

A sea-going robotic glider that harvests heat energy from the ocean has been tested by US scientists.

The yellow, torpedo-shaped machine has been combing the depths of seas around the Caribbean since December 2007.

The team which developed the autonomous vehicle say it has covered "thousands of kilometres" during the tests.

The team believe the glider - which needs no batteries - could undertake oceanographic surveys for up to six months at a time.

"We are tapping a virtually unlimited energy source for propulsion," said Dave Fratantoni of the Wood's Hole Oceanographic Institute (WHOi).
***
more: http://news.bbc.co.uk/2/hi/technology/7234544.stm

ON EDIT: Oopers, meant to start a new thread in Science, not respond to OP.

[thunder rising]

4. What a deal only $10M/mi!!!