(Press-News.org) Battery-powered devices could soon be a thing of the past thanks to a group of UK researchers who have created a novel energy harvester to power some of the latest wearable gadgets.
By strapping the energy harvester to the knee joint, a user could power body-monitoring devices such as heart rate monitors, pedometers and accelerometers by simply walking and not have the worry of running out of power and replacing batteries. Soldiers may find this device particularly useful as they often have to carry up to 10kg of power equipment when on foot patrol.
The device has been presented today, 15 June, in IOP Publishing's journal Smart Materials and Structures by researchers from Cranfield University, The University of Liverpool and University of Salford.
The energy harvesting device, which is designed to fit onto the outside of the knee, is circular and consists of an outer ring and central hub. The outer ring rotates as the knee joint goes through a walking motion. The outer ring is fitted with 72 plectra which "pluck" four energy-generating arms attached to the inner hub.
As an individual plectrum deflects off one of the arms – which are called bimorphs – it causes it to vibrate, much like a guitar string, and generates the electrical energy.
"A bimorph is a type of piezoelectric device capable of converting mechanical energy, such as the vibrating caused by the plectra, into electrical energy, and vice versa. Piezoelectric materials have long been used as sensors in SONAR and ultrasound scanners and have recently been the focus of attention in the field of energy harvesting," said lead author of the study Dr Michele Pozzi.
At the moment the device can harvest around two milliwatts of power but the researchers believe that with a few realistic improvements it could exceed 30 milliwatts of power, which could allow new generation GPS tracking, more advanced signal processing and more frequent and longer wireless transmission.
In this study, the energy harvester was tested on a knee motion simulator which reproduced the gait pattern of a human. The researchers were able to accurately control the simulator by examining the intricate detail in the movements of the knee joint by placing a selection of reflective markers on a human subject and using motion capture systems to monitor their walking pattern.
The subject was also fitted with three backpack loads to observe how the knee joint would move under a heavier load.
The knee itself is an ideal starting point for energy generation as it has a large change in angle during walking and does so at significant speeds. A device attached to the joint could therefore generate large amounts of power.
"There is an on-going project looking at manufacturing a more compact and truly wearable harvester. At the moment we are using precise but cost-effective manufacturing techniques for the plectra and casing and anticipate that remaining parts will be moulded industrially, slashing the cost. I'd put a cost tag of less than £10 for each harvester on a large scale production," continued Dr Pozzi.
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This study was initially funded by the EPSRC and DSTL as part of a joint project to reduce the heavy battery burden on dismounted soldiers.
From Friday 15 June, this paper can be downloaded from http://iopscience.iop.org/0964-1726/21/7/075023
Notes to Editors
Contact
1. For further information, a full draft of the journal paper or contact with one of the researchers, contact IOP Press Officer Michael Bishop:
Tel: 0117 930 1032
E-mail: Michael.Bishop@iop.org
The pizzicato knee-joint energy harvester: characterisation with biomechanical data and effect of backpack load
2. The published version of the paper "The pizzicato knee-joint energy harvester: characterisation with biomechanical data and effect of backpack load" Pozzi M et al 2012 Smart Mater. Struct. 7 075023 will be freely available online from Friday 15 June. It will be available at http://iopscience.iop.org/0964-1726/21/7/075023
Smart Materials and Structures
3. Smart Materials and Structures is a research journal dedicated to technical advances in smart materials, systems and structures, including materials, sensing and actuation, optics and electromagnetics, structures, control and information processing.
IOP Publishing
4. IOP Publishing provides publications through which leading-edge scientific research is distributed worldwide. IOP Publishing is central to the Institute of Physics (IOP), a not-for-profit society. Any financial surplus earned by IOP Publishing goes to support science through the activities of IOP. Beyond our traditional journals programme, we make high-value scientific information easily accessible through an ever-evolving portfolio of community websites, magazines, conference proceedings and a multitude of electronic services. Focused on making the most of new technologies, we're continually improving our electronic interfaces to make it easier for researchers to find exactly what they need, when they need it, in the format that suits them best. Go to http://ioppublishing.org/
The Institute of Physics
5. The Institute of Physics is a leading scientific society promoting physics and bringing physicists together for the benefit of all.
It has a worldwide membership of around 40 000 comprising physicists from all sectors, as well as those with an interest in physics. It works to advance physics research, application and education; and engages with policy makers and the public to develop awareness and understanding of physics. Its publishing company, IOP Publishing, is a world leader in professional scientific communications. Go to www.iop.org
END
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