The search for alternative energy sources is no longer restricted to just solar, wind and tidal energy. Nanogenerators have made it possible to convert ambient mechanical energy, such as vibrations and fluid flow, into a power source. Even human biological movement, such as muscle stretching, walking, heartbeat and blood flow, can be converted into useful energy via nanogenerators.
While this technology does present challenges associated with inconsistent frequencies and amplitudes of the movements, research is currently underway to overcome these difficulties. An alternating current (AC) generator was recently developed to draw energy from the cyclic stretching-releasing of a piezoelectric fine wire (PFW) and packaged on a flexible substrate. When the substrate undergoes bending, a potential drop is created in the PFW, leading to power generation.
Single wire generators (SWGs) are generally reported to demonstrate an efficient technology for harvesting energy from low-frequency vibrations. Essentially, because they are packageable and practical, they can be implanted in muscles, incorporated into cloth materials, and even used as part of shoe pads.
In this regard, a team from the Georgia Tech University has recently developed an SWG system that harvests energy from small-scale dynamic muscle movements, such as human finger tapping and the body movement of a hamster. A series of connections of four SWGs has been demonstrated to output an alternating voltage of approximately 0,1 to 0,5 V in amplitude.
The researchers constructed the SWG using a flexible polyimide film as the substrate and the two ends of the zinc oxide (ZnO) nanowire being fixed on the top surface of the substrate. The entire SWG system is reported to have been packaged with a flexible polymer so as to enhance robustness and adaptability.
The team began to experiment with the harvesting of energy from human finger movement. When the SWG was attached to the joint position of the index finger, the repeated bending of the finger resulted in a cycled strain in the nanowire. The deformation of the nanowire further produces a piezoelectric potential in the wire resulting in external electron flow and electrical power output.
A similar experiment was also conducted on a live hamster, using its regular and irregular motions such as running and scratching. The researchers report that a short-circuit current from a running hamster can reach about 0,5 nA, with an open-circuit voltage of about 50 to 100 mV.
Apart from having taken biomechanical energy conversion to a new level, the research team has also overcome the technical limitation to multiple integration of SWGs. The integration has helped increase the output voltage up to 0,1 to 0,5 V. Given their success with low-frequency biological vibration, it is foreseen that these SWGs could also be used to tap energy from other environmental disturbances.
For more information contact Patrick Cairns, Frost & Sullivan, +27 (0)21 680 3274, [email protected], www.frost.com
© Technews Publishing (Pty) Ltd | All Rights Reserved
printer friendly version