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Organic electronic ratchets doing work
17 December 2010
Eindhoven University of Technology
Researchers at Eindhoven University of Technology (TU/e) and the COBRA research institute in Eindhoven have succeeded in causing electron transport using an electronic ‘ratchet’. This is the first time that usable powers have been generated at room temperature with a device of this kind. The finding opens the possibility of a new kind of wireless drive for microelectronic circuits.
An article about the research, which is led by dr.ir. Martijn Kemerink (TU/e Department of Applied Physics), is in the January 2011 edition of Nature Materials, with PhD student ir. Erik Roeling as first author. The article shows that in principle undirected electrical forces (caused by an alternating voltage) can cause a net movement of electrons in a single direction. Effectively this means that a direct current is generated by an alternating voltage.
This is the first time that usable voltages (sufficient to power a logic circuit, as the researchers have demonstrated) have been generated at room temperature with this kind of periodical, undirected force. Up to now very low temperatures have been required, and only a fraction of the power achieved by Roeling and Kemerink has been generated. The researchers used a modified organic field-effect transistor for their experiments, where electrodes are positioned asymmetrically below the channel of the transistor. Under the influence of the alternating voltage the electrons were able to make small steps in one direction, but not in the other – the same principle as a ratchet or pawl wheel. This movement of electrons is comparable to shaking marbles on a washboard – these also show a net movement in one direction. The effect is demonstrated in this video clip: http://www.youtube.com/watch?v=xExKoELgDXo
The researchers have included their finding in a logic circuit. In their test setup the ratchet was found to provide sufficient energy to power the circuit.
According to the researchers the finding is a first step on the way to a new method for wireless powering of microelectronic devices with a low energy consumption – for example identification tags, implanted ICs or sensors. However substantial further research will be needed before such applications can be realized.