A novel 'flexo-electric' material that generates electricty upon compression has been developed. The material shows significant advantages over piezoelectric materials as it is non-toxic and generates a higher voltage at the nanoscale. It is hoped that the material will be used in self-charging pacemakers and ultra-sensitive sensors.
The new material has an inherent mechanical tension that causes the material to change shape upon the application of an electric voltage is applied. This behaviour also means that if the materials shape is changed by an external force electricity is generated. This flexo-electric effect increases as the material thickness decreases, meaning the thinner the material the greater the voltage generated.
This finding represents a completely new field of knowledge and has some promising applications, such as the recharging of pacemakers whilst in the human body. The novel material could also be used in the production of extremely sensitive sensors.
Crystalline materials that convert electric power into pressure and vice versa are called piezoelectric materials. These materials can be used in a number of electronic applications. However, the majority of piezoelectric materials contain lead. This has significantly held back the use of piezoelectric materials as lead is toxic tto both humans and the environment. Lead based materials also exhibit a lower piezoelectric effect decreases as the material is made thinner, which is the opposite of the new material.
The Thinner the Material, the Stronger the Effect
The existence of flexo-electric effects has been debated amongst physicists since 1960s. This is partly because the production methods that existed during the 1960s were not adequate for producing such materials.
The responsible research teams, from the University of Twente, Cornell University and the Catalan Institute of Nanotechnology, have now successfully developed a flexo-electric nanosystem with a thickness of 70 nm. Although the inherent flexo-electric effect of the material is weak, as the material is made thinner the effect becomes more pronounced.
The team are confident that flexo-electric materials with a thickness of just a few atomic layers can be created in future. Such ultra-thin materials could be used in a variety of applications.
You could make sensors that can detect a single molecule, for example. A molecule would land on a vibrating sensor, making it just fractionally heavier, slowing the vibration just slightly. The reduction in frequency could then easily be measured using the flexo-electric effect.
Professor Guus Rijnders - University of Twente
Apart from being used as ultra-sensitive sensors, these materials could be used in applications that only need small amounts of power, but are located in difficult to reach places like in cochlear implants or pacemakers in the human body.
The research has been published in the journal 'Nature Nanotechnology'