Professor Guus Rijnders, pictured, from the University of Twente believes it will be possible to create flexoelectric materials with a thickness of just a few atomic layers. “You could make sensors that can detect a single molecule, for example,” he said. “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.” In addition to ultra sensitive sensors, flexoelectric materials could also be useful in applications that require a limited amount of power, such as pacemakers and cochlear implants.
Like piezoelectric materials, flexoelectric devices can either generate electricity when deformed or change their shape when a voltage is applied. However, while the piezoelectric effect decreases with thickness, the team claims the thinner the material, the stronger the flexoelectric effect becomes.
Another difference is that, while piezoelectricity is hard to demonstrate in silicon, the flexoelectric effect can be exhibited by any dielectric material. Flexoelectricity is also said to be more linear and temperature independent than the piezoelectricity of a ferroelectric.
According to the researchers, the desirable attributes of flexoelectricity are maintained at the nanoscale, while the figure of merit – bending curvature divided by the applied electric field – of the first prototype is comparable to state of the art piezoelectric bimorph cantilevers.
The team also believes that all high-k dielectric materials used currently in transistor technology should also be flexoelectric, thus providing a route to integrating ‘intelligent’ electromechanical functionalities within current transistor technology.
