Derived from the Greek word meaning ‘to squeeze’, piezoelectricity refers to the phenomenon where a solid material accumulates an electric charge following the application of pressure and, conversely, creates pressure when subjected to an electric field. First described by the French physicists Jacques and Pierre Curie, piezoelectric materials are widely used in modern electronics in the design of smart materials, and especially in the transformation of mechanical energy into an electronic signal. Common household items such as speakers, earphones and microphones invariably contain piezoelectric components, as do specialized equipment such as sonars, acoustic imaging devices and high-precision microbalances, as well as next-generation technologies such as piezoelectric memory devices and artificial skins and muscles.
However, piezoelectric materials typically used in device production do not inherently display piezoelectric capacity, and must be processed through costly and complex fabrication steps prior to use. Many of these materials are ceramics, which further suffer from high brittleness, low cyclic endurances, high processing temperatures and high production costs, and are composed of toxic elements that preclude their use in implantable sensors. Polymer-based piezoelectric materials avoid many of these issues and are an attractive alternative to ceramic-based piezoelectronics – and the research team of Dr. Bayindir has recently developed a particularly effective example.
Produced from poly(vinylidene floride) (PVDF), Bayindir group’s piezoelectric material was developed through a technique called iterative size reduction, a low-cost thermal drawing method that allows the fabrication of well-ordered nanofibers in prodigious lengths. Possessing the high piezoelectric capacity, thermal endurance and chemical resistance of ceramic piezoelectric materials with none of the drawbacks, the PVDF fibers are a strong candidate for the design of next-generation piezoelectronics. Using their polymeric material, the group has already designed a high-sensitivity tapping device and an energy-harvesting mechanism with enough power-generation capacity to run small devices such as pacemakers.
As PVDF is a biocompatible material, piezoelectric devices constructed with the polymer may be implanted within the human body to perform functions such as real-time heart rate monitoring, using energy created by natural motions – like that provided by the heartbeat. Bayindir group also has plans to develop a new device based on the arrangement of their polymer material into interdigitated electrodes in a fiber form. This device would be able to produce its own energy, communicate with the surrounding environment, record information such as temperature, pressure and sound, and respond to these signals as an artificial muscle.
Mehmet Kanik, one of the authors of the study, comments that the new
piezoelectric component has already made a significant impact in the scientific world: “Many researchers and companies around the world ask for samples or quotations for buying our piezoelectric fibers,” he says. In response to this interest, the group has also decided to patent the product and look into its commercial applications.
Mehmet Kanik explains the PVDF nanoribbons to Prof. Heinrich Rohrer.