A definition of piezoelectricity – piezo being Greek for “subjected to pressure” - is the generation of the electrical polarisation of a material as a response to mechanical strain. This phenomenon is known as direct effect or generator effect and is applied fundamentally in the manufacture of sensors (mobile phone vibrators, lighters, etc.). In these cases piezoelectric materials, also used in actuators, undergo an inverse or motor effect, i.e. a mechanical deformation due to the application of an electrical signal.
Over the last four decades perovskita-type ceramics (zirconium or lead titanate ceramics) have been mainly used as piezoelectric materials in acoustic applications, amongst other reasons because of their high elastic modularity, their high dielectric constant and their low dielectric and elastic losses. However, and although they have also been used successfully in many other applications, ceramic piezoelectric materials have some important drawbacks: limited deformation, fragility and a high mass density that limit their use in sectors such as aeronautics or electrical-electronics. These limitations can be overcome in specific applications using polymeric piezoelectric materials instead of ceramic ones.The only piezoelectric polymer that currently exists on the market is Polyvinylidene Difluoride (PVDF). This semi-crystalline polymer is characterised by having very good piezoelectric properties, but only to 90 ºC. Thus the interest in synthesising new piezoelectric polymers capable of maintaining their properties at greater temperatures.
Patent applied for
At GAIKER-IK4 we have developed amorphous piezoelectric polymers to be employed in conditions of extreme temperature where semi-crystalline polymers cannot be used. To this end, and after prior work with different materials, the use of polymides was opted for, given their excellent thermal, mechanical and dielectric properties. Various dipolar groups (-CN, -SO2-, -CF3) have been incorporated into the molecule, varying the number and position of these groups in order to fix their physical - and consequently, their piezoelectric - properties. Moreover, it has been shown that the value for the temperature of vitreous transition is fundamental for these polymides, as this determines the temperature at which piezoelectric properties are lost. Specifically, this type of polymers show piezoelectric stability up to temperatures of 150ºC and do not begin to degrade until above 400 ºC.
We have been involved in this line of research at the Plastics and Composites Area for a number of years now and, particularly as a result of the research carried out jointly with the Department of Physical Chemistry at the University of the Basque Country (UPV/EHU), we have recently applied for a patent in the Oficina Española de Patentes y Marcas on “Polymides with piezoelectric properties”.
Irati Kortabitarte | alfa
One in 5 materials chemistry papers may be wrong, study suggests
15.12.2017 | Georgia Institute of Technology
Scientists channel graphene to understand filtration and ion transport into cells
11.12.2017 | National Institute of Standards and Technology (NIST)
DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.
Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
15.12.2017 | Power and Electrical Engineering
15.12.2017 | Materials Sciences
15.12.2017 | Life Sciences