For example, the piezoelectricity in barium titanate can be increased by 300 percent when the material is reduced to a 2-nanometer-beam and pressure is applied. "Thus, you'll take an ordinary piezoelectric material and really give it some juice," he says.
Sharma underscores the flexoelectric effect is a function of size and the smaller the better, at least for generating piezoelectric power. Materials with nanoscale features such as nanoscale thin plates stacked on each other or materials with particles or holes the size of a few nanometers exhibit a much larger flexoelectric effect, he says.
Ramanan Krishnamoorti, chairman of the department of chemical and biomolecular engineering, is working with Sharma to embed classes of nanostructures in polymers to create unusual types of piezoelectrics.
Meanwhile, Sharma and professor Ken White recently reported that the electrical activity caused by flexoelectricity also affects a material's resiliency. They tested their theory that the elasticity of a material would be quite altered by flexoelectricity-caused electrical activity by poking the material with a sophisticated needle.
"We basically predicted that when you poke it, because of this electrical activity, depending upon how big a crater you create, your elastic behavior will change. It's not supposed to. Ordinarily, whether you make a big crater or small crater, if you calculate how stiff it is or soft it is, it'll give you the same answer a constant," Sharma says.
White and Sharma conducted several experiments on single crystals of materials.
"By monitoring the stiffness of the material as the crater became larger and larger," White says, "we discovered a change in elasticity relative to size, which could only be explained by flexoelectric effect."
Though a fair amount of research on piezoelectrics has been done, White says, the fabrication of piezoelectri
|Contact: Angela Hopp|
University of Houston