Scientists develop bespoke piezoelectric material

Atlanta, US- Researchers at the Georgia Institute of Technology have developed a manufacturing process to form piezoelectrically active nanostructures from lead zirconate titanate (PZT).

Named the “soft template infiltration technique”, the process could enable fabrication of ferroelectric nanostructures with user-defined shapes, location and pattern variations.

This could ultimately lead to production of actively-tunable photonic and phononic crystals, terahertz emitters, energy harvesters, micromotors, micropumps and nanoelectromechanical sensors, actuators and transducers.

“These are truly smart materials, which means they respond to external stimuli such as applied electric fields, thermal fields or stress fields,” said Nazanin Bassiri-Gharb, an assistant professor at Georgia Tech.

For example, the piezoelectric effect could permit fabrication of “nano-muscle” tubes that would act as tiny pumps when an electric field is applied to them. The fields could also be used to tune the properties of photonic crystals, or to create structures whose size can be altered slightly to absorb electromagnetic energy.

In fabricating the nanotubes, the researchers began with a silicon substrate and spin-coated a negative electron-beam resist material onto it. A template was created using electron-beam lithography, and a thin layer of aluminum oxide was added on top of that using atomic layer deposition.

The template was then immersed under vacuum into an ultrasound bath containing a chemical precursor solution for PZT. The structures were pyrolyzed, then annealed in a two-step heat treating process to crystallise the material and decompose the polymer substrate.

The process produced free-standing PZT nanotubes connected by a thin layer of the original aluminum oxide.

“One of our most important observations is that these piezoelectric nanomaterials allow us to generate a factor of four to six increase in the extrinsic piezoelectric response compared to the use of thin films,” said Baassiri-Gharb.

“This would be a huge advantage in terms of manufacturing because it means we could get the same response from much smaller structures than we would have had to otherwise use.”