Nano-Scale Energy Harvesters Show Large Scale Impact

nano-scale piezoelectric generator
Schematic view of typical Vertical nanowire Integrated Nanogenerator, (a) with full contact, and (b) with partial contact.

The production of nano-scale devices has drastically increased with the rise in technological applications, yet a major drawback to the functionality of nano-sized systems is the need for an equally small energy resource.

To address this need, Hamid Foruzande, Ali Hajnayeb and Amin Yaghootian from the Shahid Charmran University of Ahvaz in Iran have been modeling new piezoelectric energy harvester (PEH) technology at the nano-scale level. In their recent article, published this week in AIP Advances, from AIP Publishing, the team determined how small-scale dimensions impact nonlinear vibrations and PEH voltage harvesting.

Piezoelectric materials generate electricity from the application of mechanical stress, and are utilized in everything from cell phones to ultrasonic transducers. This electricity can also be generated by vibration-induced stresses, allowing scientists to create PEHs. These PEHs can be miniaturized down to a micro- or nanosize and used in conjunction with nano-scale devices.

“Nowadays, the need for new miniaturized wireless sensors is growing. These MEMS [Micro-Electro Mechanical Systems] or NEMS [Nano-Electro Mechanical Systems] sensors usually require a power source of their size,” Hajnayeb said.

Piezoelectric energy harvesting is a well-known process for converting energy available in an environment into energy that can power small electric devices. Traditionally, this has been used for generating a self-sufficient energy supply. Self-sufficiency is highly desirable for nano-scale devices due to the complicated nature of replacing small energy systems.

PEHs are gaining popularity for nano-scale applications due to their relatively simple structures, higher energy densities and ability to easily be scaled down. Macro-scale models have been extensively studied and provided a strong base point to produce nano-scale models. Foruzande, Hajnayeb and Yaghootian are taking advantage of these adaptable qualities and have generated nano-scale PEH models based on non-local elasticity theory.

“It’s necessary to use this theory for other systems at nano-scale and also the sensors in nano-scale, which use piezoelectric materials,” Hajnayeb said. “They have the same governing theory that we use in our article.”

The research team studied nonlinear vibrations and voltage based on nonlocal elasticity theory, which states that a point stress is dependent on the strain in a region around that point. Using this theory, they could derive nonlinear equations of motion with straightforward solutions. Their results showed that adding a nanobeam tip mass and increasing the scale factor would increase the generated voltage and vibration amplitude, hence increasing energy output.

Modeling micro- and nano-scaled PEHs was also able to reveal just what impact size effects had on the output they could expect. The researchers found that the error of neglecting size is significant when comparing macro and micro PEHs. Neglecting various size effects resulted in lower estimations of PEH vibrations.

Nano-scale sensor technology is becoming a hot commodity in the scientific industry due to its expansive applications. With applications in medicine, engineering, physics and more, nanotechnology has a lot to gain from the use of a stable energy source, such as these newly modeled PEHs.

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The article, “Nanoscale piezoelectric vibration energy harvester design,” is authored by Hamid Reza Foruzande, Ali Hajnayeb and Amin Yaghootian. The article appeared in AIP AdvancesSept. 26, 2017 (DOI: 10.1063/1.4994577) and can be accessed at http://aip.scitation.org/doi/full/10.1063/1.4994577.

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