Piezoelectric Nanogenerators for Wireless Nanosensors

Developing novel technologies for wireless nanodevices and nanosystems are of critical importance for in-situ, real-time and implantable biosensing, biomedical monitoring and biodetection. Nanosensors are currently under intense development for ultrasensitive and real-time detection of biomolecules. An implanted wireless biosensor, for example, requires a power source, which may be provided directly or indirectly by charging of a battery. It is highly desired for wireless devices and even required for implanted biomedical devices to be self-powered without using battery.

So far, innovations for delivering nanoscale power source are almost non-existent; while huge emergent needs for nanoscale sensing devices continue for biological sensing and defense applications. Therefore, it is essential to explore innovative nanotechnologies for converting mechanical energy (such as body movement, muscle stretching), vibration energy (such as acoustic/ultrasonic wave), and hydraulic energy (such as body fluid and blood flow) into electric energy that will be used to power nanodevices without using battery. It also has a huge impact to miniaturizing the size of the integrated nanosystems by reducing the size of the power generator and improving its efficiency and power density. Once this is truly feasible, we have made the nanosystems.

In a report published recently in Science [1] we demonstrate the first work or achieving nano-scale energy conversion by nanotechnology. This is also the first example that shows the coupling of piezoelectric and semiconducting properties is the key for the piezoelectric discharge process. ZnO is a unique material for this study. The principle and technology demonstrated here have the potential of converting mechanical movement energy (such as body movement, muscle stretching, blood pressure), vibration energy (such as acoustic/ultrasonic wave), and hydraulic energy (such as flow of body fluid, blood flow, contraction of blood vessel) into electric energy that may be sufficient for self-powering nanodevices and nanosystems. The nano-generator could be the foundation for exploring new self-powering technology for in-situ, real-time and implantable biosensing, biomedical monitoring and biodetection, with great potential for defense and civil applications.

Figure Piezoelectric nanogenerators based on aligned ZnO nanowires. (A) Scanning electron microscopy images of as-grown ZnO nanowires on sapphire substrate. (B) Schematic experimental procedure for generating electricity from a nanowire using a conductive atomic force microscope (AFM). (C) Piezoelectric discharge voltage measured at an external resistor when the AFM tip scanned across the nanowire arrays.

The difficulty that we have to overcome was the understanding of the piezoelectric discharge process and its experimental proof. We did a series of experiments to verify that the observed phenomenon is truly caused by piezoelectric discharge.

The principle and technology demonstrated here have the potential of converting mechanical movement energy (such as body movement, muscle stretching, blood pressure), vibration energy (such as acoustic/ultrasonic wave), and hydraulic energy (such as flow of body fluid, blood flow, contraction of blood vessel) into electric energy that may be sufficient for self-powering nanodevices and nanosystems.

The nano-generator could be the foundation for exploring new self-powering technology for in-situ, real-time and implantable biosensing, biomedical monitoring and biodetection, with great potential for defense and civil applications.
The technology can also be applied for building wireless, self-powered sensors by harvesting energy from the environment.
The technology can also be used to generate electricity by body movement.

The objective of the follow up work is:
To develop a unique technology capable of converting mechanical movement energy (such as body movement, muscle stretching, blood pressure), vibration energy (such as acoustic/ultrasonic wave), and hydraulic energy (such as flow of body fluid, blood flow, contraction of blood vessel, dynamic fluid in nature) into electric energy that is sufficient for self-powering nanodevices and nanosystems in biological systems; and

To fabricate large-power output electric generator using nanomaterials, which can be grown on substrates such as metal foils, flexible organic plastic substrates, ceramic substrates and compound semiconductors, aiming at achieving flexible power source for biomedical, defense and civil applications.

[1] Zhong Lin Wang* and Jinhui Song ^“Piezoelectric Nanogenerators Based on Zinc Oxide
Nanowire Arrays”, Science, 312 (2006) 242-246.