Feb 6, 2013
Structural monitoring added to application list for nanogenerators
The measurement of vibration frequencies is important for structural monitoring, damage detection, security systems and the prediction of natural disasters, to name just a few areas of interest. Cantilever beam-based sensors are often deployed, where the vibration spectrum of the cantilever is detected directly by a laser beam. To be compatible with smart/intelligent material systems and structures, the sensors should be small, flexible and lightweight. In addition, for locations that are hard to reach or sites that are difficult to access, the sensors should be self-powered and self-sensing.
Nanogenerators (NGs) based on piezoelectric nanowires (NWs) have been developed as a key technology for converting ambient mechanical energy into electricity. In fact, researchers have shown that ZnO NWs can successfully convert external mechanical energy, biomechanical energy, thermal energy and magnetic energy into electricity. Developers have used NGs to build self-powered nanosystems such as ultraviolet (UV) sensors, wireless data transmission and Hg2+ ion sensors.
Direct measure of vibration
Now a team led by Zhong Lin Wang at the Beijing Institute of Nanoenergy and Nanosystems has shown that NGs can be used as an active sensor for detecting vibration. In the study, Wang and Aifang Yu, a postdoctoral fellow in the group, demonstrated a flexible, compact and lightweight NG as an active sensor for detecting the vibration spectrum of a drum membrane without the use of an external power source.
The output current/voltage signal of the NG provides a direct measure of the strain of the local vibrating drum membrane and contains rich detail, notably the vibration frequency, vibration speed and vibration amplitude.
In testing, data from the self-powered, low-cost vibration sensors was compared with laser vibrometer readings, which showed that the NG-based devices were capable of detecting the local vibration frequency of the drum membrane accurately.
A spatial arrangement of NGs on the membrane can deliver position-dependent vibration information of the surface. The measured frequency spectrum can be understood based on theoretically calculated vibration modes. This work further expands the application of NGs.
Full details can be found in the journal Nanotechnology.
About the author
Dr Zhong Lin (ZL) Wang received his PhD from Arizona State University in transmission electron microscopy. He now is the Hightower Chair in Materials Science and Engineering, Regents' Professor at Georgia Tech, and Director of the Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Science. For more information, visit www.nanoscience.gatech.edu.