Presentation Title: Nanogenerators and Nanopiezotronics

Abstract: Developing novel technologies for wireless nanodevices and nanosystems are of critical importance for in-situ, real-time and implantable biosensing, biomedical monitoring and biodetection. An implanted wireless biosensor 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. 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. We have demonstrated an innovative approach for converting nano-scale mechanical energy into electric energy by piezoelectric zinc oxide nanowire (NW) arrays. By deflecting the aligned NWs using a conductive atomic force microscopy (AFM) tip in contact mode, the energy that was first created by the deflection force and later converted into electricity by piezoelectric effect has been measured for demonstrating nano-scale power generator. The operation mechanism of the electric generator relies on the unique coupling of piezoelectric and semiconducting dual properties of ZnO as well as the elegant rectifying function of the Schottky barrier formed between the metal tip and the NW. Based on this mechanism, we have recently developed DC nanogenerator driven by ultrasonic wave in bio-fluid, which is a gigantic step towards applications in practice. This presentation will introduce the fundamental principle of nanogenerator and its potential applications. Finally, a new field is introduced on nano-piezotronics, which uses piezoelectric-semiconducting coupled property for fabricating novel and unique electronic devices and components.

[1] Z.L. Wang and J.H. Song "Piezoelectric Nanogenerators Based on Zinc Oxide Nanowire Arrays", Science, 312 (2006) 242-246.
[2] P.X. Gao, J.H. Song, J. Liu and Z.L. Wang "Nanowire Nanogenerators on Plastic Substrates as Flexible Power Source", Adv. Mater., 19 (2007) 67-72.
[3] X.D. Wang, J.H. Song J. Liu, and Z.L. Wang "Direct current nanogenerator driven by ultrasonic wave", Science, 316 (2007) 102-105.
[4] Z.L. Wang "Nano-piezotronics", Adv. Mater., 19 (2007) 889.
[5] Research supported by NSF, DARPA, NASA and Emory-Georgia Tech CCNE from NIH.
[6] more details at: http://www.nanoscience.gatech.edu/zlwang/

Biography: Dr. Zhong Lin (ZL) Wang is a Regents' Professor, COE Distinguished Professor and Director, Center for Nanostructure Characterization and Fabrication, at Georgia Tech. He has authored and co-authored four scientific reference and textbooks and over 500 peer reviewed journal articles, 55 review papers and book chapters, edited and co-edited 14 volumes of books on nanotechnology, and held 20 patents and provisional patents. Dr. Wang is the world's top 25 most cited authors in nanotechnology from 1992-2002 (ISI, Science Watch). His entire publications have been cited for over 19,000 times. The H-index of his publications is 67.

Dr. Wang discovered the nanobelt in 2001, which is considered to be a ground-breaking work. The paper on nanobelt was the second most cited paper in chemistry in 2001-2003 world-wide. His paper on piezoelectric nanosprings was one of the most cited papers in materials science in 2004 world-wide. His recent invention of world's first nanogenerator will have profound impacts to implantable biosensors and molecular machines/robotics. In 1999, he and his colleagues discovered the world's smallest balance, nanobalance, which was selected as the breakthrough in nanotechnology by the America Physical Society. He was elected to a fellow of American Physical Society in 2005, fellow of AAAS in 2006, has received the 2001 S.T. Li prize for Outstanding Contribution in Nanoscience and Nanotechnology, the 2000 and 2005 Georgia Tech Outstanding Faculty Research Author Awards, Sigma Xi 2005 sustain research awards, Sigma Xi 1998 and 2002 best paper awards, and the 1999 Burton Medal from Microscopy Society of America. Details can be found at: http://www.nanoscience.gatech.edu/zlwang.