Winter 2006-2007 Schedule
Nanogenerators and Nano-Piezotronics
January 18, 2007; 3:00pm
Presented by:
Professor Zhong-Lin Wang
School of Materials Science and Engineering
Georgia Institute of Technology
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. 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.
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 principle, piezoelectric-field effect transistor, piezoelectric gated diode, sensors and resonators have been fabricated, which are the fundamental components of nano-piezotronics.
Electrochemical Energy Storage: Beyond the Horizon
January 26 , 2006; 3:00pm
Presented by:
Dr. Peter G. Bruce
School of Chemistry
University of St. Andrews, Scotland
Global warming and the diminishing availability of fossil fuels conspire to present the greatest threat to humanity in the 21st century. Many scientific, engineering and socio-economic approaches must be brought to bear in order to address this threat.
Whether for static or transportation applications, energy storage has a vital role to play in addressing global warming and preserving oil stocks. Rechargeable lithium batteries represent an attractive means of storing electrical energy because of their high energy density. However, to meet the challenge of energy storage for electric and hybrid vehicles or to balance the intermittent supply of energy from clean sources, such as wind, wave and solar, with consumer demand, new rechargeable lithium batteries, which are not simply an evolution of current technology, must be developed.
The presentation shall discuss some of the approaches being taken in our laboratory to synthesise, characterise and develop new positive and negative electrodes as well as new electrolytes that may lay the foundations for future generations of rechargeable lithium batteries. Nanostructured intercalation hosts for Li, based on nanotubes and mesoporous materials and capable of operating as lithium battery electrodes will be described, as will recent developments in crystalline polymer electrolytes. Conventionally ionic conduction in polymers was believed to occur only in the amorphous state above Tg, we have shown that this is not the case. A new class of conducting crystalline polymers will be presented.