(65aa) Carbon Nanotube Based Tunable Microbattery

Batteries are essential to the functioning of many modern technologies and have been the subject of much research, both in academia and industry. Much of this research has been devoted to decreasing the size and weight of the battery, while simultaneously increasing the energy density and current output. With increasing skill researchers are developing nanofabrication and microelectronics techniques. Some researchers have been turning their attention to using nanoscale patterns for use as electrodes. It is suggested that increased surface area would allow for increased reaction rate (due to larger reaction surface) and better battery performance would be achieved. The work for the first incarnation of the carbon nanotube (henceforth CNT) tunable microbattery project was inspired by work done by Madou and Wang of UC-Irvine (Biosensors and Bioelectronics, 2005), whose design was able to produce 78% more power than a comparable stack-plate battery. These results were possible through the application of a "bed of nails" design. The anodes and cathodes were in alternating rows by the use of an interdigitated array as charge collectors. It is believed that the vertically aligned carbon nanotube arrays grown by the Ready lab would be superior electrodes when compared to the amorphous carbon of the Madou and Wang design. The first semester of research on the tunable CNT based microbattery focused on the evolution of process flows for lab scale testing of the microbatteries. The main variables examined were the material of the interdigitated array, creation and comparison of several fabrication protocols as well as selection of the photoresist. Madou and Wang used a gold thin film in their work, but the Ready lab has experienced poor growth using such a thin film as a substrate in the past. TiN and TiW were chosen as alternative substrates. TiN was chosen for its good resistance values, while TiW was also chosen for its ease in fabrication. Three different fabrication protocols were developed for use; two using Microchem's SU8-2002 (negative) photoresist, and one using Microchem's S-1818 (positive) photoresist.