ACerS member Zhong-Lin Wang continues to make interesting progress on developing nanowire power generators and other energy-scavenging devices, and recently has demonstrated a nanogenerator that can be powered by the motion of a beating heart or the flexing of diaphragms and lungs.
When I last wrote about Wang in early 2009, he was demonstrating a “flex charge pump” generator constructed of zinc-oxide piezoelectric fine wires that measure three to five microns in diameter and 200 to 300 microns in length. Back then, he was thinking these tiny generators could be used in self-powered wireless sensing systems that gather, store and transmit data. He imagined then that his method could be scaled down to a nano size.
Since that time, however, it appears that Wang, a professor at Georgia Tech, has also become more interested in applications involving biomedical sensors. In fact, in a paper published in Advanced Materials, he and his fellow researchers report on what may be the first in vivo testing of nanoscale power generators activated by the breathing and heart beat of a rat. This could be a significant step forward in the creation of self-powered implanted nanodevices that could, for example, monitor blood pressure or blood glucose levels. (It should be noted that a group of Cleveland-area researchers reported in July 2009 on a larger-scale in vivo generator activated by a rabbit’s quadriceps).
Wang and his team sealed zinc-oxide nanowires in a polymer. The polymer served as a shield to the rat’s body fluids and to be a barrier to outside electrical sources. They then glued the 2 mm x 5 mm rectangular unit to the rat’s diaphragm muscle. The breathing motion generated 4 picoamps of current at a potential of 2 millivolts. Even more power was generated when the unit was glued to the rat’s heart: 30 picoamps at 3 millivolts.
Wang acknowledges that, while significant, this new work is more of a interim step than a final achievement, and that much more power is going to be needed for actual sensors. But Wang notes that his group has also figured out how to integrate a large number of nanowire energy harvesters into a single 4 mm2 power source (a vertically integrated nanogenerator, or VING) and has demonstrated the feasibility with a self-powered nanowire pH sensor and a nanowire UV sensor.
Interestingly, Wang has also demonstrated a hybrid generation system that could be used in vivo. This system, used to power a UV sensor combines a piezo nanogenerator with a biofuel cell that scavenges biochemical energy (glucose/O2).
Apparently the next step if to do in vivo testing of a VING–sensor system.
He is another video featuring an interview with Wang from about a year ago