Researchers have made significant strides in the development of functioning nanosystems. And leading the way in this area are Professor Zhong Lin Wang and his team at the Georgia Institute of Technology (Altanta). Using a nanogenerator technology, they have developed a nanosystem that is not only self-powered, but is also capable of wireless data transmission. Because of its ability to both record and transmit data without the need to ever change batteries, this discovery could someday benefit such medical devices as glucose meters, heartbeat monitors, and other biomedical applications.
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| Wang's team at Georgia Tech developed a nanostystem that can harvest and store mechanical or biochemical energy, and power a sensor, data processor, and data transmitter. |
There is a distinct need for nanodevice energy sources other than batteries, Wang notes, because devices and power sources are becoming increasingly smaller. As a result of this miniaturization, removal of the hard-to-find device in order to replace the battery presents a significant problem. "We started this research in 2005, and the goal was to build a self-powered nanosystem," Wang says. "At that time, this was a dream. We wanted to use energy power from biological sources, like muscle stretching, walking, breathing, or blood flow."
To make this dream a reality, the scientists required increasing output voltage and power to develop the nanogenerator. They began with a five-layer structure featuring a flexible polymer substrate in the middle, sandwiched by densely packed zinc-oxide (ZnO)-nanowire textured films. Electrodes were then placed on each outer surface.
Other piezoelectric materials were considered before ZnO was selected, Wang states. While lead-zirconate titanate (PZT) offered comparable performance to ZnO, it also involved extremely toxic lead. "We needed something biologically friendly," Wang explains. "With polyvinylidene fluoride (PVDF), performance was not as good. We had to balance the environmental concern with the ease and cost of making [the nanogenerator]."
Upon achieving this balance, the nanogenerator was able to power a nanodevice by 2009. The team then created a transmitter with minimal power consumption. Once all of these components had been developed, however, the challenge was to make everything work together. "Usually, we work on individual components," Wang says, "but this time, we had to work on the system."
Many improvements have been made since the nanosystem was first completed nearly a year ago, Wang adds. The transmitter range, for example, increased from one signal every 30 minutes to one every 10 seconds. Furthermore, the strain used to power the nanogenerator in the test environment was 1-3 Hz, similar to that of a human heartbeat. The next step for the nanosystem is to test it in vivo.
In addition to the nanogenerator, Wang's team has developed a device that converts biochemical energy, such as glucose, into electricity. It has also created a hybrid cell combining the biofuel cell and nanogenerator. "We are very collaborative to try to push this technology forward," Wang says. "From the progress we have made, in five years we'll use it in medical [applications]."
