Nano-generators have big uses

Within three to five years, the research team led by Wang Zhonglin, a professor of materials science and engineering at the Georgia Institute of Technology, said that after five years of research and development, the nano-generators they manufacture can provide power to traditional small electronic devices. , Light up a small liquid crystal display (LCD). According to the American Physicist Organization Network, this nanogenerator uses a fine array of nanowires to collect mechanical energy from the surrounding environment, which is then converted into electrical energy to provide power to electronic devices.

In addition, Wang Zhonglin and colleagues recently made a series of other advancements in the field of nanogenerators, including the simpler nanogenerator construction technology published in last week's online edition of Nano Express, and the earlier publication. Research results on Nano Express and Nature Communications.

Wang Zhonglin said that although currents generated by nanogenerators are lower than those required by devices such as iPods or pacemakers, nanogenerators can charge iPods or pacemakers within three to five years.

The Enhanced Output Power Nanogenerator Project was funded by the US Department of Defense Advanced Research Projects Agency (DARPA), the United States Air Force, and the National Science Foundation. In early 2006, Wang Zhonglin published a paper in the United States "Science" that states that nanowires synthesized from piezoelectric materials can convert mechanical energy into electrical energy, and for the first time proposed the principle of nanogenerators.

Wang Zhonglin's nanogenerators rely mainly on piezoelectric effects such as those found in crystalline materials such as zinc oxide. Piezoelectric effect refers to the potential of a crystalline material to produce a potential under mechanical pressure. By capturing and collecting the charge generated by the zinc oxide nanowires, a voltage of 3 volts, approximately 300 nanoamps, can be generated.

In the latest experiment, the mechanical energy comes from the researchers' pressing action on a nanogenerator located between two fingers. In other cases, mechanical energy may also come from the heartbeat, the weight of the hiker's shoes on the road, the rustling of the clothes under the wind blowing, and so on.

Wang Zhonglin stated that by simplifying the design and making the equipment more stable, and combining the power generated by more nanowires, they succeeded in increasing the power generated by the nanowires enough to drive liquid crystal displays, lasers, light-emitting diodes and other electronic devices.

In another paper published in the "Nanjing Express", Wang Zhonglin and other colleagues reported on another research progress in improving the output power of nanogenerators. Their method involves two steps: first transfer the vertical zinc oxide nanowires to a polymer receiving substrate to form a horizontal array of nanowires, and then connect all nanowires together with parallel strip electrodes. Using a single-layered structure, the researchers generated an open circuit voltage of 2.03 volts and achieved a maximum output energy density of about 11 milliwatts per cubic centimeter.

Wang Zhonglin said that compared to current power generation equipment, nano-generators have many advantages. They do not require toxic heavy metals like many piezoelectric materials, which makes them very environmentally friendly and does not harm human health when embedded in the human body. They can also be made at temperatures below the boiling point of water, ie below the temperatures required for the manufacture of standard electronic components. In addition, such generators “are likely to be mass-produced” so that they can “fly into the homes of ordinary people” and apply them to all aspects of life.

Wang Zhonglin pointed out that since the beginning of the research on nano-generators in 2005, the output power of nano-generators has been greatly improved, and the current intensity of nano-generators has increased by 100 times compared with that of a year ago. If the technology is continually improved, within three to five years, nano-generators can be truly applied to health care equipment, personal electronics and environmental monitoring equipment.

Simplified assembly technology The earliest zinc oxide nanogenerators used a nanoarray fixed to a rigid substrate with a metal electrode attached to the top of the nanoarray; later nanogenerators embedded both ends of the nanowire in a polymer. Power is generated by simply bending the nanowires. Regardless of their circuit layout, building such a nanogenerator not only requires careful "planting" of nanowires, but also requires laborious assembly work.

In the latest paper, Wang Zhonglin's team reported a simpler assembly technique. First, they planted a new class of nanowire arrays, cut the conical nanowires from the substrate, put them in ethanol solution, and then dropped the nanowire solution onto a tiny metal. Electrode and a piece of soft polymer film. After the ethanol evaporates, a new nanowire/polymer layer emerges. Finally, a large number of nanowire/polymer layers are used to build a composite material. Wang Zhonglin believes that this process can produce large-scale production of nano-generators.

The resulting nanogenerator is about 2 cm by 1.5 cm in size, and when it is bent, the generated electricity is sufficient to light up the display on a pocket calculator.

PZT manufactures nanowires In another paper published in Nature-Communications Online, Wang Zhonglin and colleagues report a new method using lead zirconate titanate (PZT) to assemble piezoelectric nanowires. PZT is a polycrystal obtained by sintering lead dioxide, lead zirconate, and lead titanate at a high temperature of 1,200 degrees Celsius.

The research team reported the first vertical PZT single crystal nanowire array that can grow on chemical films on conductive and non-conductive substrates. During the demonstration, the PZT nanogenerator provided power for a laser diode by using a rectifier circuit to convert AC power to DC power, which indicates that the PZT can also be a component of the nanogenerator.

Wang Zhonglin said that although PZT does not perform as well as zinc oxide in power generation, this alternative material allows researchers to flexibly select the best materials according to their needs.