New battery implantable for human-powered devices?
According to foreign media reports, scientists are currently studying the conversion of mechanical, thermal, and chemical energy in the human body into electrical energy through piezoelectric effects, thermal energy conversion, electrostatic effects, and chemical reactions, so as to provide wearable or implantable devices. powered by.
In ISing the Body Electric, poet Walt Whitman speaks fondly of the "action and power" of "beautiful, strange, breathing, laughing muscles." More than 150 years later, MIT materials scientist and engineer Canan Dagdeviren and her colleagues are using research to give new meaning to Whitman's poetry. They are working on a device that can generate electricity from the beating of people's hearts.
Today's electronics are so powerful that the computing power of smartphones far exceeds the processing power of NASA's associated crew equipment when the first astronauts were sent to the moon in 1969. Over time, the rapid development of technology has led to higher and higher expectations for wearable or implantable devices.
The main drawback of most wearable and implantable devices is still battery life, whose limited battery capacity can limit the long-term use of the device. When the pacemaker's power runs out, all you need to do is replace the battery for the patient's surgery. The fundamental solution to this problem may lie within the human body, which is rich in chemical, thermal, and mechanical energy. This has led scientists to repeatedly study how the device harvests energy from the human body.
For example, the movement a person makes while breathing can generate 0.83 watts of energy; the human body has about 4.8 watts of heat in a calm state; and a person's arms can generate up to 60 watts of energy when exercising. A pacemaker needs only five millionths of a watt to run for seven years, a hearing aid needs only one thousandth of a watt to run for five days, and a watt of power can power a smartphone for five Hour.
Now Dagviren and colleagues are investigating how to use the human body itself as a source of energy for the device. Researchers have already started testing the wearable or implantable device in animals and humans.
One of these energy harvesting strategies involves converting energy from vibration, pressure and other mechanical stresses into electrical energy. This method produces so-called piezoelectricity, which is commonly used in speakers and microphones.
A commonly used piezoelectric material is lead titanate zirconate, but its high lead content has raised concerns because lead is too toxic to humans. "But to break down the lead structurally, you need to heat it to more than 700 degrees Celsius," Dagvilen said. "You'll never get to that temperature in the human body."
To take advantage of the piezoelectric effect, Dagviren and her colleagues developed flat devices that can be attached to organs and muscles such as the heart, lungs and diaphragm. These devices are "mechanically invisible" because their mechanical properties are more similar to their environment, so they move without interfering with the normal functioning of these tissues.
So far, the devices have been tested on cows, sheep and pigs, because these animals have hearts about the same size as a human heart. "When these devices are mechanically distorted, they generate positive and negative charges, voltages and currents, so that energy can be harvested to charge the battery," Dagviren explained. "You can use them to run the heart biomedical devices such as pacemakers, rather than having to be surgically replaced every six or seven years after the battery is depleted.”
Scientists are also developing wearable piezoelectric energy harvesters that can be worn on the knee or elbow, or placed in shoes, pants or underwear. That way, a person can generate electricity for electronics when they walk or bend over.
It may seem counterintuitive when designing piezoelectric components that you don't need the best materials for generating electricity. For example, instead of choosing a material that can convert 5% of mechanical energy into electrical energy, scientists may use materials that have a conversion efficiency of 2 percent or less. If it translates more, "it may do so by putting more load on the body, but the user certainly doesn't want to get tired from that," Dagvilen said.
Another energy harvesting method is to use thermoelectric conversion materials to convert bulk heat into electrical energy. "Your heart beats more than 40 million times a year," Dagviren points out. All of this energy is dissipated as body heat—a potential resource that can be captured.
Human thermal power generation does face some major problems. This type of energy conversion often relies on temperature differences, but the body's body temperature often remains fairly constant, so the temperature differences within the body are not high enough to generate a lot of electricity. However, if these devices could be exposed to a relatively cool external environment while collecting body temperature, the problem could be solved.
Scientists are exploring heat-generating devices for wearable devices, such as powering watches. The heat produced by the human body could, in principle, generate enough electricity to power wireless health monitors, artificial hearing aids and cerebral cortical stimulators for Parkinson's disease.
In addition, scientists are also trying to power devices through the common electrostatic effect. When two different materials collide or rub against each other repeatedly, the surface of one can grab electrons from the surface of the other, accumulating an electric charge, a phenomenon known as triboelectric electrification. A key advantage of triboelectric electrification is the ability of nearly all materials, both natural and synthetic, to generate static electricity, which opens up many possibilities for researchers to design a wide variety of gadgets.
“The more I study triboelectricity, the more exciting it is, and the more applications it may have,” said Georgia Tech nanotechnology expert ZhongLin Wang, co-author of the paper. “I can Seeing myself committing to this research for the next 20 years."
The amount of electricity produced by different materials through triboelectricity varies widely, so scientists are experimenting with a variety of materials. The researchers made grids of cubes that resemble microscopic city blocks, nanowires that resemble bamboo forests, and pyramid arrays of the kind that resemble the Great Pyramid of Giza. Not only do these materials "look beautiful," Wang said, but covering the surface with an array of pyramids can increase power generation by a factor of five compared to flat panels.
Researchers have conducted experiments in mice, rabbits and pigs, where they have tested pacemakers, heart monitors and other implantable devices powered by breathing and the rapid heartbeat. "We're also investigating whether we can use triboelectricity to stimulate cell growth and accelerate wound healing," Wang said. "Also, we've started triboelectric experiments on neural stimulation to see if we can do it for neuroscience. any contribution."
Wang and his colleagues also designed wearable devices that are triboelectrically charged. For example, they made triboelectric cloths that can charge flexible wristbands with lithium-ion batteries. The gadget powers a Bluetooth-enabled wearable heart rate monitor, which transmits its data wirelessly to a smartphone. "The mechanical energy generated by human movement every day can be converted into electricity through our cloth," Wang said.
Another strategy relies on devices called biofuel cells, which generate electricity through chemical reactions between enzymes and energy-storage molecules in the body, such as glucose in the blood, or lactate secreted in sweat. For example, cellobiose dehydrogenase extracted from fungi can break down glucose and generate electrical currents in nanometer (billionth of a meter) carbon tubes.
Enzyme selection can be tricky. For example, while several scientists have found that glucose oxidase can generate electricity in biofuel cells implanted in laboratory mice, the enzyme also produces hydrogen peroxide (a common bleach component), which may It will deteriorate the performance of the device and cause bodily harm.
In another study, scanning electron micrographs showed that carbon nanotubes used in an experimental biofuel cell were able to generate electricity from the body. The tubes are coated with enzymes that process natural energy molecules, such as lactate in sweat or glucose in the blood. The tool is electroactive while providing a huge surface area for enzymes to react with energy, allowing more electricity to be generated for a given volume.
French scientists have also created a biofuel cell based on enzyme-coated carbon nanotubes that is about half a teaspoon in size and, when implanted in mice, can generate enough electricity to power an LED or digital thermometer by reacting with blood sugar . Experiments have also shown that fabric biofuel cells woven into headbands and wristbands can generate enough electricity to power watches through the chemical reaction of lactic acid in milk and sweat with enzymes.
As far as Dagvilen is aware, none of these devices are currently on the market. But she predicts the technology will be on the market in less than a decade. In the future, energy harvesting devices may become more suitable for the human body. Dagvilen and her colleagues are even working on degradable power-generating gadgets.
"Imagine," she said, "putting a device in your body, and after a while it degrades into molecules that dissolve into body fluids, and you can take it out without opening your chest: we can use biodegradable Materials such as silk and zinc oxide that decompose over time."
