Currently, scientists are researching how to convert mechanical, thermal, and chemical energy in the human body into electrical energy through various methods such as piezoelectric effects, thermal energy conversion, electrostatic effects, and chemical reactions, thereby providing power for wearable or implantable devices. In I Sing the Body Electric, the poet Walter Whitman fondly described the 'action and power' of 'beautiful, peculiar, breathing, laughing muscles'.
More than 150 years later, MIT material scientist and engineer Canan Dagdeviren and her colleagues are using research to give Whitman's poems new meaning. They are studying a way to rely on people. A device that generates electricity by beating the heart.
The capabilities of today’s electronic products are so powerful that the computing power of smartphones far exceeds the processing capabilities of NASA’s manned equipment when the first astronauts were sent to the moon in 1969. , The rapid development of technology makes people expect more and more wearable devices or implantable devices.
The main drawback of most wearable devices and implantable devices is still battery life. The limited battery capacity limits the long-term use of the device. When the power of the pacemaker is exhausted, what you need to do is for the patient. Replacing batteries with surgery. The fundamental solution to this problem may lie in the human body because the body contains a wealth of chemical, thermal and mechanical energy. This has led scientists to repeatedly study how the device obtains energy from the human body.
For example, a person's movement while breathing can produce 0.83 watts of energy; the body's heat in calm state is about 4.8 watts; a person's arm can exercise up to 60 watts of energy. And a pacemaker only needs Five-millionths of a watt of energy can last for seven years. Hearing aids can run for five days with only a thousandth of a watt, and a watt of energy allows a smartphone to work five hours.
Now Dagvelen and his colleagues are studying how to use the body itself as a source of energy for the device. Researchers have begun testing such wearables or implantable devices on animals and humans.
One of the energy harvesting strategies involves converting energy from vibrations, pressures, and other mechanical stresses into electrical energy. This method produces so-called piezoelectricity, commonly used in speakers and microphones.
A commonly used piezoelectric material is lead zirconate titanate, but its high lead content causes concern because it is too toxic to the human body. Dagwren said, 'But if you want to decompose lead from the structure , It needs to be heated to above 700 degrees Celsius. ' Dagveron said, 'You can never reach this temperature in the human body.'
In order to take advantage of the piezoelectric effect, Daegvelen and her colleagues have developed flat devices that can be attached to organs and muscles such as the heart, lungs, and diaphragms. These devices are 'mechanical invisible' because of their mechanical properties and their The environment is similar, so it will not interfere with the normal work of these organizations during exercise.
So far, these devices have been tested on dairy cows, sheep, and pigs because the heart size of these animals is approximately the same as the size of the human heart. 'When these devices are mechanically distorted, they produce positive and negative charges, voltages And current, which can be used to collect the energy to fully charge the battery,' Dagveren explained. 'You can use them to run biomedical devices like pacemakers instead of exhausting the battery every six or seven years. After surgical replacement. '
Scientists are also developing wearable piezoelectric energy harvesters that can be worn on the knees or elbows, or placed in shoes, pants or underwear. This way, a person can walk or bend over Electronic products generate electricity.
When designing a piezoelectric element, it does not require the best material for power generation. This may seem counter-intuitive. For example, the materials used by scientists may have a conversion efficiency of 2% or less, instead of choosing 5% conversion of mechanical energy. Material for electrical energy. If it is converted more, 'it may be achieved by putting more load on the body, but the user certainly does not want to feel tired as a result,' Dagwren said.
Another energy harvesting method uses thermoelectric conversion materials to convert body heat to electrical energy. 'Your heart beats more than 40 million times a year,' says Dagveron. All of this energy is converted to body heat and dissipated. And this is precisely a potential resource that can be captured.
Human thermal power generation does face some major problems. This type of energy conversion often depends on temperature differences. However, human body temperature often remains fairly constant. Therefore, the temperature difference within the human body is not sufficient to generate large amounts of electricity. However, if these The device can solve the problem if it is exposed to a relatively cool external environment while collecting body temperature.
Scientists are exploring thermal power generation devices for wearable devices, such as powering watches. In principle, the heat generated by the body can generate enough power to provide power for wireless health monitors, artificial hearing aids, and cerebral cortex stimulators for Parkinson's disease. .
In addition, scientists also try to power the device through the common electrostatic effect. When two different materials repeatedly collide or rub against each other, the surface of one material can capture electrons from the surface of another material, accumulating electric charge. It is called friction electrification. A key advantage of frictional electrification is that almost all materials, including natural materials and synthetic materials, can generate static electricity, which provides researchers with many possibilities for designing various gadgets.
'The more I research on frictional electrification, the more exciting it is, and its application may be more and more,' said the co-author of the relevant paper, nanotechnologist Zhong Lin Wang from Georgia Institute of Technology (Zhong Lin Wang). I can see myself working on this research for the next 20 years.'
There is a big difference in the amount of electricity generated by the frictional charge of different materials. Therefore, scientists are trying various materials. The researchers produced cubic grids similar to microscopic urban blocks, similar to the nanowires of bamboo forests, and similar to Giza. An array of pyramids of the pyramid. Wang said that these materials not only look 'pretty', but also cover the surface with a pyramid array that can increase power generation by five times compared to flat panels.
Researchers have conducted experiments on mice, rabbits, and pigs. They tested pacemakers, heart monitors, and other implantable devices that provide power through breathing and heartbeats. 'We are also investigating whether friction can be used. Electricity stimulates cell growth and accelerates wound healing, 'Wang said. 'In addition, we have started a friction electrification experiment on nerve stimulation to see if we can make any contribution to neuroscience.'
Wang and his colleagues also designed friction-wearable wearable devices. For example, they created friction electric cloths that can be used to charge flexible wristbands equipped with lithium-ion batteries. This gadget can be wearable heart rate using Bluetooth technology. The watch provides power, which wirelessly transmits its data to the smartphone. 'Every day the mechanical energy generated by human motion can be converted into electricity through our cloth,' said Wang.
Another strategy relies on a device called a biofuel cell that generates electricity through a chemical reaction between an enzyme and energy storage molecules in the body (such as glucose in the blood), or lactic acid secreted in sweat. For example, The cellulose-glycogen dehydrogenase extracted from fungi can decompose glucose and produce current in nanometer (billionths of a meter) carbon tubes.
The choice of enzymes can be tricky. For example, although many scientists have found in research that glucose oxidase can produce electricity in biofuel cells implanted in experimental mice, this enzyme also produces hydrogen peroxide (a common one The bleaching ingredients), which may deteriorate the performance of the equipment and cause harm to the body.
In another study, scanning electron micrographs show that carbon nanotubes used in experimental biofuel cells can generate electricity from the body. These tubes are coated with enzymes that can process natural energy molecules, such as lactic acid in sweat. Salt or glucose in the blood reacts. This tool is electrically active and provides a large surface area for the reaction of enzymes and energy, allowing more electricity to be produced in a given volume.
French scientists have also created a biofuel cell based on enzyme-coated carbon nanotubes. The volume is only about half a teaspoon. When implanted in mice, it can generate enough electricity by reacting with blood glucose to power LEDs or digital thermometers. Experiments have also shown that fabric biofuel cells braided into headbands and wristbands can generate enough electricity through the chemical reaction of lactic acid and enzymes in milk sweat to provide power to the watch.
According to Dagvelen, these devices are not currently available, but she predicts that this technology will be marketized in less than a decade. In the future, energy harvesting devices may become more suitable for the human body. And her colleagues are even working on biodegradable power gadgets.
'Imagine,' she said, 'put a device into your body, and after working for a period of time it degrades and dissolves in body fluids. You can remove it without opening your chest: we can use biodegradable Materials, such as silk and zinc oxide that can break down over time.
