Blood can now generate electricity! Future wearables can probably grow directly in the body
Release date: 2017-09-28 To stay alive, our body consumes 2,000 to 2,500 calories a day, enough to power a moderately used smartphone. Therefore, if some of these energies can be siphoned, then our body can theoretically run any number of electronic devices, from medical implants to electronic contact lenses, all without batteries. Source: 36æ°ª Activated Carbon Filter,Oil Water Separator,Carbon Filter,Filter Oil Hangzhou Zhongju air separation equipment manufacturing Co., Ltd , https://www.hzzjkfzz.com
Wearables are indeed commonplace for us today, whether it's a VR helmet or a smart bracelet, but almost all wearable devices on the market today face the problem of battery life. Although these products are close to our bodies, they still need to be driven by batteries.
Scientists have also been thinking about ways to use the human body to power wearable devices. The current successful programs include heartbeat, foot and muscle motor. 
Flexible nanogenerators generate electricity through foot movements Source: Fang Yi/Science Advances 
Nano-generators generate electricity through skin and muscle movements Source: National University of Singapore
Recently, Fudan University's research team has unlocked a new "bio-powered" skill, which relies on blood to generate electricity. They implanted a 0.8 mm diameter fiber into a person's blood vessels and then extracted energy from the flowing blood. 
Carbon nanotube fibers implanted in blood vessels to generate electricity Source: Fudan University Wiley
In order to make such fibers, the researchers used two methods, one is to wrap the plastic fibers with ordered carbon nanotubes, and the other is to simply twist the carbon nanotube sheets to maintain the yarn shape.
Researchers say their system is a mini version of hydropower, but the principles are different. When the carbon nanotube fibers are in contact with the salt solution, an electric double layer is formed between the immersed nanotubes and the solution, the surface of the nanotubes is negatively charged, and the thin layer of the solution is positively charged. As the solution flows, the negative ions in the solution and the electrons removed from the nanotubes will attempt to balance the electric double layer, so that the front of the fluid has more charge, causing a potential difference across the fiber, producing voltage and current. However, this method has not achieved much success.
Other teams have created nanotube-based yarns that can generate electricity when twisted and stretched. The general principle is to insert fibers into the nanotubes, then connect a copper wire to the ends of the tube and let the salt solution flow through. it. The results show that the power generation efficiency of this method exceeds 23%. The researchers say the figure is higher than the fiber-based energy harvesting device previously reported by the media. Moreover, the longer the fiber, the faster the flowing liquid, and the higher the salt concentration, the higher the efficiency of the output electricity.
A device that is about 30 centimeters long can generate 0.04 milliwatts of power, which may be enough to power very small sensors and implants. To demonstrate its in vivo application, the researchers connected three 10 cm long fibers to the sciatic nerve of the frog and found that the frog produced a slight muscle contraction when the fibers were immersed in a flowing saline solution.
The fiber can also be woven into textiles in the future to make clothes that can generate electricity, the researchers added.
In fact, biological organisms are a potential energy field. Our bodies have energy in various forms, but most of them need to be operated to power electronic devices.
Researchers in Massachusetts, USA, successfully developed an "energy harvesting chip" in 2012 to extract electrical energy directly from the human inner ear potential (EP).
In 2013, the Sino-US research team invented a piezoelectric fiber that relies on kinetic energy to generate electricity. When the volunteer walks on the insole made of the fabric, the generated electricity is enough to illuminate 30 LED lights. Moreover, volunteers wearing a shirt with this fabric can walk a few hours to fill a lithium-ion battery.
In 2014, researchers in the United States successfully acquired kinetic energy and converted it into electricity from the heart, lungs, and diaphragms that bouncing cattle and sheep (after sedatives) by attaching ultra-thin piezoelectric materials to the organs.
In addition, our body's renewable energy also includes sweat, body temperature, tears and so on.
In 2014, a research team from San Diego, Calif., incorporated an enzyme-catalyzed fuel cell (EFC) into a wearable textile sweat belt. Volunteers wear it while riding a bicycle, sweating enough to run an LED light or a digital watch for tens of seconds.
Researchers from Australia and China successfully developed the first new fabric that converts thermal energy into electrical energy in 2015. Although it is not integrated into the garment, during the heating chamber test, the material is capable of generating electrical current through an increase in body temperature.
At first glance, tears seem to be a more unreliable source of fuel than sweat, but it is also full of energy. Tears contain substances such as glucose, lactate and ascorbate, any of which can power EFC batteries. In July 2015, researchers in Utah developed the first contact lens that integrates EFC to turn people's tears into electricity. 
Integrated EFC contact lenses
Although bio-powered fuel cells are emerging technologies that are currently sought after by the academic community and the industry, the devices that are currently invented are capable of generating less power, and there are also invasive ways of acquiring chemical energy in the body, such as blood supply. Many risks. We still have to wait for the possibility of future bio-power supply.