Harvesting Energy from Human Movements is Now a Reality
We might be able to charge smartwatches by moving in the near future.
Led by Huanyu Cheng, a team of researchers from Penn State University, Minjiang University, and Nanjing University has devised a stretchable device that can harvest energy from human functions, such as human breathing and motion. This device can then be placed in wearable technology such as smartwatches for use. According to Cheng, the lithium-ion batteries and supercapacitors used in wearable technology have some downsides, such as short battery life and limited flexibility.
“This is something quite different than what we have worked on before, but it is a vital part of the equation. While working on gas sensors and other wearable devices, we always need to combine these devices with a battery for powering. Using micro-supercapacitors gives us the ability to self-power the sensor without the need for a battery,” said Cheng.
Micro-capacitors are alternatives to batteries and are the perfect candidate to replace the lithium-ion batteries used in wearable devices. They’re small, have long battery life, and can recharge quickly. Unfortunately, according to Cheng, conventional micro-capacitors designed for wearable technology have a “sandwich-like” stacked structure which impedes their flexibility, has a long diffusion distance, and makes integrating it into wearable technology harder.
Since this was a problem, Cheng and his team researched and explored different architectures and integration techniques. Their research concluded that arranging the micro-capacitors in an island-bridge layout did the trick. It allowed them to stretch and bend the design while reducing the deforming of the super-capacitors.
“By using an island-bridge design when connecting cells, the micro-supercapacitor arrays displayed increased stretchability and allowed for adjustable voltage outputs. This allows the system to be reversibly stretched up to 100%.” said Cheng
To construct the island-bridge layout of the cells, the team used non-layered, ultrathin zinc-phosphorous nanosheets, a material that’s great for cancer therapy, and 3D laser-induced graphene foam, graphene that’s made with laser treatment of polyamide, a polymer found in materials like silk and wool. The graphene foam is porous and capable of self-heating, thus providing drastic improvements in electric conductivity and an increase in the number of absorbed charged ions. This allowed the micro-supercapacitor to charge and discharge coherently and provide the required amount of energy to power a wearable device.
To create a self-powering system that can harvest energy from movements, the team added a triboelectric nanogenerator, a recent technology that can convert mechanical energy to electrical energy.
“When we have this wireless charging module that’s based on the triboelectric nanogenerator, we can harvest energy based on motion, such as bending your elbow or breathing and speaking. We are able to use these everyday human motions to charge the micro-supercapacitors.” said Cheng
When you put all of this together, you get a device that can convert the energy of your body’s motion to electrical energy that can be used by tech like smartwatches. The idea of powering technology using your body’s energy seems so futuristic, but it’s already here.
This research is important because this method of powering mobile devices is more eco-friendly than using batteries, which have a larger carbon footprint and contribute to e-waste. The future seems bright for battery tech, and one day, we might start walking around with this tech.
Want to know more about this technology? Read the full research paper here.
