Thanks to the rapid computer developments of the last decade and the miniaturization of electronic components, we can, for example, follow our movements and monitor our health in real time using small computers.
Researchers are now looking for the best way to power these devices by drawing on the user’s own body heat and working with garments, moles, and knowledge from the textile industry.
The wearable electronics market is expected to grow to € 53 billion by 2025, but it is dominated by one product: smartwatches. Outside of this, there are many products in “initial position”, says Matthias Fahland of Fraunhofer FEP in Germany. One of the main obstacles in the field is storage . “The question of where the power comes from, where is the battery, how long will it last, (storage) is the crucial question for everything.”
A project called ThermoTex is exploring the use of human body heat to power tiny devices. The thermoelectric effect has been known for nearly 200 years, according to Professor Christian Müller of the Chalmers University of Technology in Sweden. This effect allows thermal energy to be converted to electrical energy when there is a difference in temperature, such as the difference between a person’s skin and the outside temperature. Electrons move from the hottest part of a material to the coldest part, and this movement of charge generates an electric potential.
“Heat gradients (differences) are an important energy source because they are always there,” he said.
Polymers
ThermoTex has two tracks: fundamental and applied science.
For their fundamental clue, the team tried to design polymers that had better thermoelectric properties than are currently available. One way to adjust the thermoelectric effects of polymers, which are long repeating chains of molecules, is through doping. This process creates the electrical charge necessary to generate electricity.
In 2020, the ThermoTex team published a paper in Nature Materials , showing that combining polymers with low ionization energy (the energy needed to shed an electron) and a dopant (a molecule added to the polymer) with high electron affinity , it was possible to double the effectiveness of doping.
However, there are safety concerns surrounding dopants, especially when used in portable electronic devices. “They can be toxic”, clarifies Müller. If they come in contact with your skin, they can poison you, he adds.
The team has studied around 50 different dopants that they will investigate further in a large EU-funded project called HORATES starting in 2021 to develop organic or carbon-based thermoelectric generators.
As part of their applied work, ThermoTex purchased commercial conductive polymer formulations, which they used to coat silk. While these coatings are not as efficient as some of those made in Professor Müller’s lab, they allowed the project team to begin manufacturing conductive tissues and devices. The coated silk could power body monitoring sensors for vital signs, for example.
They sewed the dyed silk strands in long lines through the fabrics and also embroidered them in small polka dots, which is important, says Professor Müller, because when in ‘dot form’, the silk is a conduit between the skin. and the exterior. air. The students also wove these silk threads together on a loom.
“I think it is very important to interact with the textile industry to use their methods,” he argues. “It’s a well-established industry with low profit margins, so they can’t come up with a fancy method that no one has.”
Platform
Meanwhile, Fraunhofer researcher Fahland is also trying to offer the textile industry solutions that it can use in its garments. He is the project leader for Smart2Go, an 11-member project that aims to create a self-contained palm-sized power delivery platform for portable electronic devices.
The platform integrates the capture of energy as the energy derived from the thermoelectric effect, storage and applications of this energy. “The platform is a very functional piece of aluminum,” Fahland says, adding that he can hold it in his hand. “It is an interface that connects the energy harvester to the application. You can specify how the power is put into the platform and how it is delivered to the application. “
In terms of applications , Smart2Go is collaborating with industry partners on two different projects.
Smart2Go is working with a textile and apparel manufacturer to integrate their platform with energy harvesting materials for safer work clothing. This could include features like light up when it gets dark. You are also working with a sports and leisure apparel company to make garments that can collect performance information.
These solutions place many restrictions on the weight and flexibility of the materials, Fahland explains. Furthermore, it must be constructed in such a way that a user can “connect” different energy harvesting technologies.
Smart2Go projects are based on solar energy and body heat, but others may include energy generated from movement or kinetic energy, for example. Project colleagues at the University of Tampere in Finland are working on supercapacitors for the platform, which will increase the electrical current available for different applications by expanding the possible uses of the platform.
Mobile phone
However, these little energy harvesters can only collect a certain amount of energy from the environment. Professor Müller from ThermoTex laughs at the idea that one day the thermoelectric effect could be used to power a mobile phone.
Not only is the collection process very inefficient, he estimates that at most 1% of the thermal energy can be collected and stored, and that is why they are trying to develop new materials – it would make the user feel very cold like the device. try to take energy from your body.
However, for smaller applications, such as sensors to monitor a person’s health, identification tags or safety garments, tiny devices that extract small amounts of energy from their surroundings could be the answer.
The biggest obstacle to portable electronic devices may not be technical, although so far it has been a major impediment to their development and acceptance. The ability of portable devices to collect and store people’s private information, and the security concerns that this poses, must be addressed for portable electronic devices to continue to grow. “There are many legal and data security issues that need to be taken very seriously,” Fahland says.
Meanwhile, he and others in the field are clearing the roadblocks they can and creating the technology that will pave the way for a future where our clothing generates energy from our bodies and their environment.
Original article
This article was originally published in Horizon, the EU Research and Innovation Magazine
