Researchers Create Fabric Patches for Harvesting Static Electricity

Recently, researchers demonstrated a new fabric patch that can be integrated into traditional clothing manufacturing techniques to power wearable devices by taking advantage of static electricity. What challenges does powering wearable devices present, what did the researchers demonstrate, and are such devices truly viable?

What challenges does powering wearable devices present?

Here at electropages, we have covered countless stories of advances in the wearable electronics field, and in every one of these stories, we also cover the challenges that wearable devices face. For example, traditional electronics are not flexible by nature, making them difficult to integrate into devices that are comfortable to wear. Another challenge is that while flexible electronics do exist, they lack the computational power needed to be practical, limiting them to basic sensory capabilities. 

But another major challenge faced by wearable devices that isn't often covered is wearable power sources. Even if a circuit can be made entirely flexible with all the processing power needed for common applications, trying to power such a device can be extremely challenging without the use of big, ridged batteries.

Making a battery flexible is extremely difficult, as a battery that can flex with a liquid electrolyte runs the risk of internal short circuits. For example, a lithium battery that develops an internal short circuit quickly deteriorates, releases hydrogen gas, and then catches fire due to the intense heat. That isn’t to say that there aren’t flexible battery technologies available, but those that provide a high energy density and low risk of catastrophic failure simply don’t exist.

Another option is to use wireless energy techniques that utilise magnetic fields or radio waves. A ridged energy transmitter, such as a phone, can be placed in a pocket that can transfer energy to worn devices. While this is perfectly possible, it is extremely wasteful due to the inefficiencies of wireless energy transfer. Furthermore, wireless energy transmission rarely provides enough energy to power anything of sufficient capabilities which is why it is rarely used.

Finally, energy harvesting can provide wearable devices with a source of power, but just as how wireless energy is extremely inefficient, there is generally little energy to be harvested. Solar cells are often far too large, thermal differentials are rarely large, and radio is often extremely weak.  

Researchers develop wearable fabric patches for harvesting static electricity

Recently, researchers announced the development of a yarn that harvests static electricity, which can then be used to power wearable devices. At the same time, the generated electricity can also be used for sensor purposes such as monitoring activity and measuring, which effectively doubles the capability of the new fibres. 

To make the yarn, the researchers combined polyurethane-coated copper wires and PTFE synthetic fibres that generate static electricity when rubbed against each other. From there, the energy-generating yarn was integrated into clothing to demonstrate the energy-harvesting capabilities of the new fabric as well as its sensing capabilities. In addition, the sensor was also integrated into the sole of a shoe to demonstrate its capabilities as a self-powered pedometer. 

“Our technique uses embroidery, which is pretty simple — you can stitch our yarns directly on the fabric. During fabric production, you don’t need to consider anything about wearable devices. You can integrate the power-generating yarns after the clothing items have been made.” - Rong Yin

Are such power-generating devices viable?

While the device demonstrated by the researchers can indeed generate power, whether that power can be used for larger devices remains unclear. Furthermore, what the researchers demonstrated was more akin to self-powered sensors for motion detection as opposed to a power source that can be used to power a dedicated circuit. 

Going forward, wearable devices will need to identify methods for powering that is viable using today's technology. Mobile processors of the future may be able to reduce their power consumption enough to use triboelectric energy harvesters, but devices today simply cannot operate at such low voltages and currents. 

But that doesn’t mean what the researchers have developed isn't valuable or important; it could still be used to create advanced sportswear that enables for professional athletes to monitor their performance and technique. Such sensors could also be useful in the medical field when monitoring patients, especially if patients are required to exercise and move around.