Recently, researchers from the UK and Netherlands developed yarn to generate power, detect temperature differences, and measure strain. What challenges do wearable sensors face, how did the researchers develop their yarn, and what applications could it be used in?

What challenges do wearable sensors face?

Modern wearable electronics have started to increase in popularity, with most taking the form of a watch-like device. While these devices can provide conveniences such as text messaging, browsing, and alerts, they are generally bulky and nowhere near as comfortable as clothing.

The main limiting factor behind modern wearable electronics is that electronic components are ridged by nature. Since anything ridged cannot flex or bend, anything built using ridged parts will also be inherent ridged (or at least partly).

For wearable electronics to become genuinely wearable, they need to be constructed entirely from flexible components. Research into such components is widespread, and there have already been some significant achievements. For example, PragmatIC is a UK-based semiconductor manufacturer that has successfully created a flexible ARM core. However, the core is still in its early stages and wastes large amounts of energy due to using NMOS circuitry.

Sensors are another area that wearable electronics will be heavily reliant on. Wearable sensors can give great insight into personal health and statistics, and sensors that can be comfortably worn without the user knowing will be highly advantageous. However, most sensors rely on inflexible technologies, just like electronic components, which are often bulky.

Researchers develop wearable yarn

Recently, researchers from the UK and Netherlands have developed a yarn that can be woven into textiles and provide various functions, including power generation, temperature sensing, and mechanical stress measurements.

The fibres are made using a commercially available yarn called Lycra covered in a conductive copolymer poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS). This covering gives the yarn its ability to measure temperature, detect strain, and generate power.

The ability to measure mechanical stress was discovered when the researchers subjected the yarn to high amounts of strain. This caused the formation of cracks throughout the copolymer, and it is these cracks that increase the surface area of the copolymer, giving it the ability to measure strain.

While the yarn can measure temperature, this measurement is based on thermoelectricity. As such, the yarn can only detect temperature differences as opposed to absolute temperature. While this may seem like a disadvantage, it enables the yarn to produce electricity when used in reverse. The researchers estimated that 1800 strands of fibre woven into a glove could provide enough power for basic electronics. As such, the temperature difference between the user’s body and the ambient environment could potentially power future devices.

What is the potential application for such sensors?

One potential application for such textiles would be predictive diagnostics. Simply put, a user could wear a medical vest that monitors the temperature, stress, and general movement. This data is passed to an AI that looks for anomalous data while also being compared to online databases of freely available medical data. From there, the AI could spot certain conditions before they become a problem (such as dementia and Alzheimer’s), thereby giving patients more time to act.

Another use for such sensors would be the health monitoring of individuals in dangerous environments (such as mines and oil rigs). Any deviation in normal working conditions such as toxic environments or structural failure would be easily detected on a vest-worn device, which could trigger an alarm for those at a control centre.

It is unlikely that such yarn would ever provide power (as TEGs have such low efficiencies and require high-temperature difference), but its ability to be woven into textiles while providing the temperature and mechanical strain readings is highly advantageous.