Self-healing thermoelectric material adds durability to wearables

The prototype thermoelectric material has been developed by the KAUST team in Saudi Arabia with three organic compounds.

Sensors worn on the skin or as implants can monitor valuable markers of human health, including heart rate, blood pressure, brain activity, muscle motion, calories burned and the release of certain chemicals. The ultimate goal is self-powered wearable technologies, but these will require a reliable and durable source of electricity.

Shape-shifting electronics have potential for implants and movable medical sensors

Thermoelectric material converts waste heat into electricity

Thermoelectric materials, which use temperature gradients to generate electricity, have the potential to power wearable technologies using body heat, eliminating the need for batteries. Current materials, however, lack the flexibility, strength and resilience to avoid being damaged.

A team led by Derya Baran and Seyoung Kee at KAUST have blended the highly conductive thermoelectric polymer PETOT:PSS (poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate), with dimethyl sulfoxide, an organic compound that boosts the performance of PETOT:PSS, and Triton X-100, a sticky, gel-like agent that encourages hydrogen bonding with PETOT:PSS. The research is described in Advanced Functional Materials.

“This final ingredient was essential for providing the stretchy and self-healing properties we needed,” Kee said in a statement.

The researchers used a 3D printer to deposit their mixture and then tested the thermoelectric performance of these films under duress. First, they found that the temperature difference between the two sides of the film generated the maximum power output of 12.2nW.

The team is then said to have tested the self-healing behaviour of the films by cutting them in half while they powered an LED light. “Amazingly, the light did not go out during or after cutting,” said Kee. “I repeated the cut ten times, but it continued to self-heal in less than one second and retained 85 per cent of its power output.” Additionally, when they stretched the film to around a third longer than its original size, it still provided a stable power supply.

“Wearable electronics are under continuous strain, and their power supply is prone to breaking,” said Kee. “Our material can provide constant and reliable power because it can deform, stretch, and most importantly, heal itself…Next, we must find materials with even better thermoelectric properties so that we can generate greater power in the near future.”