Chair: Trisha Andrew, Chemistry
Humans developed textiles to manage thermal energy transfer with the environment and support homeostasis in a wide range of climates. With the anticipation of wearable technologies to transform healthcare via early, pre-symptomatic detection of illness, there is now a demand for electrical energy storage to support such on-body devices. Finding energy materials to merge seamlessly with textiles is basic requirement to ensure widespread adoption of wearable health monitors.
Here we use a vapor deposition process to conformally coat ordinary fabrics with the doped conjugated polymer poly(3,4 ethylenedioxythiophene) (PEDOT-Cl), a soft material which possesses electronic and redox capabilities commonly associated with inorganic energy materials like lithium, nickel, copper, etc. We demonstrate PEDOT-Cl electrode threads that may be directly sewn into garments to form supercapacitors which meet the needs of low-power biometric sensors. Towards optimizing PEDOT-Cl material properties for such electrochemical applications, we show process parameter control over two electrode-performance dependent properties: film porosity and crystallinity.
We shift our attention from electrodes (electron conducting) to electrolytes (ion conducting), often the origin of low temperature performance issues in energy storage devices. Here we formulate an aqueous LiCl mixture at the eutectic concentration and demonstrate excellent performance down to -70oC. Temperature-dependent conductivity measurements of the 25 wt% LiCl-H2O mixture reveals high ionic conductivity (~1 mS/cm at -70oC), enabling efficient, low temperature energy storage.
Finally, motivated by the energy and climate crises, we revisit the design of the textile for its original function – thermoregulation – to investigate sustainable ways of supporting thermal homeostasis amidst environmental extremes. We take inspiration from polar-dwelling animals that suppress thermal emission and harvest solar heat to reduce metabolic energy needs via radiative energy management. Mimicking cold adapted moths and polar bears, we develop a bilayer textile. The bottom nylon fabric is coated with PEDOT- Cl, an optically dense organic conductor with high visible light absorption and low thermal emission. The top fabric is made of spun-bonded polypropylene fibers (Agribon AG-19) which, akin polar bear fur, acts as a semi-transparent insulator, transmitting ~85% of visible light to the photothermal PEDOT-Cl-nylon layer.
Under moderate illumination of 130 W/m2 (ca. 0.1 sun), this textile maintains the wearer’s thermal comfort down to 4.1 oC – an additional heating effect of 10oC relative to a typical cotton T-shirt that is 30% heavier. Under full wintertime sunlight (650 W/m2), the garment supports thermal homeostasis in extreme conditions as low as -28oC. As the energy and environmental crises progress, reinventing textiles with polymer-enabled light and heat control will prove increasingly useful.