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Author ORCID Identifier

https://orcid.org/0000-0002-1851-0602

AccessType

Open Access Dissertation

Document Type

dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Chemical Engineering

Year Degree Awarded

2023

Month Degree Awarded

February

First Advisor

Trisha Andrew

Second Advisor

John Klier

Third Advisor

Wei Fan

Fourth Advisor

Yanfei Xu

Subject Categories

Other Chemical Engineering | Polymer and Organic Materials | Polymer Science

Abstract

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. 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 then show control over two electrode-performance dependent properties: film porosity and crystallinity. By tuning the reactant ratio of EDOT monomer and iron oxidant, we introduce interface-extending porosity in the films which enhances short time scale (~minutes) charging kinetics. We then show that the in-situ growth temperature of the polymer film, which has been shown to improve crystalline order, limits the self-discharge of the polymer electrodes. A proposed mechanism is presented, by which ion channels/planes in the PEDOT-Cl crystal influence long time scale (~hours) charging kinetics.

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 of the 25 wt% LiCl-H2O mixture is characterized, which shows high ionic conductivity – 1 mS/cm at -70oC, at least 1000x higher than conventional organic electrolytes in this temperature range. A low-temperature polymer gel electrolyte is then presented, forming a textile supercapacitor which efficiently powers an LED at -70oC.

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. In the wings of certain moths and butterflies, melanin microstructures interact with light to control heat. The high optical density of melanin enables broadband light absorption and efficient light interference effects to suppress thermal emission. The polar bear has similarly evolved melanin-enriched skin for photothermal capture. This effect is enhanced by its fur made of pigment-free, hollow fibers that forward-scatter light inward and inhibit heat diffusion outward. We develop a bilayer textile which combines such light and heat control elements. The bottom nylon fabric is vapor 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) and 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.

DOI

https://doi.org/10.7275/33305434

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