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3D printed fibres to enhance thermal regulation in textiles

By Alice Davies 8 December 2017

Offering a personalised approach for controlling body temperature using textiles can be much more efficient way of saving energy than current heating and cooling methods, which need millions of watts to raise or lower the temperature of an entire building. Similar approaches can be implemented in performance wear for manging thermal comfort and safety of the wearer.

In this product innovation profile, WTiN reports on one of the latest developments by researchers at the University of Maryland in the US who have developed thermally conductive 3D-printed fibres from a boron nitride (BN) and poly(vinyl alcohol) (PVA) composite.

Purpose

Develop wearable textiles capable of personal, localised cooling. Aiming to promote thermal comfort of building occupants in hot weather conditions, providing a cost and energy saving alternative to cooling the whole building. 

Approach

BN has a high thermal conductivity and specifically nanosheets of BN have a very high in-plane thermal conductivity of up to 2000 W/(m.K) due to their two-dimensional structure. To optimise this performance, it is important for the nanosheets to be well oriented and uniformly dispersed in the fibre. Homogenous BN/PVA suspensions were achieved by sonication, resulting in an ‘ink’ of suitable viscosity for 3D printing. Continuous fibres were fabricated by injecting this ink into a coagulation bath of cooled methanol solution from a needle through the 3D printer/ As-printed fibres were also subjected to a hot drawing process to further promote alignment of the BN nanosheets in the length direction of the fibre in order to optimise their thermal conductivity. The BN/PVA composite fibres can be woven or knitted with different structures as required for the application.

Results

BN/PVA fabric was found to have high thermal conductivity of 0.078 W/(m.K), higher than that of both cotton and pure PVA fabrics; ~2.2 and ~1.6 times higher respectively. A simulation of heat transfer from the body to the environment demonstrated that BN/PVA fabric had a high fabric outer temperature of 36.2°C and a high heat flux of 58.5 W/m2, suggesting that the fabric is successfully contributing to dissipation of heat away from the body thus providing a cooling effect, which is 55% greater than that of cotton fabric. An additional advantage of the dense structure provided by the aligned BN nanosheets in the fibre is improved mechanical properties, including high tensile strength of 355 MPa and a stiffness of 12.38 GPa. The researchers suggest this is likely due to the alignment of the BN nanosheets allowing for efficient load transfer across the filler-matrix interface.

Impact

BN/PVA fabrics have potential for application as wearable textiles for personal cooling of building occupants in hot weather. This would reduce the demand for temperature regulation of the building as a whole, thus reducing associated costs and energy consumption. There is also potential for application in performance wear markets where thermal management is often desirable to the maintain the performance, comfort and safety of the wearer.

Reference

Gao, et al. Three-Dimensional Printed Thermal Regulation Textiles, ACS Nano, 2017, DOI: 10.1021/acsnano.7b06295
Copyright © 2017 American Chemical Society

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