Textile Considerations for Wearable Thermal Energy Harvesting: Knit Structures and Body Mappin

To improve thermal energy harvesting from the body, a complex set of microclimates, components, and functions must be considered in relation to each other. While much literature on energy harvesting improvements highlights the importance of device and material optimization, little focus has been geared towards improving the collective textile-electronic as a whole. The objective of this work is to integrate thermal energy harvesters into a knit textile and to generate a power generation map for locations and scenarios from thermal energy harvesting on the body. A test method for evaluating the performance of a TEG in a wearable form is developed and demonstrated using both in-lab and out-of-lab procedures. The fabrication procedure of an energy harvesting wearable device demonstrates a method of integrating rigid devices into a flexible substrate. The wearable device is used in a human trial, which covered a series of activities in different environmental conditions. The outcomes of these trials demonstrate the significant effect of movement, or convection, on thermal energy harvesting. Finite-element simulations explored how convection and conduction change the heat flux through the textile and the thermoelectric generator (TEG). This research also identifies which knit properties improve thermal energy harvesting by modifying the environment immediately surrounding the TEG through finite element simulations. These simulations provide guidance on critical design considerations for integrating wearable technology with knit textiles. Textile swatches were knit and characterized accordingly for validation of the simulation results. The research shows the significant effect of stitch density on air permeability of the textile and corresponding heat flow induced by convection. These results have led to the design of a knitted shirt with structured stitches that promote energy harvesting. The shirt is used in a human trial, which covered a series of activities in different environmental conditions. The results of these trials confirm the influence of convection on thermal energy harvesting in addition to mapping energy harvesting levels over the torso. Preliminary results show that the best locations for thermal energy harvesting are at the extremities rather than the core of the body. TEGs placed on the back, torso, and side of the body showed the lowest power values for all activities performed in the trial. The results of this work quantify how smart garment design should include consideration of the use case scenario and where thermal energy harvesters are located. As wearable technology advances, this work can be referenced as a foundation for investigating textile design based on human factors and device functionality.