Developing next-generation textiles for personal thermal management

Thermal comfort is significant for the human body. The human body is a very delicate system that has a narrow temperature operation range (normal temperature range at rest: 36 °C to 38 °C). Both high temperature and low temperature are usually harmful and even life-threatening. Nevertheless, to maintain thermal comfort, we still tend to rely on the ambient environment temperature control for thermal comfort until now, such as utilizing the heating, ventilation, and air conditioning (HVAC) system. Insufficient attention has been paid to the textiles we wear every day which are the interface of energy exchange between the ambient and the human body. In my Ph.D. study, I focused on the human body itself and its local environment, explored novel materials and tailored thermal regulation properties for textiles, to realize improved personal thermal management. In Chapter 1, I will introduce the background of human body thermal comfort, basic heat dissipation routes including radiation, conduction, convection and evaporation, and the personal thermal management strategy. This thermal regulation strategy is effective for providing enhanced thermal comfort and decreases dependency on the environment for the human body. Besides, considering the huge thermal mass of the entire environment as compared to the individuals, personal thermal management may help save considerable energy for building heating and cooling. The state-of-the-art textiles for thermal comfort will be generally introduced in this chapter as well. Aiming at controlling human body thermal radiation mainly in the mid-infrared (mid-IR) wavelength range, I will demonstrate the radiative cooling textiles based on polyethylene (PE) in Chapter 2. Nanoporous polyethylene (NanoPE) fibers with cotton-like softness that is mid-IR transparent and visibly opaque were explored with large-scale continuous production technology. Utilizing industrial knitting/weaving techniques, NanoPE fabrics were realized by massively produced NanoPE fibers, showing a 2.3 °C cooling effect corresponding to over 20 % of indoor cooling energy saving, compared to commercial cotton fabric of the similar thickness. Besides superior cooling effect, the nanoPE fabric also displays impressive wearability and durability. Furthermore, through identifying and utilizing unique inorganic pigment nanoparticles that have negligible absorption in the mid-IR region and compounding them into polyethylene matrix, colored radiative cooling textiles based on polyethylene were achieved. In Chapter 3, I will show the work of developing advanced textile for personal perspiration management. Integrating the water transportation channels and heat transport matrix together, the integrated cooling (i-Cool) textile not only shows the capability of liquid water wicking, but also exhibits superior evaporation rate than traditional textiles. Furthermore, compared with cotton, about 2.8 °C cooling effect causing less than one-third amount of dehydration has also been demonstrated on the artificial sweating skin platform with feedback control loop simulating human body perspiration situation. Moreover, the practical application feasibility of the i-Cool textile design principles has been validated as well. Owing to its exceptional personal perspiration management performance in liquid water wicking, fast evaporation, efficient cooling effect and reduced human body dehydration/electrolyte loss, the i-Cool textile can utilize sweat much more efficiently, which is significant for expanding human body activity and adaption limit. Next in Chapter 4, I will introduce a bifunctional asymmetric textile with tailored heat conduction and radiation regulation for personal cooling and warming. A facile surface modification approach applied on an asymmetric textile was demonstrated to realize the bifunctional textile with both cooling and warming modes. The engineered heat conduction and radiation properties in either mode resulted in improved cooling/warming effect. Plus, the expanded difference of heat conduction and radiation in cooling and warming modes also enlarged the thermal comfort zone for the human body with one piece of textile. Finally, in chapter 5, I will summarize my Ph.D. work and prospect the future work that can be explored in the near future

Keywords: Materials Science and Engineering.
Advisor: Cui Yi
Brongersma Mark L.
Fan Shanhui