January 23, 2018
11:00 AM - 12:00 PM
Speaker: Po-Chun Hsu
Postdoctoral Researcher, Department of Mechanical Engineering
Title: "Light- and Heat-Managing Nanomaterials for Personal Health and Energy Efficiency"
In this talk, I will present several nanomaterials that can manage photons and heat transfer to enhance building energy efficiency and personal health in an unconventionally effective way. The first part introduces the concept of personal thermal management. Personal thermal management focuses on controlling the temperature around the human body rather than the whole space, so it can provide the same thermal comfort with lower energy demand and shorter turnaround time. For passive personal thermal management, i.e., no additional energy input, the key parameter is the heat transfer coefficient of the clothing. Thermal radiation, as the dominant heat transfer pathways for the indoor scenario, is an extremely effective yet less explored tuning knob. I will demonstrate infrared-reflective metallic nanowires textile for heating and infrared-transparent nanoporous polyethylene (nanoPE) for cooling, both of which achieve superior heating/cooling properties than traditional textiles. The nanoPE textile is further used to fabricate the dual-mode textile that can switch between heating and cooling modes by reversing the textile. This interesting dual-modality can expand the wearers’ adaptability to ambient temperature fluctuation to maintain thermal comfort and potentially prevent cardiovascular and respiratory diseases. The second part introduces transparent electrodes and electrochromic windows. The transparent electrode is the key component for many optoelectronic devices, including photovoltaic cells, touchscreen displays, and smart windows. Transparent electrodes with both high optical transparency and low electrical resistance will greatly benefit the device performances. For building energy efficiency, smart windows are capable of changing its color to control solar heat gain by applying only a few volts of electricity, and the energy demand for indoor temperature control can be reduced. I will introduce metal nanofiber transparent electrodes with the superior electrical and optical properties and durability which can achieve electrochromic windows with high switching speed, mechanical bendability, and long cycle life. Fabricated by electrospinning and various metallization techniques, the metal nanofibers are infinitely long and well-connected and have minimal wire-to-wire junction resistance.