(7di) Light and Heat-Managing Nanomaterial for Energy Efficiency and Human Health

Light is one of the most useful high-grade energy sources. Heat, on the other hand, is extremely ubiquitous but less straightforward to manipulate. Controlling light and heat smartly and efficiently would bring huge benefits for fields such as sustainable energy, power electronics and human health. Indoor temperature control contributes to 12% of the total energy consumption in the USA, and energy demand for cooling is very likely to increase due to global warming. To tackle this problem, I focused onto the most universal way of heat transfer from the human body, that is, thermal radiation. When indoors, sweat evaporation and wind convection are minimal, and radiation contributes 50% of the total heat flux. However, traditional textiles are all opaque in mid-infrared and thus are radiatively resistive. By using the principle of polymer spectroscopy and size dependence of electromagnetic wave scattering, I found a material that can be the “coolest” material for textile – nanoporous polyethylene (nanoPE). NanoPE is transparent to human body radiation but appears opaque to human eyes. Its interconnected nanopores also provide great vapor permeability for humid air. Experimentally, nanoPE can be 2°C cooler than cotton, which can save 20% of energy. Based on this new class of material, the radiative thermal property of textile can finally be explored and benefit the next generation smart cloth and wearable technology. For example, following up the first finding of nanoPE, I developed the textile which can perform both cooling and heating, without any additional energy input. My colleague and I also expand the cooling textile to outdoors, again using the light management concept. My future research interest would like to include other heat transfer routes, e.g., moisture control, convection control, onto the radiative-smart textile. Also, I am interested in applying my knowledge in nanomaterials, heat pumps, and microfluidics onto human body thermal management, which can greatly expand the applicability from ordinary to extreme activities.

Besides textiles worn by humans, the building solar heat gain is also significantly affecting the cooling efficiency. Smart windows, which can electronically control their transparency, can reduce the amount of sunlight and therefore reducing the cooling load. However, transparent conducting film with ultra-low resistance is the bottleneck for large-scale and fast transmittance switching. Traditional transparent conducting oxides have reached the material limit and become difficult to break the trade-off between transmittance and resistivity. I used metal nanowires and graphene film to realize transparent conducting films with <1 Ω/sq sheet resistance, >95% transmittance, and >1000 cycle life. The combination of these research for light and heat management bring about exciting opportunities for energy efficiency and human health applications.

Teaching Interests:

I was the TA for a graduate level class of 100 students. The class title was nanomaterials and technology. I also mentored 15 students for their final project in the heat transfer class.

I enjoys teaching materials science, thermodynamics, materials kinetics, transport phenomena, nanoscience, semiconductor physics, electrochemistry, and other major materials science and engineering courses.

Selected publications:

1. P.-C. Hsu, A. Y. Song, P. B. Catrysse, C. Liu, Y. Peng, J. Xie, S. Fan, Y. Cui. “Radiative human body cooling by nanoporous polyethylene textile” Science, 2016, 353 (6303), 1019-1023
2. P.-C. Hsu, X. Liu, C. Liu, X. Xie, H.R. Lee, A.J. Welch, T. Zhao, Y. Cui. “Personal thermal management by metallic nanowire-coated textile” Nano Letters, 2015, 15 (1), 365-371
3. P.-C. Hsu, D. Kong, S. Wang, H. Wang, A.J. Welch, H. Wu, Y. Cui. “Electrolessly deposited electrospun metal nanowire transparent electrodes” JACS, 2014, 136 (30), 10593-10596
4. P.-C. Hsu*, S. Wang*, H. Wu, V.K. Narasimhan, H.Y. Lee, Y. Cui. “Performance enhancement of metal nanowire transparent conducting electrodes by mesoscale metal wires” Nature Communications, 2013, 4:2522
5. P.-C. Hsu, H. Wu, T.J. Carney, M.T. McDowell, Y. Yang, E.C. Garnett, M. Li, L. Hu, Y. Cui. “Passivation coating on electrospun copper nanofibers for stable transparent electrodes” ACS Nano, 2012, 6 (6), 5150-5156
6. B. Deng*, P.-C. Hsu*, G. Chen, B.N. C, L. Liao, Z. Ayitimuda, J. Wu, Y. Guo, L. Lin, Y. Zhou, M. Aisijiang, Q. Xie, Y. Cui, Z. Liu, H. Peng. "Roll-to-roll encapsulation of metal nanowires in graphene and plastic substrate for high-performance flexible transparent electrodes" Nano Letters, 2015, 15 (6), 4206-4213