Personal Thermal Management by Radiative Cooling and Heating

Maintaining thermal comfort within the human body is crucial for optimal health and overall well-being.By merely broadening the setpoint of indoor temperatures,we could significantly slash energy usage in building heating,ventilation,and air-conditioning systems.In recent years,there has been a surge in advancements in personal thermal management(PTM),aiming to regulate heat and moisture transfer within our immediate surroundings,clothing,and skin.The advent of PTM is driven by the rapid development in nano/micro-materials and energy science and engineering.An emerging research area in PTM is personal radiative thermal management(PRTM),which demonstrates immense potential with its high radiative heat transfer efficiency and ease of regulation.However,it is less taken into account in traditional textiles,and there currently lies a gap in our knowledge and understanding of PRTM.In this review,we aim to present a thorough analysis of advanced textile materials and technologies for PRTM.Specifically,we will introduce and discuss the underlying radiation heat transfer mechanisms,fabrication methods of textiles,and various indoor/outdoor applications in light of their different regulation functionalities,including radiative cooling,radiative heating,and dual-mode thermoregulation.Furthermore,we will shine a light on the current hurdles,propose potential strategies,and delve into future technology trends for PRTM with an emphasis on functionalities and applications.

A new cross-scaling method to deal with the porous flow problem

The finite volume method （FVM） and the lattice Boltzmann method （LBM） are coupled with each other to construct a new cross-scaling method to deal with the porous flow problem. To check the effectiveness of our developed cross-scaling LBM-FVM, the above mentioned problem is also solved by the well known LBM-LBM. Based on the data checking of the published data and the results of LBM-FVM and LBM-LBM, good agreement is observed.

Water Responsive Fabrics with Artificial Leaf Stomata

Due to fiber swelling,textile fabrics containing hygroscopic fibers tend to decrease pore size under wet or increasing humid-ity and moisture conditions,the reverse being true.Nevertheless,for personal thermal regulation and comfort,the opposite is desirable,namely,increasing the fabric pore size under increasing humid and sweating conditions for enhanced ventila-tion and cooling,and a decreased pore size under cold and dry conditions for heat retention.This paper describes a novel approach to create such an unconventional fabric by emulating the structure of the plant leaf stomata by designing a water responsive polymer system in which the fabric pores increase in size when wet and decrease in size when dry.The new fabric increases its moisture permeability over 50%under wet conditions.Such a water responsive fabric can find various applications including smart functional clothing and sportswear.

Piezoelectric Properties of Three Types of PVDF and ZnO Nanofibrous Composites

Piezoelectric materials are highly desirable for wearable electronics and energy harvesting.Piezoelectric PVDF/ZnO com-posite nanofibers are particularly desirable for their nontoxicity,breathability,and flexibility.Here,we investigated three methods of fabricating PVDF and ZnO composite nanofibers aimed at optimum piezoelectric responses.It was found,(1)adding ZnO nanorod as fillers within the PVDF nanofiber did not improve piezoelectric response due to the fact that the process made the material more dielectric;(2)ZnO nanorods on the PVDF surface increased the power output due to the combined effects of piezoelectricity of ZnO nanorods as well as the triboelectric response of the increased surface roughness;(3)electrospraying pre-synthesized ZnO nanorods on PVDF nanofibers resulted in the highest piezoelectric response due to the combined effect of the greater piezoelectricity of aligned ZnO nanorods and PVDF nanofibers,and larger triboelectric response from increased surface roughness.

Reduced graphene oxide-based calcium alginate hydrogel as highly efficient solar steam generation membrane for desalination

Solar-driven evaporation has been considered as one of the potentialmethods for desalination and sewage treatment.However,optical concentrators andcomplex multi-component systems are essential in advanced technologies,resulting inlow efficiency and high cost.Here,we synthesize a reduced graphene oxide-basedporous calcium alginate(CA-rGO)hydrogel which exhibits good performance in lightabsorption.More than 90%of the light in the whole spectrum can be absorbed.Meanwhile,the water vapor escapes from the CA-rGO film extremely fast.The waterevaporation rate is 1.47 kg·m^(-2)·h^(-1),corresponding to the efficiency 77%under only 1 kW'm 2 irradiation.The high evaporation efficiency is attributed to the distinctive structureof the film,which contains inherent porous structure of hydrogel enabling rapid watertransport throughout the film,and the concave water surfaces formed in the hydrophilicpores provide a large surface area for evaporation.Hydrophobic rGO divides theevaporation surface and provides a longer three-phase evaporation line.The test onmultiple cyclic radiation shows that the material has good stability.The CA-rGO hydrogelmay have promising application as a membrane for solar steam generation indesalination and sewage treatment.