Two kinds of humidity-induced, bendable smart clothing have been designed to reversibly adapt their thermal insulation functionality. The first design mimics the pores in human skin, in which pre-cut flaps open to produce pores in Nafion sheets when humidity increases, as might occur during human sweating thus permitting air flow and reducing both the humidity level and the apparent temperature. Like the smart human sweating pores, the flaps can close automatically after the perspiration to keep the wearer warm. The second design involves thickness adjustable clothes by inserting the bent polymer sheets between two fabrics. As the humidity increases, the sheets become thinner, thus reducing the gap between the two fabrics to reduce the thermal insulation. The insulation layer can recover its original thickness upon humidity reduction to restore its warmth-preservation function. Such humidity sensitive smart polymer materials can be utilized to adjust personal comfort, and be effective in reducing energy consumption for building heating or cooling with numerous smart design.
Brittle intermetallics such as Cu6 Sn5 can be transformed into low cost, nonbrittle, superplastic and high temperature-resistant interconnection materials by sintering at temperatures more than 200 °C lower than its bulk melting point. Confirmed via in situ TEM heating, the sintered structure is pore-free with nanograins, and the interface is super-uniform.
This paper developed a comprehensive model which can fully explain the surface potential behavior of corona charged organic dielectric electrets. Compared to previous studies, both sides of the corona charged films were measured while they were grounded or free-standing. All films showed surface potential with the same magnitude, but opposite polarity on each side while they were measured with the other side grounded. This indicates that in contrast to the previous incomplete model, believing only the corona side containing injected charges, both sides should contain injected charges with the same magnitude but opposite polarity. This dipolar charge distribution is relatively stable and leads to a constant and controllable potential difference ΔV f between each side of the free-standing measured film. Interestingly, free-standing surface potential varied dramatically for films charged with the same parameters. This large variation is caused by the minor number of free charges, which is only ~0.1% of the corona induced dipolar charges. Therefore, in this model, dipolar charges control the surface potential difference between each side and the minor charges control the absolute value on a certain side. By manipulating them together, the surface potential on both sides can be precisely controlled.
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