「2014年，史丹佛大學電機工程教授范善輝（音譯，Shanhui Fan）的團隊，使用半導體製程的鍍膜技術，創造出一種含有二氧化矽（玻璃）和二氧化鉿（Hafnium dioxide）的薄膜。當時他們發明的薄膜可以反射幾乎所有的光，而且能同時輻射出很多中紅外線，使得他們的薄膜產品可以將接觸物品的表面冷卻多達5℃。不過他們的發明得要使用無塵室來製作，所以成本超高，無法大規模量產。

當科羅拉多大學的材料科學家尹曉波（音譯，Xiaobo Yin）看到這個發明的論文時，他注意到范善輝團隊的設計是讓紅外線能在薄膜內部來回跳動，最終輻射出更多紅外線，這就像吉他的音箱一樣，聲波在裡面不斷反彈共振，而讓吉他的樂音變得更大聲。尹曉波的團隊計算出，如果在薄膜內放入直徑大約 8 微米（比紅血球稍大）的玻璃珠的話，能讓中紅外線輻射量大增。

他們的製作方式是，將玻璃粉與一種透明塑料原料（聚甲基戊烯, TPX）混合，然後把它們製成 300 毫米寬的薄膜，並且在其中一面塗銀，讓它具有像鏡子一樣的反射效果。如果把這個薄膜攤開來，底層的銀幾乎可以反射所有的可見光，所以就算在大太陽下曬，也不太會吸收能量。同時，薄膜也會吸收它所接觸的物體的熱量，並以中紅外線將能量輻射出去，所以這些熱能完全不會被空氣吸收，能一直傳到外太空而消散。」

原始論文在這裡，請自己設法下載。他們也都是先申請了專利，才發表這論文的。

Natural Communications 
DOI: 10.1038/ncomms13729

Received 9 Jun 2016 | Accepted 28 Oct 2016 | Published 13 Dec 2016

Radiative cooling to deep sub-freezing temperatures through a 24-h day–night cycle

Zhen Chen1,*, Linxiao Zhu2,*, Aaswath Raman1 & Shanhui Fan1

Radiative cooling technology utilizes the atmospheric transparency window (8–13 mm) to passively dissipate heat from Earth into outer space (3 K). This technology has attracted broad interests from both fundamental sciences and real world applications, ranging from
passive building cooling, renewable energy harvesting and passive refrigeration in arid regions. However, the temperature reduction experimentally demonstrated, thus far, has been relatively modest. Here we theoretically show that ultra-large temperature reduction for as much as 60 C from ambient is achievable by using a selective thermal emitter and by eliminating parasitic thermal load, and experimentally demonstrate a temperature reduction that far exceeds previous works. In a populous area at sea level, we have achieved an average temperature reduction of 37 C from the ambient air temperature through a 24-h day–night cycle, with a maximal reduction of 42 C that occurs when the experimental set-up enclosing the emitter is exposed to peak solar irradiance.