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Cake day: June 13th, 2023

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  • Abstract of the original study paper. Couldn’t get the whole paper. Behind a paywall.

    Abstract Radiative cooling significantly lowers condenser temperatures below ambient levels, enabling atmospheric water harvesting (AWH) without additional energy. However, traditional sky-facing condensers have low cooling power density, and water droplets remain pinned on surface, requiring active condensate collection. To overcome these challenges, a lubricated surface (LS) coating—consisting of highly scalable polydimethylsiloxane elastomer lubricated with silicone oil—is introduced on the condenser side in a vertical double-sided architecture. The design not only effectively doubles the local cooling power, but also eliminates contact-line pinning, enabling passive, gravity-driven collection of water. Robust AWH is demonstrated from a 30 × 30 cm2 sample in outdoor environments (of varying humidity levels and wind speeds in different months) and with no artificial flow of humidified air. In one outdoor test, the passive water collection rate of LS coating reaches 21 g m−2 h−1 double that on superhydrophobic surface, 10 g m−2 h−1. In indoor testing (20 °C and 80% relative humidity), this system achieves a condensation rate ≈87% of the theoretical limit with up to 90% of the total condensate passively collected. this approach achieves effective AWH in a decentralized approach that removes the need for piping infrastructure and external energy input









  • The purple sulfur bacteria provide strong support for the purple Earth hypothesis.

    In short, early Earth was largely anoxic. Since the sun’s energy reaches Earth’s surface most efficiently in the green region of the visible spectrum, the most energy-efficient way for early photosynthesizers would have been to absorb green light while reflecting red and blue—resulting in a purple color.

    To compete, a new group of organisms evolved that reflected green light and absorbed red and blue to make sugars. This group also produced oxygen, which was toxic to the anoxic purple sulfur bacteria. As the Earth became increasingly oxygenated, these green photosynthesizers outcompeted the purple ones.

    Purple sulfur bacteria still exist today but are limited to oxygen-free environments.