Biphilic jumping-droplet condensation

Robust and durable liquid-repellent surfaces

“…76g and h), and a 100% higher heat transfer flux was obtained at large surface subcooling, for example, heat flux of B280 kW m À2 was realized when DT = 28 K. Patterning superhydrophobic surfaces with wettability contrast (i.e., designing biphilic surfaces) is also demonstrated to be capable of delaying the flooding phenomenon at high surface subcoolings so as to improve their heat transfer performance. 34,35,444,446,723,[727][728][729][730] For example, Hou et al reported enhanced heat transfer via recurrent filmwise and dropwise condensation on a beetle inspired superhydrophobic surface with hydrophilic patterns. 446 They fabricated microscale SiO 2 patterns on Si wafer using standard photolithography and oxide etching processes, and then obtained micropillars with SiO 2 tops by etching using tetramethylammonium hydroxide, which was followed by a modified deep reactive ion etching process to construct nanograss on the valleys of the micropillar arrays.…”

“…Recently, Hoque et al coupled individual droplet growth and condensation heat transfer with droplet-jumping dynamics to optimize the design of superhydrophobic nanostructured surfaces with wettability contrast patterns for maximum heat flux. 730 They reported that the wettability of the patterns should not be optimized to minimize droplet adhesion while maximizing individual droplet growth rates rather than toward minimizing droplet nucleation energy barriers. It was found that a higher RCA of the patterns minimized individual droplet adhesion, and lower pattern pitch ratio (i.e., the ratio of the pitch between neighboring patterns to the diameter of the patterns) minimized individual droplet thermal resistance during condensation, which could favor a higher global jumping-droplet condensation heat transfer.…”

Manipulation of droplets and bubbles for thermal applications

“…As shown in Figure 3b, droplets only nucleate on the hydrophilic SiO 2 , which allows precise control of the nucleation density for optimum thermal transport. Hoque et al 40 showed that proper design of the biphilic surface can significantly enhance the condensation heat transfer performance. Recent works also demonstrated various strategies to fabricate scalable biphilic surfaces 41,42 .…”

“…Hoque et al 40 showed that proper design of the biphilic surface can significantly enhance the condensation heat transfer performance.…”

Visualizing and disrupting liquid films for filmwise flow condensation in horizontal minichannels

“…One approach for enhancing condensation in microchannels is to coat the surface in hydrophobic substance such as Teflon, which transitions the filmwise condensation into dropwise condensation, resulting in enhancements up to 10 times, yet coatings are not always durable (Miljkovic and Wang, 2013;Chen and Derby, 2016;Chen et al, 2017;Antao et al, 2020;Hoque et al, 2022). However, durable hydrophobic coatings remain an active research area, thus condensation processes in industry are filmwise condensation instead of dropwise condensation (Ahlers et al, 2019;Chang et al, 2020).…”