Guttman Shani, Sapir Zvi, Schultz Moty, Butenko Alexander V, Ocko Benjamin M, Deutsch Moshe, Sloutskin Eli
Department of Physics and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 5290002, Israel;
Condensed Matter Physics & Materials Sciences, Brookhaven National Laboratory, Upton, NY 11973.
Proc Natl Acad Sci U S A. 2016 Jan 19;113(3):493-6. doi: 10.1073/pnas.1515614113. Epub 2016 Jan 5.
Liquid droplets, widely encountered in everyday life, have no flat facets. Here we show that water-dispersed oil droplets can be reversibly temperature-tuned to icosahedral and other faceted shapes, hitherto unreported for liquid droplets. These shape changes are shown to originate in the interplay between interfacial tension and the elasticity of the droplet's 2-nm-thick interfacial monolayer, which crystallizes at some T = Ts above the oil's melting point, with the droplet's bulk remaining liquid. Strikingly, at still-lower temperatures, this interfacial freezing (IF) effect also causes droplets to deform, split, and grow tails. Our findings provide deep insights into molecular-scale elasticity and allow formation of emulsions of tunable stability for directed self-assembly of complex-shaped particles and other future technologies.
液滴在日常生活中广泛存在，没有平整的晶面。我们在此表明，水分散油滴可通过温度可逆调节为二十面体及其他有晶面的形状，这是液滴迄今未曾报道过的。这些形状变化源自界面张力与液滴2纳米厚界面单分子层弹性之间的相互作用，该单分子层在高于油熔点的某个温度Ts下结晶，而液滴主体仍保持液态。引人注目的是，在更低温度下，这种界面冻结（IF）效应还会导致液滴变形、分裂并长出尾巴。我们的发现为分子尺度的弹性提供了深刻见解，并有助于形成具有可调稳定性的乳液，用于复杂形状颗粒的定向自组装及其他未来技术。
