Nanometric-sized water drops are everywhere - in the air as droplets or aerosols, in our bodies as medication, and in the earth, within rocks and oil fields. To understand the behavior of these drops, it is necessary to know how they interact with their hydrophobic environment. This interaction takes places at the curved droplet interface, a sub-nanometric region that surrounds the small pocket of water. Researchers from EPFL, in collaboration with the institute AMOLF in the Netherlands, were able to observe what was going on in this particular region. They discovered that molecules on the surface of the drops were much more ordered than expected. Their surprising results have been published in Nature Communications. They pave the way to a better understanding of atmospheric, biological and geological processes.
Nanometric-sized water drops are everywhere - in the air as droplets or aerosols, in our bodies as medication, and in the earth, within rocks and oil fields. To understand the behavior of these drops, it is necessary to know how they interact with their hydrophobic environment. This interaction takes places at the curved droplet interface, a sub-nanometric region that surrounds the small pocket of water. Researchers from EPFL, in collaboration with the institute AMOLF in the Netherlands, were able to observe what was going on in this particular region. They discovered that molecules on the surface of the drops were much more ordered than expected. Their surprising results have been published in Nature Communications. They pave the way to a better understanding of atmospheric, biological and geological processes.
Unique perspective on miniscule droplets
At EPFL, Sylvie Roke, director of the Julia Jacobi Chair of Photomedicine -Laboratory for Fundamental BioPhotonics, has developed a unique method for examining the surface of these droplets that are as thick as one thousandth of a hair, with a volume of an attoliter (18 zeros after the decimal point). "The method involves overlapping ultrashort laser pulses in a mixture of water droplets in liquid oil and detecting photons that are scattered only from the interface", explains Roke. "These photons have the sum frequency of the incoming photons and are thus of a different color. With this newly generated color we can know the structure of the only the interface."
Read more at Ecole Polytechnique Fédérale de Lausanne
Image: The method involves overlapping ultrashort laser pulses in a mixture of water droplets in liquid oil and detecting photons that are scattered only from the interface. (Credit: © EPFL/Julia Jacobi Chair of Photomedicine - Laboratory for Fundamental BioPhotonic)
