Cornell University researchers have produced a high-resolution “photo album” of more than 30 shapes an oscillated drop of water can take. The results, a fundamental insight into how droplets behave, could have applications in everything from inkjet printing to microfluidics.
Susan Daniel, assistant professor of chemical and biomolecular engineering, led the study, to be published in Physical Review E, Aug. 9. First author Chun-Ti Chang, a Cornell graduate student, designed and performed the experiments, which involved a high-speed, high-resolution camera. Paul Steen, professor of chemical and biomolecular engineering, and his former student, Josh Bostwick, led the theoretical portion of the study.
Download the study, images and animations: https://cornell.box.com/droplets
“What is really special about this study is the high-quality imaging we were able to capture of these oscillating droplets,” Daniel said. “We created an imaging platform where we could look at the drop from the top, to enable us to see the characteristic shapes better than anyone has before.”
The imaging platform, which Chang has named the “Omniview” because of the different angles at which the droplet can be observed, consists of a glass slide, the droplet sitting on top, and a 50-micron-square metal mesh, like a window screen, underneath. A light is shined through the mesh holes, and deflection of the drop’s surface refracts the light, which is seen as a deformation of the mesh and captured by a high-speed camera.
The researchers mechanically oscillated the drops at varying frequencies, and observed and recorded their movements. The oscillation can be likened to when a violin string is plucked; certain natural frequencies correspond to a given length of string, the same way certain frequencies correspond to the shape of a drop of a specific size.
The researchers created a detailed table of droplet shapes according to frequency, as well as comparing these results to previous theoretical predictions involving the dynamics of oscillating droplets. Classical theories don’t capture the dynamics entirely, but new predictions, made by collaborators Steen and Bostwick, take into account the physical effect of the solid substrate in contact with the droplet and match the images in the photo album.
The researchers also observed that some of the droplets take on multiple shapes when vibrated with a single driving frequency – akin to physicists observing two different energy states simultaneously in an excited molecule.
“Without the high-speed imaging, we wouldn’t have been able to see the drops exhibiting these kinds of mixed behaviors,” Daniel said.
The detailed, clear table of oscillating drop modes should lend insight into further fundamental studies, as well as a host of applications, Daniel said. For example, NASA is interested in understanding how droplets on surfaces move in low gravity. And in high-resolution printing, the spread of a drop as it touches a surface will dictate image resolution. The surface chemistry of the roller, printer and ink will have profound effects on the technology.
The study, “Substrate Constraint Modifies the Rayleigh Spectrum of Vibrating Sessile Drops,” was supported NASA, the National Science Foundation and Xerox Corp.
Contact Syl Kacapyr for information about Cornell's TV and radio studios.
Applicability of dynamic facilitation theory to binary hard disk systems
08.12.2016 | Nagoya Institute of Technology
Will Earth still exist 5 billion years from now?
08.12.2016 | KU Leuven
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
08.12.2016 | Life Sciences
08.12.2016 | Physics and Astronomy
08.12.2016 | Materials Sciences