At a time when astronomers around the world are reveling in new perspectives on the far-off universe, a trial on the International Space Station has provided Cornell scientists with new insights into something a little closer to home: water.
The microgravity environment of the space station, in particular, illuminated the ways in which water drops sway and spread across strong surfaces—information that could have terrestrial applications in 3D printing, splash cooling, and assembling and covering tasks.
The examination group’s paper, “Motions of Drops with Mobile Contact Lines on the International Space Station: Elucidation of Terrestrial Inertial Droplet Spreading,” was distributed Aug. 16 in Physical Review Letters. The lead creator is Joshua McCraney, Ph.D.
“Now that Paul has developed a theory, it is essentially possible to anticipate outcomes for processes like 3D printing, where liquids travel across a surface very quickly, or spraying droplets on surfaces.”
Susan Daniel
The trial and its discoveries, while fruitful, are likewise mixed. The paper’s co-senior creator, Paul Steen, the Maxwell M. Upson Professor in the Smith School of Chemical and Biomolecular Engineering in the College of Engineering, passed away in September 2020, not long before the trial was led.
“It’s miserable that Paul didn’t get to see the tests sent off into space,” said co-senior creator Susan Daniel, the Fred H. Rhodes Professor in the Smith School of Chemical and Biomolecular Engineering and Steen’s long-term partner. “We trusted that we had done a good job for him eventually, and that the paper that we created from the work would do right by him.”
Daniel started teaming up with Steen soon after she came to Cornell as an associate teacher in 2007. While her flow research is centered around the natural connection point of the Covid, her alumni work was in compound connection points and liquid mechanics—a field where Steen was propelling various hypothetical forecasts in view of how beads resound when exposed to vibrations. The two analysts quickly identified
“He knew the hypothesis and made forecasts, and I knew how to execute the trials to test them,” Daniel said. “Essentially, from the second I arrived in 2007 until he died, we chipped away at attempting to comprehend how fluids and surfaces connect with one another, and how the contact line at the connection point between them acts under various circumstances.”
Their cooperation came about in a “photograph collection” of the many potential shapes that a swayed drop of water can take. Steen later developed that task by listing the beads’ energy states as proven by those full shapes and sorting them into an “occasional table” order.
In 2016, Steen and Daniel received a four-year award from the National Science Foundation (NSF) and NASA’s Center for the Advancement of Science in Space to lead liquid element research on board the International Space Station U.S. Public Laboratory.
Because of the extreme decrease in gravity, which on the ISS is approximately one-millionth of its earthly level, space is an ideal location to concentrate on the behavior of liquids.This implies that liquid surface connections, which are so limited in scale and fast on Earth that they are basically undetectable, can be, in space, almost multiple times bigger — from microns to centimeters — and their span eases back almost 30-fold.
“It’s harder to concentrate on these drop movements, tentatively and generally, when you have gravity in your way,” Daniel said.
Steen and Daniel chose a couple of reverberation shapes from their photograph collection that they needed to investigate exhaustively, with an emphasis on how a water drop’s contact line—or external edge—slides to and fro across a surface, driving the manner in which the fluid will spread, a peculiarity that can be constrained by shifting vibration frequencies.
The group arranged careful guidelines for the space travelers to keep, packing four years of arranging into a brief trial in which everything was consistently and firmly arranged.
With the scientists checking and giving continuous feedback on the ground, the space travelers kept 10 mL water drops through a needle onto nine unique hydrophobic surfaces with shifting levels of harshness. They also constrained sets of drops to mix together, and set beads onto an oscillator and tuned its vibrations to accomplish the designated reverberation shapes. The water drops’ wobbling and shaking developments were shot, and the analysts went through the following year examining the information.
That examination at last affirmed Steen’s hypotheses about how a fluid’s thickness and surface strain control the contact line’s portability, beating the surface’s harshness.
Daniel credits co-creator Joshua Bostwick, Ph.D., a previous understudy of Steen’s and presently the Stanzione Collaboration academic partner at Clemson University, with guaranteeing that the trial results squared with Steen’s hypothetical forecasts.
“Josh had the option to continue with the hypothetical side of this work in Paul’s nonattendance, which was not something I was prepared to step into and do. “It was good to have him rejoin the group and assist us with ensuring that we had the option to remove all that we could from the information we gathered,” Daniel said. “Presently we can basically utilize the hypothesis that Paul made to make expectations, for instance, in processes where you’re showering beads on surfaces, or in 3D-printing, or where fluids spread across a surface rapidly.”
Vanessa Kern, Ph.D., was likewise a co-creator of the paper.
More information: J. McCraney et al, Oscillations of Drops with Mobile Contact Lines on the International Space Station: Elucidation of Terrestrial Inertial Droplet Spreading, Physical Review Letters (2022). DOI: 10.1103/PhysRevLett.129.084501
Journal information: Physical Review Letters
