A computational technique reveals how tiny pillars affect the condensation of vapor onto a surface
A computational technique to analyze how water vapor condenses on a surface patterned with an array of tiny pillars has been co-developed by an A*STAR researcher. Calculations carried out using this technique reveal that water droplets preferentially form either on top of the pillars or in the gaps between them, depending on factors such as the height and spacing of the pillars .
Superhydrophobic surfaces, which strongly repel water, are promising for many applications.
© Yurok Aleksandrovich/iStock/Thinkstock
Surfaces that strongly repel water, known as superhydrophobic surfaces, are important for many industrial applications as well as self-cleaning, defrosting and anti-icing surfaces. Scientists have discovered that inherently water repellent surfaces can be made much more water repellent by patterning them with micro- or nanoscale structures.
On such surfaces, water droplets can either be suspended across neighboring protrusions or impaled between them. The transition between these two states has previously been explored experimentally and theoretically. Furthermore, the effect of microstructures on vapor condensation has been studied experimentally, but there have been few computational studies of how droplets initially form by condensation from vapor.
Now, Weiqing Ren from the A*STAR Institute of High Performance Computing and Yunzhi Li of the National University of Singapore have systematically analyzed how micropillars on a hydrophobic surface affect the condensation of water vapor. To do this, they used a powerful computational technique known as the string method, which Ren developed in a previous study.
Ren and Li used the technique to investigate the effect of parameters such as the height and spacing of the micropillars and the supersaturation and intrinsic wettability of the surface on the condensation process. They discovered that both the pathway and configuration of the initial nucleus from which droplets form ― known as the critical nucleus ― depends on the geometry of the surface patterns.
In particular, the scientists found that for tall, closely spaced pillars on a surface with a low supersaturation and low wettability, the critical nucleus prefers the suspended state, whereas for the opposite case it prefers the impaled state. By generating a phase diagram, they could determine the critical values of the geometrical parameters at which the configuration of the critical nucleus changes from the suspended state to the impaled state.
These results provide “insights into the effect of surface structure on condensation,” explains Ren, “and a quantitative basis for designing surfaces optimized to either inhibit or enhance condensation in engineered systems.”
In the future, the researchers intend to study how fluid flow affects nucleation and the wetting transition on patterned surfaces.
 Li, Y. & Ren, W. Numerical study of vapor condensation on patterned hydrophobic surfaces using the string method. Langmuir 30, 9567–9576 (2014).
A*STAR Research | ResearchSEA
Epoxy compound gets a graphene bump
14.11.2018 | Rice University
Automated adhesive film placement and stringer integration for aircraft manufacture
15.11.2018 | Fraunhofer IFAM
Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.
Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
16.11.2018 | Health and Medicine
16.11.2018 | Life Sciences
16.11.2018 | Life Sciences