It’s raining cats and dogs and even the short run out to the car leaves your vision obscured by rain on your spectacles. There might soon be no need to reach for a cloth to wipe them off. If the surface of the lens resembled that of a lotus leaf, the drops would all fall off by themselves. The practicality of such self-cleaning surfaces is not limited to eyewear. Corrosion coatings would put up a better fight against rust without the tiny puddles of water that tend to collect on top of them.
Left: Micrometer-scale structured polystyrene surfaces for use with micro-fluids. Right: Static wetting of this type of surface with water – simulation and experiment. © Fraunhofer IWM
But exactly what characterizes surfaces that do the best job of cleaning themselves? Researchers at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg have now developed simulation software that provides the answers. “Our simulation shows how various liquids behave on different surfaces, no matter if these are flat, curved or structured,” explains Dr. Adham Hashibon, project manager at the IWM. The program simulates the form the liquid droplets take on the surface, indicating whether the liquid distributes itself over the surface, or contracts to form droplets in order to minimize contact with the surface. The program is also able to calculate the flow behavior in terms of how liquids move across different surfaces, whereby the determinant factors at different scales of measurement are integrated, from atomic interactions to the impact of microscopic surface structure.
The software analyzes what goes on within a given droplet – how the individual water molecules interact with each other, how a droplet is attracted by the surface and how it resists the air. Researchers refer to a three-phase contact link between liquid, surface and air. “How liquid behaves on a surface is influenced by a great deal of parameters, including the surface characteristics of the material as well as its structure, but also by substances dissolved in the liquid. We have taken all this into account to different degrees of detail within the simulation so that we are able to clearly reproduce our experimental findings,” says Hashibon.
Improving microfluidic systems
The simulation is also useful in medical examinations. When doctors have to analyze tissue cells or parts of DNA, they often use microfluidic systems such as constant-flow cuvettes. Liquid containing dissolved substances is analyzed as it flows through tiny channels and minute chambers, and it is essential that no liquid whatsoever remains after the procedure has been completed. Any residual drops would then mix with a new sample and distort findings. The simulation will now be used to help optimize such microfluidic systems and to design surfaces so that as little liquid as possible gets left behind. “Our goal was to better understand and control the wetting behavior of liquids on structured surfaces,” says Hashibon. But that’s not all. This tool can also be used to implement a kind of traffic management system within the microfluidic system. When a channel splits into two, giving each fork a different surface structure makes it possible to separate the various components of the liquid, sending DNA molecules one way while other components are led along the alternative route. This technique can be used to heighten the concentration of certain molecules and is especially important, for instance, in raising the detection sensitivity of analysis techniques.
Dr. Adham Hashibon | Fraunhofer Research News
Scientists predict a new superhard material with unique properties
18.06.2018 | Moscow Institute of Physics and Technology
A sprinkle of platinum nanoparticles onto graphene makes brain probes more sensitive
15.06.2018 | University of California - San Diego
Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.
Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...
The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.
Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.
An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.
Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...
Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...
Water molecules exist in two different forms with almost identical physical properties. For the first time, researchers have succeeded in separating the two forms to show that they can exhibit different chemical reactivities. These results were reported by researchers from the University of Basel and their colleagues in Hamburg in the scientific journal Nature Communications.
From a chemical perspective, water is a molecule in which a single oxygen atom is linked to two hydrogen atoms. It is less well known that water exists in two...
13.06.2018 | Event News
08.06.2018 | Event News
05.06.2018 | Event News
18.06.2018 | Earth Sciences
18.06.2018 | Process Engineering
18.06.2018 | Life Sciences