Multiple parameters affect the ways in which a liquid interacts with a surface. To get a handle on those quasi-infinite possibilities, researchers at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg, Germany, have developed simulation software that predicts how liquids will behave on flat, curved or structured surfaces made of various materials. The software will help scientists optimise so-called self-cleaning surfaces and, for example, lead to the development of eyeglasses that repel rainwater. Diagnostic products also stand to benefit: microfluidic systems must be perfectly free from residual liquids to produce accurate results, and this software can help engineers develop systems that are better able to achieve those objectives.
The program at IWM simulates the form the liquid droplets take on the surface, indicating whether the liquid distributes itself over the surface or forms droplets to minimise contact with the surface, explains Dr. Adham Hashibon, Project Manager. The program also calculates flow behaviour, taking into account various factors at different scales of measurement. “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 within the simulation so that we are able to clearly reproduce our experimental findings,” says Hashibon.
The simulation is useful in medical technology applications, notes the institute in a press release. Microfluidic systems, such as constant-flow cuvettes, are used to analyse tissue cells or parts of DNA. Liquid containing dissolved substances is analysed as it flows through tiny channels and minute chambers, and it is essential that the device be free of any remaining liquid once the procedure has been completed. Residual drops would mix with a new sample and distort findings. The simulation will be used to help optimise such microfluidic systems and to design surfaces that will retain as little liquid as possible.
This tool can also be used to implement a kind of traffic management system within the microfluidic system, according to IWM. 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 in one direction, while other components take an alternate route. This technique can be used to heighten the concentration of certain molecules and is especially important, for instance, in raising detection sensitivity.