Simulation in microfluidics
Capillary action plays a special role in microfluidics. Miniature products, nanotechnologies and increasingly targeted and complex applications mean that the desired capillary action is not always obvious. Here, Merkle CAE Solutions specifically uses simulation methods to know how the fluids will behave even before the products are manufactured or even used.
Capillary action occurs when the adhesive forces between a liquid and the surface are stronger than the cohesive forces within the liquid. This effect can be calculated by knowing a few factors, such as the surface tension, the density of the liquid, the acceleration due to gravity, and the contact angle between the liquid and the capillary wall. Complicated if you don't know the factors exactly. Even more complicated when the geometry or materials used in a component change and additional forces, such as those due to acceleration, act.
The advantage of simulation technology for microfluidics is that these effects can be simulated even with very complex geometry, when static approximation models such as the Jurin equation reach their limits. In addition, temporal effects can also be taken into account, which play an essential role especially in laboratory measuring devices with fast cycle times.
"With the knowledge of the rise height of the liquids, processes can be optimized and materials can be developed with specific properties in a targeted manner. Therefore, it is more than desirable to be able to accurately estimate the effects in advance using simulation technologies. Especially because the complexity of products tends to increase rather than decrease. How good is simulation at calculating capillary action? The comparison with test results to accurately determine the characteristics, plays an important role. The smaller the products and the capillaries become, the more complex geometries are, the more accurate the simulation must be. Therefore, it is not only a well-founded calculation that is important, but primarily the experience of the calculating engineers. This is our trump card," says Stefan Merkle, Managing Partner of Merkle CAE Solutions GmbH.
