Hi all,

I'm currently working on the research of superhydrophobic surfaces, which have applications in for example self-cleaning, anti-fogging and -fouling and anti-bacterial coatings. The most useful method to characterize the wetting properties of a surface is the so-called contact angle measurement. This measurement is widely used in industry too, because it is the best way to measure the surface energy, which is an important parameter, of any solid surface, because the surface energy of solids can't be measured directly.

The angles are difficult to measure, and they are usually improperly reported in the publications, which makes it very difficult to compare the values gained by different research groups. Last summer I discovered a previously unknown droplet volume dependency which may very well solve this issue, and my supervisor developed some theory for it. Although the topic is very specialized, we got very good reviews from the peer-reviewers which all recommended the paper for publication in Langmuir, which is a very high impact factor paper for such a specialized topic.

Today, we submitted a revised version of the paper to Langmuir, and I just got an e-mail that it has been immediately published online, and is going to be in print soon.

Letter
Reliable measurement of the receding contact angle

Juuso T Korhonen , Tommi Huhtamäki , Olli Ikkala , and Robin H. A. Ras

Surface wettability is usually evaluated by the contact angle between the perimeter of a water drop and the surface. However, this single measurement is not enough for proper characterization, and the so-called advancing and receding contact angles also need to be measured. Measuring the receding contact angle can be challenging, especially for very hydrophobic surfaces. We demonstrate how to do it reliably using the common needle–in–the–sessile–drop method. Generally, the contact line movement needs to be followed and true receding movement has to be distinguished from “pseudo–movement” occurring before the receding angle is reached. Depending on the contact angle hysteresis, the initial size of the drop may need to be surprisingly large to get a reliable result. Although our motivation for this work was the characterization of superhydrophobic surfaces, we also show that this method works universally ranging from hydrophilic to superhydrophobic surfaces.




Regards,
Tommi

"In this house, we obey the laws of thermodynamics!"
-Homer J. Simpson



Edited 4 time(s). Last edit at 03/01/2013 05:14PM by Tommi Huhtamaki.