Oscillating Droplet Tribometer. The most accurate characterization of your superhydrophobic surface.

The problem

Superhydrophobic surfaces are challenging to characterize by contact angle goniometry ^[1]. When contact angles are larger than 150°, the error in contact angle measurement grows steeply to 10° or more. Still, there is a growing need for the accurate measurement of such surfaces. 

Our solution

Prof. Robin Ras and his team developed the Oscillating Droplet Tribometer to measure the friction force between droplet and superhydrophobic surface with accuracy as small as 10 nN. The measurement principle is based on the back-and-forth oscillation of a magnetic water droplet and was published in Nature Communications^[2]. The magnetic water droplet has the same surface tension as pure water. Below is an example and a video of the measurement. 

^{[1] Liu K., Vuckovac M., Latikka M., Huhtamäki T., Ras R.H.A., Improving surface-wetting characterization, Science 363, 1147−1148 (2019). (link) (press release); [2] Timonen J.V.I., Latikka M., Ikkala O., Ras R.H.A., Free-Decay and Resonant Methods for Investigating the Fundamental Limit of Superhydrophobicity, Nature Communications 4, 2398 (2013). (link)}

Example measurement

The figure above shows Oscillating Droplet Tribometer measurements on two commercial superhydrophobic coatings that have water contact angles close to 170°. Analysis of the decaying oscillations shows large contrast in the contact angle hysteresis force (F_CAH), demonstrating that the technique can clearly distinguish small variations of wettability on repellent surfaces.

Visit also the website of Prof. Robin Ras' research group.

Interested in Oscillating Droplet Tribometry for your surfaces?

Please contact us at [email protected]