News

New microscope sets a record for visualizing surface wetting properties

The microscope is 1000 times more precise than current techniques, allowing the creation of wetting maps as a new concept for hydrophobic surface characterization.
Microscope droplet probe on a butterfly wing

Wetting is an everyday phenomenon that represents how well liquid spreads on a surface. When water comes into contact with an extremely water-repellent, or ‘superhydrophobic’ surface, droplets bead up and roll off easily. Aalto University researchers have developed a measurement technique called Scanning Droplet Adhesion Microscopy (SDAM) to understand and characterize the wetting properties of superhydrophobic materials.

“Our novel microscope will promote the understanding of how wetting emerges from surface microstructures. The measuring instrument can also detect microscopic defects of the surface, which could allow coating manufacturers to control the quality of materials. Defects in self-cleaning, anti-icing, anti-fogging, anti-corrosion or anti-biofouling products can impeach the functional integrity of the whole surface,” explains Professor Robin Ras from Aalto University School of Science.

SDAM is extremely sensitive and 1000 times more precise than the current state-of-the-art wetting characterization methods. It also has the ability to measure minuscule features and inconsistencies of surfaces with microscale resolution. Existing instruments for measuring droplet adhesion forces only detect forces down to a micronewton level – not sensitive enough for superhydrophobic surfaces.

“We have used a droplet of water to measure the water-repellent properties of a surface by recording the very tiny nanonewton force when the droplet touches the surface and when it separates from the surface. By measuring on many locations with micrometer spacing between the measurement points, we can construct a two-dimensional image of the surface’s repellency, called a wetting map,” explains Professor Quan Zhou from Aalto University School of Electrical Engineering.

Wetting maps are a new concept for hydrophobic surface characterization and open a window for investigating structure-property relationships in surface wetting.

Up to now, ‘contact angle measurement’ has been the typical method of measuring wetting properties of surfaces. It is prone to inaccuracies, though, for surfaces that are highly repellent to liquid. Unlike contact angle measurement, SDAM does not require a direct line of sight, which allows measuring uneven surfaces such as fabrics or biological surfaces. SDAM can also detect wetting properties of microscopic functional features that were previously very hard to measure. Those microscopic features are important in many biochips, chemical sensors and microelectromechanical components and systems.

The research is conducted by an interdisciplinary team from three schools of Aalto University: School of Electrical Engineering, School of Science, and School of Chemical Engineering. The researchers involved in the study are Ville Liimatainen, Maja Vuckovac, Ville Jokinen, Veikko Sariola, Matti Hokkanen, Quan Zhou and Robin Ras.

More information:

The article "Mapping microscale wetting variations on biological and synthetic water-repellent surfaces" has been published today in Nature Communications.

Liimatainen V., Vuckovac M., Jokinen V., Sariola V., Hokkanen M., Zhou Q., Ras R.H.A.
Mapping microscale wetting variations on biological and synthetic water-repellent surfaces
Nature Communications (2017) 1798. 
http://dx.doi.org/10.1038/s41467-017-01510-7

Robin Ras
Professor
Aalto University
Department of Applied Physics & Department of Bioproducts and Biosystems
[email protected]
tel. +358 50 432 6633
http://physics.aalto.fi/smw

Quan Zhou
Professor
Aalto University
Department of Electrical Engineering and Automation
[email protected]
tel. +358 40 855 0311
http://eea.aalto.fi/en/research/micronanorobotics/

  • Published:
  • Updated:
Share
URL copied!

Related news

vaping
Press releases, Research & Art Published:

How vaping companies exploit Instagram for youth-oriented marketing?

Researchers use artificial intelligence to analyse hundreds of thousands of Instagram posts about vaping
Kuvituskuva: Matti Ahlgren.
Press releases Published:

Fast communications and flexibility helped grocery retailers cope with the coronavirus in spring

Research shows that daily communications, flexible planning and resourcing, and agility in action were important for helping the grocery trade get through the first wave of the coronavirus.
Rosegbach. Photo: Daniel Viviroli.
Press releases Published:

A quarter of the world’s lowland population depends critically on mountain water resources

Global water consumption has increased almost fourfold in the past 100 years, and many regions can only meet their water demand thanks to essential contributions from mountain regions
The Olli V Lounasmaa Memorial Prize 2020 awarded to JC Séamus Davis
Cooperation, Honoured, Press releases Published:

Olli V. Lounasmaa Memorial Prize awarded to Professor J.C. Séamus Davis

The winner of the 2020 Olli V. Lounasmaa Memorial Prize tells us about his research in quantum materials