Novel wetting properties made easier through laser micromachining

April 3, 2017

Researchers at Queen’s University have developed a fast, easy and inexpensive way to create surfaces with different wetting properties for the emerging field of droplet-based microfluidics.

The researchers used laser micromachining at the NanoFabrication Kingston lab to finely pattern a microarray with alternating hydrophilic (water-attracting) and superhydrophobic (water-repelling) areas. The work, recently published in the American Chemical Society journal Applied Materials and Interfaces (DOI: 10.1021/acsami.6b16363), was some of the first research to be published out of the new state-of-the-art facility.

Droplet-based microfluidics enable simple, rapid analysis of chemicals and bio-relevant materials by manipulating extremely tiny amounts of sample on surfaces that are patterned to alternately attract and repel moisture. Current analytical approaches can be expensive and cumbersome because they require complicated instruments, large amounts of sample, and lengthy processing times.

“You can learn a lot from manipulating droplets at nanolitre and sub-nanolitre volumes, but until now, creating the surfaces to do that droplet manipulation has been complex and time-consuming,” says principal investigator Richard Oleschuk of the Department of Chemistry at Queen’s.

Surprisingly, these novel surface properties take their cue from nature, mimicking the differential wetting surfaces found in a desert-dwelling beetle, which survives its arid environment by collecting dew on its wings and back.

Using a directed laser beam, the researchers generated circular hydrophilic patches on glass microscope slides that had been previously coated with a commercial water-repellant compound. They experimented with patch sizes from 100 to 1500 micrometres in diameter, and using droplets less than one nanolitre in volume (a nanolitre is one billionth of a litre).

They 3-D printed a microfluidic device to perform fluorescence-based measurements, which enabled them to quickly demonstrate how their patterned chip could be used to generate measurable, reproducible results in a cost-effective manner.

One of the benefits of this work is that is provides some starting reference points for others wanting to experiment with other materials and patterns, says Kyle Bachus, a PhD candidate who developed and executed the project. “What is really nice is that this work can be applied to various types of analysis including those that are biologically or environmentally relevant,” he says.

“With this Oxford laser system we’re able to write and mill many different patterns in a wide variety of materials. We wouldn’t be able to do any of this work without this instrument.”

“This work is a great example of the innovation that can be achieved using new technology, such as the laser in our lab,” says Graham Gibson, Operations Manager at the NanoFabrication Kingston lab and co-author of the article. “This was all made possible by the new infrastructure enabled by grants from the Canadian and Ontario governments, and support from Queen’s University and CMC Microsystems.”

The group now plans to try this approach with other, more cumbersome analytical schemes in the hopes of making them faster, easier and less expensive without sacrificing sensitivity and detection limits.

Graham Gibson
Lab Operations Manager
P: 613. 530. 4786

About NanoFabrication Kingston:
NanoFabrication Kingston (NFK) is a collaboration between Queen’s University, Innovation Park and CMC Microsystems, providing researchers and industry with access to leading-edge equipment, methodologies, and expertise for designing and prototyping microsystems and nanotechnologies.