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March 2019

Generating Electricity with Superhydrophobic Surfaces and Ocean Waves

We know that superhydrophobic surfaces are super useful. Self-cleaning cars, toilet plungers, shower curtains, and treatments for smartphones, camping gear, and visors on motorcycle helmets are just a few of the applications that can benefit from superhydrophobicity.1

It turns out that with the help of ocean waves, superhydrophobic surfaces may also be used to facilitate the generation of electricity. Researchers at UC San Diego have exploited superhydrophobic surfaces to generate voltage by moving ions over a charged surface.2 The negatively-charged nanotextured surface is optimized to reduce friction and facilitate the rapid movement of salt water along with its positively charged ions. The difference between the positive and negative ions is captured as electrical voltage.

Unlike traditional superhydrophobic surfaces which have small pockets of air under the drop, the surfaces used for harvesting power from the waves use a thin film of synthetic oil which is resistant to being washed out by the salt water. The oil improves the propagation of the electrical field and has proven in the lab to be robust and reliable. 

This technology could be harnessed to power lab-on-a-chip and other microfluidic devices. The power generated from this method could also be used to augment the solar power used by smart buoys and other oceanic sensors which transmit weather,  atmospheric, and locational data.

1 For additional applications for superhydrophobicity, see our June 2014 Newsletter.
2 Enhanced voltage generation through electrolyte flow on liquid-filled surfaces, B. Fan, A. Bhattacharya & P. R. Bandaru, Nature Communications, Volume 9, Article number: 4050 (2018)

How the Energy Industry Benefits from Contact Angle and Surface Tension
The story above about generating electricity from the ocean's waves is an example of a novel application. Below we detail a half dozen applications for contact angle and surface tension researchers working in the energy sector - in no particular order:

1. Oil producers are increasingly using fracking to extract petroleum and natural gas from shale reservoirs. By carefully lowering the surface tension of the fracturing fluid using surfactants, desorption can be enhanced and productivity can be optimized.

2. Solar fields can potentially augment the power generated by other sources. Hydrophobic coatings that provide self-cleaning properties on solar panels improve efficiency by keeping the panels working at full capacity and at lower maintenance costs.

3. Power lines plagued with icicles can lower grid reliability and increase infrastructure maintenance. By using an icephobic coating, power lines can be made to repel the buildup of ice during winter months.

Power Lines in the Winter circa 1930

4. Just as icephobic coatings can benefit power lines, they can also improve the efficiency of wind turbines in cold climates. PTFE-based coatings can add both icephobic and hydrophobic benefits to blades by lowering the surface energy.

5. Coal is one of the world's most prevalent nonrenewable energy sources. However, mining coal can present some challenges and hazards. Explosions and pneumoconiosis, sometimes called "Black Lung Disease", are two such hazards which can be reduced by controlling coal dust in the mines. Scientists measure the water contact angle on coal to better understand what surfactants can be added to water to provide an effective dedusting spray formula used by dust scrubber systems. 

6. Commercial window coatings are experiencing a renaissance. Low-emissivity glass is coated with layers of silver between layers of antireflective metal-oxide which are optically transparent but allow the visible light through while blocking the dangerous UV light. By controlling the wavelength, spectrally selective glass coatings can allow the light in but not the heat. Thin coatings of titanium dioxide increases the surface energy of glass allowing the surface to become so hydrophilic that rain will not bead up but rather spreads out flat carrying with it contaminants as it slides off in sheets. The glass dries without any spotting. Today's windows are more than a sheet of glass. Innovative coatings improve self-cleaning properties as well as lower energy and maintenance costs.

If you are working on an energy solution that requires a precise understanding of wetting properties or surface tension, we can help with instrumentation needed to quantify those metrics. We've been doing so since 1961.

If you have any interest in the hottest trend in biotech, check out our recent edition of The Spinneret which features an article on Bioprinting. ramé-hart instrument company is the world's number one fabricator of custom spinnerets used in bioprinting as well as electrospinning and electrospraying. Our spinneret products can be found at this website: www.customspinnerets.com.

Carl Clegg
Director of Sales
Phone 973-448-0305
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