Anti-icing film that only needs sunlight
An anti-icing film that only requires sunlight to work has been developed at a South Korean institute.
The coating exploits the photothermal effect of gold nanoparticles within a spray or oil coating of anti-freeze substances. It can reportedly be applied to plastic, glass and flexible surfaces, and can generate its own heat energy in locations where frosting becomes a serious issue.
The uniformly patterning gold nanorod (GNR) particles are arranged in quadrants through evaporation, say researchers at the Korea Advanced Institute of Science and Technology (KAIST).
GNR is thought to be a promising nanomaterial for controlling substrate surfaces due to its biocompatibility, chemical stability, relatively simple synthesis, and its stable and unique surface plasmon resonance. This is where free electrons on the gold surface oscillate when the nanorods absorb light energy. Many generate vibrational kinetic energy, which then converts to thermal energy.
Group Leader Professor Hyoungsoo Kim from KAIST says this effect can occur in gold, silver and other metals – but gold exhibits the most 'outstanding characteristics' and has chemical stability, meaning it is also suitable for biomedical applications and is easily manufacturable.
Maximising GNR performance through highly uniform film deposition and a high level of rod alignment has so far proved challenging, the team notes.
They used cellulose nanocrystals (CNCs), as GNRs and CNCs are physico-chemically favourable, so they can naturally assemble in parallel during sample preparation. Co-assembling GNR on CNC quadrant templates means the film can be dried with uniform alignment in a ring shape.
The team has so far developed a printable coating ink that they deposit in a methanol-water binary mixture. They are currently trying to print it with inkjet and/or roll-to-roll printing techniques.
'Our developed material and coating technology, thanks to gold nanorods, allow for heat generation solely from light and offer a coating technology suitable for mass production, making them highly versatile. We anticipate diverse applications in fields where heat is required under light exposure conditions,' Kim says.
Currently the film is not transparent, but Kim notes this could be used for aircraft body surfaces or exposed pipes.
He says that additional research is needed for applications that need transparency. 'Implementing the film in real-world settings like car [windows] and residential spaces necessitates transparent film implementation.'
The concentration of gold in the film is less than 1wt.%. 'Assuming a gold price of US$65/g and considering the production of the specified area with a thickness of 10-20μm, coated with ink to ensure transparency, let’s estimate the approximate cost to be around US$4 to be included within the ink.'
While they do not believe this is expensive, the team is open to alternative nanomaterials with a similar surface plasmonic effect.
