Avoiding Cracks in Nanoparticle Films
Often nanoparticles of different kinds are suspended in liquids as their small size makes them difficult to work with directly, but also enables them to flow with the liquid which is not as challenging to manipulate. This means that to make things from these nanoparticles, the liquid has to be removed, but when this occurs, the film of nanoparticles left behind can crack. Researchers at the University of Pennsylvania have found a way to prevent this cracking that, unlike other methods, is relatively cheap.
Because cracking like this occurs for so many materials, the critical cracking thickness is well-known for many materials as well. If a film thinner than this thickness was required, previously one would have to expose it to high temperatures or pressures, which are difficult to produce, but the researchers found a counterintuitive way around this. Instead of trying to make a single film of the proper thickness without cracks, the researchers made multiple thinner films and stacked them together. Individually these films will crack as one expects, but when combined together, the cracks no longer form and produce a pristine film of the appropriate thickness.
While a specific detail of how this method works is still unknown, the researchers believe this method could be applied to multiple materials to create crack-less nanoparticle films. Once that detail is explained, perhaps this method can be applied to even more films.