These chemicals’ shapes change on the fly – they can form triangles and other shapes when frozen, and revert to their original state once warmed back up, and they may hold the key to the development of ever-changing materials.
Contrary to previously thought, forms in nature could also develop based on the physical properties of material.
These are the findings of new study from University of Cambridge and Bulgaria’s Sofia University researchers, who reported the results in the journal Nature and highlighted the research’s potential use in creating paints, personal and household products, and pharmaceuticals.
Shapeshifting Frozen Oil
“There are many ways that non-biological things take shape,” said study lead Dr Stoyan Smoukov from Cambridge, seeking to know what drives the process, how to control it, and the links between the process in biological and artificial realms.
Through freezing oil droplets while in a soapy solution, the researchers found that the droplets shifted shapes, from triangles and octagons to hexagons and fibers. The chemicals can return to their original shape once the solution is re-warmed.
Previous techniques to create the same complex shapes were highly controllable yet lacked efficiency in the amount of material utilized or required expensive equipment.
The Matter of Morphogenesis
What could be driving this process known as morphogenesis?
This process is known in animals to control cell distribution during embryonic development as well as play a role in mature animal processes such as tumor growth. Alan Turing proposed in the 1950s that it is driven by reaction diffusion, where local chemical reactions lead substance spread through a given space.
According to recent studies, though, it is materials’ physical properties that control morphogenesis – possible anticipated by Turing but unlikely to be determined with the computer systems of his time.
Plastic Crystal Phase
Based on further probing, key in the shapeshifting of materials is the self-assembling of a plastic crystal stage forming beneath the droplets’ surface.
“This plastic crystal phase seems to be what’ causing the droplets to change shape, or break their symmetry… it’s vital we understand what causes symmetry breaking,” explained Smoukov.
Plastic crystals, a special state of matter, can be considered the alter ego of many TV screens’ liquid crystals, according to Smoukov. Both plastic and liquid crystals are deemed the transition phase between liquid and solid states.
Plastic crystals have disorder in their molecules’ orientation, which makes them extremely deformable. Droplets alter their shape along with these crystals, with the shapes’ sequence also controllable via adjusting the droplet size or lowering the temperature of the soapy solution.
Non-Living Things Mimicking Living Ones
Multiple applications using small-droplet emulsions – ranging from household items to pharmaceutical goods – are expected to benefit from this level of control detected by the team.
Flexible devices are one, and could be the first step toward gadgetry with nature adapting to the users’ needs.
For lead author and Sofia University professor Nikolai Denkov, this is the first time that the plastic crystal phase is explored for showing this much variety of shape changes. Co-author Slavka Tcholakova, too, believes this can spur more studies in soft matter and materials science.
“[I]t’s curious to observe such life-like behavior in a non-living thing – in many cases, artificial objects can look more ‘alive’ than living ones,” said Smoukov.
