There is a study by MIT of Boston on how to perfectly separate Oreos

Whether they are Ringo or Oreo, who has never tried to separate the two cookies trying to avoid that one side was more 'creamy' than the other? And why does it seem such a difficult undertaking? While some may think it is a stupid question, for researchers at the Massachusetts Institute of Technology (MIT) in Boston, it is a very fascinating mechanical puzzle. So, they carried out tests to simulate various wafer separation techniques and try to find the one that would allow them to achieve the result. They also developed a special tool to do this, later called Oreometer.

Spoiler: they failed. No matter the type of filling or its quantity, the cream will tend to stick to a single waffle, almost always.

A non-Newtonian material As scientists explain, the cream between the two cookies behaves like a non-Newtonian material (it is a soft solid when not stressed, but when subjected to sufficient stress it begins to flow, as happens with toothpaste) and when we try to separate the two halves, by twisting them or pulling them or both, we are unconsciously imitating a typical test of rheology, that is the branch of science that studies the effects of stresses on materials.

The team therefore carried out various tests by measuring, in addition to the fluidity and viscoelasticity of the cream, the necessary mechanical moment to open an Oreo, which was equal to one-tenth of that required to unscrew the cap of a bottle while its failure stress (i.e. the force required to make the material) resembles that of mozzarella.

Scientists also had fun creating an instrument, which they called the Oreometer, which would allow anyone to open an Oreo in a scientific way. To make it, instructions in hand, you need a 3D printer and get some American pennies.

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Despite the efforts, however, in the overwhelming majority of the attempts the cream remained mostly attached to a single wafer. The question at this point is: why?

Adhesion and packaging In short, no matter how scientifically you try to divide the two pods, there is no simple way or standard that allows you to distribute the cream evenly. The reasons are not entirely clear. The phenomenon is independent of the type of filling (milk or chocolate cream or other) and also of its quantity, but the researchers think that the level of adhesion of the cream to the biscuit and variables related to production and packaging have to do with it. br>
"The videos of the production process show that the first cookie is placed, then a ball of cream is spread over that waffle before putting the second cookie on top," explained Crystal Owens, one of the authors of the research. "Apparently that little delay could make the cream adhere better to the first cookie."

Beyond the cookies Scientists may not have found the trick to perfectly separate an Oreo, but studying the properties of the cream could still be useful in the design of complex fluid materials. "My 3D printing fluids are of the same material class as Oreo cream," Owens told Mit News. "So this new understanding can help me better design inks when I'm trying to print flexible electronic components from a suspension of carbon nanotubes, because they deform in almost exactly the same way."

The research has been published. in Kitchen Flows (a special issue of Physics of Fluids magazine conceived during the pandemic lockdown, when labs were mostly closed) and the authors hope it can be inspirational outside of labs too. "The best scientific research, even at MIT, - concluded Owens - is driven by the curiosity to understand the world around us, when someone sees something strange or unknown and takes the time to think 'why does this happen?' ".