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The strange behaviour of the oobleck can now be predicted by researchers

The strange behavior of the Oobleck can now be predicted by researchers

Oobleck is a strange material that is also referred to as a non-Newtonian fluid. This weird substance behaves sometimes as a liquid and a solid the other times. It is made of water and corn-starch entertaining children for many hours. If it is punched it appears to be solid but if picked up it flows away. 

Scientists at MIT have studied the magic substance and published a 3D mathematical model that can predict when the oobleck can change from solid to a liquid and vice versa. The findings are published in the PNAS journal. 

The scientists explain that the fine particle suspensions demonstrate drastic changes in viscosity on shear which produces interesting behavior. This is captivating to both children and rheologists. In the model, researchers have introduced a 3D continuum model with the help of mixture theory coupling the particle and fluid phases. 

The term oobleck is derived from a green substance in the book Bartholomew and the Oobleck authored by Dr. Seuss. This has fascinated researchers for a long period of time as its behavior depends on the way it is interacted with. 

The size of the particles plays an important role in this ability of the non-Newtonian fluids. The particles of corn starch are a fraction of the size of a sand grain, so due to their small size, they can be influenced by the temperature and electric charges around them. On moving slowly through the oobleck, the grains repel each other however on hitting it fast, the particles touch giving the feel of a solid. According to Ken Kamrin, mechanical engineer, MIT although this can be created very easily the rules governing it are complex.

This research can be mostly considered as a recreational work, scientists think that this modeling can be used to test oobleck for several materials such as bulletproof vests. Although it is an important question if it can stop a bullet. 

Researchers had been working on a model for wet sand but had to change it to obtain the desired oobleck variables. They ran experiments to check if the model was perfect, such as squeezing it between plates and shooting a projectile to a tank having the substance. An X shaped wheel ran through the material at different speeds to help understand the behavior. The model was able to predict the change of oobleck from liquid to solid substance and vice versa as the wheel rolled back. 

Journal Reference: PNAS


Cryptate of potassium cation

Researchers identify state of matter to possess both solid and liquid state

A team of researchers from the University of Edinburgh, Scotland used latest models of artificial intelligence (AI) to simulate what could happen if the element potassium was subjected to very high amounts of pressure, ranging from 200,000 to 400,000 times of atmospheric pressure along with heat between 400 – 800 Kelvin.

The atoms of potassium like most of the other metals behave in an ordered manner under normal circumstances. But the team of physicists identified that in case of extreme conditions, they get arranged in complex orders, the atomic core lined up in a cylindrical way, arranged in a ‘X’ shape and four chains alongside it.

The two different arrangements are called as the “host-guest structures”, the co-author of the paper, Andreas Hermann told. The resultant substance is the formation of two intertwined and interlinked lattices which is very unusual.

The study has been published in the journal PNAS in this week and it is reported that in these conditions, potassium atoms possessed an arrangement which is called as the chain-melted state where one lattice known as ‘guest’ lattice dissolved to form liquid while the ‘host’ lattice remained as a solid form. On heating this, the guest atoms melt while the atoms belonging to the host lattice remain crystalline.

The reason behind this is that the host lattice possesses a much stronger bond and thus it remains in the solid state. This is why, a larger amount of energy is needed to melt it. On the other hand the ‘guest’ lattice has a much weaker bond, so it dissolves to turn to a liquid. The two structures, ‘host’ and ‘guest’ lattice comprising of 80% and 20% composition are similar to each other on an atomic level. The only difference between them is on their arrangement in the lattice.

When this substance is observed by the human eyes, it would appear as solid block of potassium which is dissolving to liquid as well as forming a solid structure simultaneously. The team described it as a ‘sponge-like’ material which can soak up the liquid. It can be understood as the sponge which soaks itself up, when it is a liquid and then again reforms itself in the solid state. As the host is 80% and the guest is 20%, the material is always in this state.

This was made possible by AI models and then the findings were tested over a large number of theoretical samples. As a result, the machine learning model can also determine the behaviour of the other elements in similar extreme conditions.