Nezha breaks through the heart-piercing curse, and the scientific principle behind it is actually this →

Review expert: Zhou Hongzhi, senior experimenter and master's supervisor at the School of Physics and Optoelectronic Engineering, Beijing University of Technology

In the movie "Nezha: The Devil Boy Conquers the Dragon King", the scene where Nezha breaks the "heart-piercing curse" is the most difficult S-level special effect, and the plot also makes the audience very worried. But today, we are not going to discuss special effects technology or the plot (we won't spoil it), we are going to discuss lotus root powder.

Because↓↓↓

When Nezha tried to break through the "Heart-Piercing Curse", all conventional struggles were unsuccessful. However, when Nezha completely relaxed and suddenly exerted force, he successfully broke through the "Heart-Piercing Curse". It turned out that this was because Nezha's essential body was lotus root starch, and lotus root starch was a non-Newtonian pseudoplastic fluid.

lotus root starch

Lotus root starch is a common food in our daily life. It is made by grinding fresh lotus roots into powder slurry, then settling with clear water, dehydrating and drying to become lotus root starch. When lotus root starch is mixed with water in an appropriate proportion to form a starch slurry, it will show a wonderful physical property - non-Newtonian fluid properties.

In lotus root starch paste, lotus root starch still remains as solid particles, but the molecules of the particles form a complex linking structure, which will produce a strain response when subjected to external forces, thus causing the lotus root starch paste to deform. When lotus root starch paste is subjected to shear forces of different sizes and speeds, the paste exhibits different fluidity, thus showing the characteristics of a non-Newtonian fluid.

Non-Newtonian fluid

Non-Newtonian fluids refer to fluids that do not satisfy Newton's experimental law of viscosity. Their viscosity changes with the change of shear forces of different properties acting on them. Under the action of shear stress, the relationship between the shear stress and the shear rate of non-Newtonian fluids is not a simple linear relationship. This characteristic causes non-Newtonian fluids to undergo strain phenomena such as stretching, twisting, and breaking when subjected to slow shear. However, under the action of rapid shear force, this viscous substance will not produce strain quickly, thus showing the hard characteristics of solid substances.

Types of Non-Newtonian Fluids

There are several types of non-Newtonian fluids:

0 1 Shear-thinning fluid (pseudoplastic fluid)

The viscosity of shear-thinning fluids decreases as the shear rate increases. This type of fluid is viscous when it is still, but once an external force is applied, the viscosity decreases and it becomes easier to flow. In layman's terms, it bullies the weak and fears the strong. If you are strong, it will be weak, and if you are weak, it will be strong.

0 2 Shear thickening fluid

Shear-thickening fluids have a viscosity that increases with shear rate. When you apply force to make them flow, they become more viscous, or "stronger when faced with stronger forces and weaker when faced with weaker forces."

0 3 Bingham plastic fluid

Bingham plastic fluids start to flow only after exceeding a certain shear stress. Below the yield stress, they behave like solids, and above the yield stress, they behave like Newtonian fluids. When you squeeze toothpaste, you will find that when there is no squeezing force, the toothpaste remains in a solid form. When the applied pressure exceeds a certain threshold, the toothpaste will flow out of the tube and show the characteristics of a liquid.

0 4Viscoelastic fluid

These fluids have both viscous and elastic properties. When subjected to external forces, they not only change shape, but may also store some energy and partially return to their original shape when the external force is removed. Common decompression silicone toys are viscoelastic fluids. When you stretch it hard, it will be stretched very long, which is a manifestation of viscosity; but when you stop stretching, it will slowly return to its original shape.

Has unique physical properties

Non-Newtonian fluids have several unique physical properties:

0 1 Jet expansion

When a non-Newtonian fluid is forced from a large container into a capillary and out of the capillary, the diameter of the jet will be larger than the diameter of the capillary.

0 2 Pole climbing effect

When you rotate the experimental rod in a beaker of viscoelastic fluid (a type of non-Newtonian fluid), the liquid surface will flow toward the center of the cup and climb up the rod, and the liquid surface will become convex.

0 3 Tubeless siphon or open siphon

For high molecular liquids, such as polyisobutylene in gasoline solution, when the tube is pulled out of the container, the liquid will continue to be drawn out of the cup and continue to flow into the tube. Even without a siphon, the beaker filled with the liquid is tilted slightly to allow the liquid to flow down. Once the process starts, it will not stop.

Applications of Non-Newtonian Fluids

Non-Newtonian fluid mechanics is widely used in chemical fiber industry, plastic industry, petroleum industry, chemical industry, light industry, food industry and other fields.

0 1 Food Processing

Non-Newtonian fluids are used as thickeners, emulsifiers, etc. to improve the taste and texture of food.

0 2Oil Extraction

As fracturing fluid and drilling fluid, it helps control the permeability of oil fields and improve production efficiency.

0 3Medical Engineering

Used to simulate blood flow and optimize the design of medical devices such as vascular stents.

0 4 Materials Science

Used to prepare high-performance materials such as nanoparticles and biodegradable polymers.