Oobleck: A non-Newtonian fluid revolutionizing speed bumps

Oobleck? Yes you read it right. Thinking you have never come across this term in all your life? Well, Oobleck is nothing but a mixture of cornstarch and water. What does corn starch and water have anything to do with speedbumps? The answer can make you marvel at the human mind with its simple, yet smart thinking capabilities.

Why traditional speedbumps are a problem?

Speed bumps have been a part of the road culture for more than 5 decades now. The were introduced in the 1970s and have managed to exist till now. They are raised ‘bumps’ with 3-4 inches of thickness, used as speed reducing mechanisms for vehicles on road, specially in speed sensitive regions. While they do their purpose, there are some unwanted problems related with the usage of speed breaks, ranging from economical to health concerning issues.

Some of the problems are:

  • Inconsistent speed and abrupt slowing of vehicle due to speed bump and then picking up the speed leads to higher emission, leading to air pollution.
  • Often slow down emergency vehicles
  • May cause spinal damage to some people
  • Inconsistent speed can lead to rupture of vehicles
  • Extra cost (manpower and raw materials) involved in maintaining the road signs, painting and marking, indicating that speed bumps are ahead.

As I already mentioned, Oobleck is a corn starch slurry. This mixture is filled in long cylindrical shaped rubber reinforced tubes resembling a speed bump which is secured to the road. When vehicles pass this speed bump with a slow speed, the liquid parts and allows the vehicle to pass thorugh as if there was nothing present. But, when a vehicle with high speed tries to pass through, the liquid hardens, thus limiting the speed of the vehicle. How does that happen?

oobleck bump

An oobleck filled bump.
The speed bump deforms under the tire when vehicle approaches with a slower speed.

Non-Newtonian fluids and the science behind

Oobleck is a non-Newtonian fluid. A non-Newtonian fluid is one whose viscosity changes under stress. That is, when you apply force to such liquids, it hardens (viscosity increases) and on the release of the force, it gets back to its normal form. But other ‘normal’ Newtonian liquids do not exhibit such characteristics. On application of stress, they do not resist that stress and thus does not cause a strain. Stress is when you hit a metal with hammer and strain is the resulting dent occurred due to the stress.

Non-Newtonian fluids are not rare. We come across them in our daily life without even knowing them. For instance take tomato ketchup. Many times, you may struggle getting the ketchup out from the bottle, and you unconsciously tap the back of the bottle. And you will see that ketchup now falls into your plate. Ketchup is a non-Newtonian fluid whose viscosity decreases when stress is applied. By tapping the back of the bottle, a stress is applied and the ketchup becomes runnier, thus easily pouring out.

Some more examples are:

  • Viscosity decreases with stress over time – Honey ( on stirring honey, it becomes runny)
  • Viscosity increases with stress over time – Cream ( on whipping, it gets thicker)
  • Viscosity decreases with increased stress – Tomato ketchup
  • Viscosity increases with increased stress – Oobleck
Try it at home!

You can easily try this at home by adding 1/2 cup of water gradually to 1 cup of corn starch. After the powder is fully wet and feel like liquid, its time to get your hands messy. Dip you hands into the mixture and try making a ball. It will start to shape due to the stress you are applying with your hand. But once you stop shaping, like magic, the ball turns into liquid and oozes down. Try it and there is no going back. The inner child in you will want to play with it all day long. Visit here for more details on how to do it at home.


Shaping oobleck into a ball by applying stress.

Shaping oobleck into a ball by applying stress.


Liquified oobleck

When we stop shaping it, it turns into liquid.

An environment friendly alternative

As the speed bump works as per the speed of the vehicle, there is no need for vehicles to slow down hence increasing fuel efficiency and decreasing emissions. The cost of installing and maintenance is low compared to traditional speed bumps. It does not do damage to the vehicle as the work of shock absorbers is reduced. Hence it is high time that countries start adopting this technology and try to reduce the damages we do to the environment one speed bump at a time!