Wednesday, 16 July 2014

Science: Step by Step how to make Electroactive slime

This is actually a really simple experiment.  In this experiment we will be learning about Electrostrictive and Dielectric Polymers and the science behind it.


 
How to conduct this experiment...

 
You will need:


  • 75g Corn flour also known as corn starch
  • 100ml oil - anything vegetable oil, sunflower oil, olive oil etc.
  • A wooden spoon - it is REALLY important that your spoon is wooden, because it is an electrical insulator
  • A balloon
  • A woolly jumper or your hair
 
STEP ONE
 
Mix the corn flour in with the oil
 
STEP TWO

Then blow up a balloon, rub it up against a jumper (or your hair!) This creates an electrical charge.
 

STEP THREE
 
Over a bowl (this bit can get messy) hold your electrically charged balloon and get a spoonful of your electroactive slime!  Allow a little of the slime to dribble off the edge of your spoon and slowly move it closer to your balloon.
 
What do you notice?
 
The electroactive slime moved towards to balloon all by itself, really weird right!


Why does this happen?

When you rub your balloon you are creating electrical charge; the electrical charge you create on the surface on the balloon is positive. 

When the electroactive slime is moved near these protons (positively charged particles) on the balloon, the tiny particles of starch, that are suspended in the liquid, floating about (as they do not dissolve in the oil) have negatively charged particles called electrons that are drawn towards the protons on the balloon.

The attraction between protons and electrons works in the same way as magnet poles do; magnets attract if they are at opposite ends - the positive end of a magnet attracts to the negative end of another magnet - this is the same with electrical particles:  the electrons are attracted to the protons.

These electrons in the slime clump together as they are drawn towards the protons on the balloon. There is such a strong attraction that you will notice the non-Newtonian liquid thicken, this means that all the protons in the slime is pushed away from the balloon at the same time as the electrons are attracted towards it. 

However, you may notice that as the liquid eerily moves towards the balloon; you might notice the slime curling, splitting, thickening and even breaking.  This happens because although the charges can't move between starch particles, as they are all coated in oil therefore insulated, they can all pack together, which helps create the weird shapes they make as it gets close to the statically charged balloon.
 
This electroactive slime works this way because it is a type of polymer called an Electrostrictive or a Dielectric Polymer.
 
Polymers like these are made up of a flexible back bone chain with side chains that branch out.
 
At the last science group, we made a human polymer chain like this:
  • I gave 15 children a piece of paper.  
  • Five of them had a piece with C written on it, the C stood for Carbon. 
  • 10 of them had a piece of paper with an H on it, this stood for Hydrogen. 
  • I asked the children with a C in their hand to stand in a row spaced as far as possible but close enough so they can hold hands - I explained this was the backbone of the polymer structure. 
  • I then asked the other ten children to put a hand on one shoulder of one of the children with a C in their hand.  Meaning that each child with a C had two children holding an H, holding on to their shoulder.


This meant that each Carbon molecule had two Hydrogen particles I told the children.  I thought it was a good way to help the children understand a bit about the molecular structure of a polymer.  I then explained that a little less close up, and remembering there are many chains in a polymer, that it would all look like a bowl full of spaghetti!
 
If you enjoyed this experiment and want to experiment more with non-Newtonian fluids, check out these experiments:
 
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