Primer on Milk
Milk droplets are electrically neutral, but they are made up mostly of water droplets which are positively charged. The water molecules are attracted to the lip of a glass container. This is why milk, when poured slowly, will dribble down the side of a glass rather than follow a gravitational pull directly downwards. It is also why you can slowly place tens-to-hundreds of pennies into a full glass of milk before any will dribble down the side - the molecular proton attraction maintains a meniscus until the thickness of the meniscus out-sizes the strength/length of the attraction.Charging The Hopper
The experiment at Rutgers is essentially as follows - Mix 2 separate grains in a hopper. Electrically charge the grains. Pour the grains slowly and allow the static discharge to separate the two grains as they cross the beard of the pour.The really interesting thing is that the grain mixture can be electrically charged by shaking it. The friction creates static electricity within the hopper. That static electricity charges the grains - which are similar, but their molecular structure is such that they receive different levels of charge.
In Action
This picture shows a small hopper containing a mixture of red and blue grains. As they are poured into a beaker, they separate into two distinct piles.
What visitors have to say about Charging Grains for Separation
