Oil and water.
The reluctance of these two liquids
to mix together and stay that way is so well known they
have become cliche for any two things
that do not go together well.
Currently, there are ways to mix the two,
but ultimately, they will separate again.
So what if there was a way to not only mix oil and water,
but to have the mixture remain stable
for long periods of time, perhaps indefinitely?
Well, a team of researchers at MIT
may have found a way to do just that.
Here we have oil and water represented
by the colors red and blue.
Alone, these two liquids will not mix together.
But add in a soap-like substance,
called a surfactant, then mix, and suddenly, the two liquids
will blend.
This type of mixture of two or more liquids
that are normally immiscible is called an emulsion.
Now, creating emulsions is not a new process.
Think of the mixture of oil and vinegar in salad dressings,
for example.
But the challenge is to get the emulsions
to remain stable for longer than a few minutes.
The key to overcoming ultimate separation
is to have really small, nano-sized droplets.
When the drops are that small, gravity cannot overcome them,
and they can remain suspended indefinitely.
There are ways to do this.
However, the current industrial processes
are extremely energy intensive and expensive.
The new process used in the MIT lab
requires very little energy, in fact, no mixing at all,
and can remain stable for months.
This new process takes a bottom-up approach
by using condensation to create the droplets.
First, they take a reservoir of oil with an added surfactant,
place it inside a chamber with very humid air,
and cool the oil.
As it cools, the condensing water
forms droplets at the surface that
spread through the oil-surfactant mixture,
forming uniform, nanoscale droplets.
These droplets are so tiny and uniformed that they
are hard to even see under a microscope.
The team believes the approach should
work with a variety of oils and surfactants.
This new process could provide design guidelines for use
in particular applications that have
expiration dates, like drug delivery, cosmetics,
and processed foods.