Self-assembly of amphiphiles at an oil-water interface

What is happening here?

The molecules consist of a polar head (drawn as a red circle) which is hydrophilic (*) and `likes' to be in water, and a non-polar tail which is hydrophobic (*) (as well as being oilophillic) and doesn't `like' to be in water. Therefore the molecule is most comfortable when it has its head in water and its tail in oil. The light blue portion (the upper half) is water, whereas the grey portion(the lower half) is oil.

The molecules start at random positions and orientations. As a consequence of the amphiphilic nature of the molecules, they align with their heads in water and their tails in oil after some time. This configuration minimises the energy of the system.

Although the molecules reach a minimum energy state, they are not completely stationary. The molecules move about significantly at the interface due to thermal fluctuations. This may result in the molecules displaced from each other in the vertical direction or in the molecules tilted with respect to each other.

The undulating interface is to remind you that the interface will be in continuos motion because of thermal fluctuations and ordinary mechanical motion.

What do the buttons do?

• If the 'Restart' button is pressed, then the molecules start all over again from the same initial position. This means that the simulation will run again exacly as before.
• If the 'Start' button is pressed, then the molecules start all over again, but this time from a different set of positions: consequently they trace a different path than the previous instance of the simulation.
• The 'Pause' and 'Resume' buttons, pause the simulation and restart the simulation from where it was paused respectively.