If you were asked to design a structure that maximise the amount of diffusion what design principles would you include?

Diffusion is a process by which molecules move so our features need to be designed to maximise the amount of movement that occurs. Imagine you are trying to help people get home from a stadium after a major sporting event. One of the things that you could do to help movement would be to open as many gates as possible. In terms of diffusion this is equivalent to increasing the surface area. The alveoli in our lungs create a huge surface area to enable gas exchange to occur. You could also help people leave the stadium by making the distance between the gates and the public transport as short as possible. In terms of diffusion this is minimising the distance over which molecules have to be transported. The distance between the alveoli and the capillaries in our lungs is extremely small. It would also help people to have as many buses available as possible. Our alveoli are extremely well supplied with capillaries meaning that there is plenty of opportunity to transfer oxygen into the blood and to remove carbon dioxide from it. If we are interested in getting people home safely we wouldn't want them to rush the gates or the buses. The pressure in the pulmonary capillaries is very low because the capillaries have very thin walls to minimise the distance over which gases have to be transported. The low-pressure also slows down blood flow through the lungs enabling enough time for gas exchange to occur.