A bubble is a thin membrane of liquid surrounding a pocket of air or other gas. When bubbles touch a foam is formed. Foam bubbles can be uniform in size for example, a shaving foam or random for example, bubbles made from washing up liquid. Mathematicians and physicists are interested in soap bubbles and films because they obey a series of geometric rules relating to appearance, structure and their relationship to minimal surfaces. Bubbles want to achieve an optimal order by limiting their surface area, they will shift and rearrange themselves to settle into stable configurations, using the least amount of energy. Bubbles always want to achieve a state of equilibrium.
When a foam is formed liquid immediately begins to drain from the bubble membranes or lamellae, this process is referred to as 'thinning'. At some point, a lamella thins too much to support the bubble and breaks causing the bubble to burst. If a bubble bursts the foam is out of equilibrium, the surrounding bubbles shuffle and shift to fill the gap. The process will perpetuate for each bubble that bursts. Foams always want to optimise available space and minimise their surface area, using the least amount of energy.
With reference to minimal surfaces, Joseph Plateau illustrated the phenomena by dipping a wire frame into soap solution. The resulting film always covered the least possible surface area available, proving soap films are the closest substitute for a genuine, two-dimensional entity. Plateau's theories were profound and paved the way for many significant, scientific investigations thereafter, (for additional information on Joseph Plateau and his work please refer to the 'Plateau' gallery). Interest in bubble geometries and their relationship to minimal surfaces extends beyond science. Architects have studied soap bubbles and soap film phenomena for inspiration and confirmation.
German architect and structural engineer Frei Otto's design for the large scale, tent-like canopy for the German Pavilion at the World's Fair in Montreal 1967, was based on his experiments with soap films, observing films always spread naturally amid several fixed points and covered the least surface area. The Canopy was the first of its kind: lightweight, strong, easy to assemble and inexpensive to produce and construct. Natural light flooded in and projected an inviting openness for visitors. Otto received worldwide acclaim for the innovative design and successful practical application and continued his ethos with a 70,000 square metre canopy for the Munich Olympic Park, Summer Olympics 1972.
A number of architects have been inspired and influenced by Otto's soap film canopies: Sir Norman Foster, (the Great Court at the British Museum), Nicholas Grimshaw, (the Eden Project) and Richard Rogers, (the Millennium Dome). Australian PTW Architects and ARUP Australasia engineering group designed the National Aquatics Centre for the 2008 Beijing Summer Olympics. Initial research led designers to soap bubbles and the work of Joseph Plateau, the Kelvin problem (1887) and the Weaire-Phelan structure (1993).
Lord Kelvin put forward a conundrum, how to partition a 3D space into cells of equal volume with a minimal surface area. He proposed, 14-sided truncated polyhedra would be the most efficient. Professor Denis Weaire and his Research Assistant Robert Phelan of Trinity College Dublin in 1993, superseded Kelvin's 1887 conjecture. The Weaire-Phelan structure composes 12 and 14-sided polyhedra, each of equal volume.
The design for the N.A.C. (nicknamed the Water Cube), is founded on the Weaire-Phelan structure. The Cube itself appears to be wrapped in randomly sized bubbles, in contrast to the order and uniformity of the Weaire-Phelan structure. However, the order of the Weaire-Phelan structure is lost when viewed at certain angles, PTW and ARUP based their design on these viewpoints. Genius.