Amazing Materials Quiz

Answer: In stents that open up at body temperature, and in braces wires. The stent is inserted folded into an artery, then returns to its remembered shape as it warms to 37 °C, holding the artery open. In orthodontics the wires apply a gentle, steady force. The name comes from Nickel Titanium Naval Ordnance Laboratory, where it was discovered in 1959.

Answer: Rapid cooling during manufacture put it under stress: the slightest crack releases all that energy. The glass is heated then cooled very fast on the surface: the skin sets in compression while the core stays in tension. It becomes several times stronger, but once broken it breaks entirely into small rounded granules. It is used for shower doors and car side windows.

Answer: Its pores are too small for a water drop but big enough for vapour. The stretched-PTFE membrane has billions of pores per square centimetre, about 20,000 times smaller than a raindrop but hundreds of times larger than a water vapour molecule. It was invented by Bob Gore in 1969 by suddenly stretching heated PTFE.

Answer: Nearly a metre in a single day. Bamboo is a giant grass, not a tree. Its shoots emerge from the ground already at their final diameter and lengthen at record speed. Strong in tension and light, it is used for scaffolding in Asia, and researchers see it as a sustainable alternative to some materials.

Answer: Pyrex. Thanks to added boron oxide, this glass expands very little with heat: it can go from a hot oven to a worktop without cracking. It is also used for laboratory glassware. Beware: some dishes sold under that name today are made of ordinary toughened glass, which is less tolerant.

Answer: It forms a hard ball under pressure, then runs through your fingers as soon as you let go. Under strong pressure the starch grains jam and the mixture behaves like a solid. As soon as the stress stops, water lubricates them again and it all turns liquid. It is a classic kitchen-science experiment, easy to do with cornflour.

Answer: Lighter for the same stiffness and corrosion-proof, it reduces fuel consumption. More than half of these aircraft's structure is composite. The weight saving brings significant fuel savings. The material also tolerates a more humid, more pressurised cabin, improving passenger comfort on long flights.

Answer: Dormant bacteria wake up when water seeps in and produce limestone that seals the crack. The spores, mixed into the concrete with their 'food', can survive for years. When a hairline crack lets water in, they reactivate and produce calcium carbonate. This spontaneous repair could extend structures' lifespan and reduce maintenance.

Answer: They char on the surface, and this layer protects the core, which keeps its strength for a long time. A massive beam burns slowly and predictably, at less than a millimetre a minute. A steel beam, by contrast, can suddenly lose strength at high temperature and buckle. Engineers therefore size timber with a 'sacrificial layer' in mind.

Answer: The porous oxide layer absorbs a dye, then it is sealed. Anodising electrically thickens aluminium's natural oxide layer. This hard, corrosion-resistant layer is at first riddled with tiny pores. Dyes are worked into them, then the pores are sealed, trapping the colour in the metal's surface itself.

Answer: Wilhelm Barthlott. In the 1970s Barthlott noticed that the cleanest leaves weren't smooth but covered in tiny waxy bumps. He patented the principle in the 1990s, leading to self-cleaning façade paints. The lotus leaf, a symbol of purity in Asia, is the most famous example.