For members who like to go out in the wet
Next time you pass through a pine forest spare a thought for the not so humble pine cone.
It may hold the key secret to a fabric which could change its breathability depending upon your temperature and sweat rate. Research has shown that the scales of the cone bend when wet due to bundles of fibre “cables” within an outer shell and having different rates of hygroscopic expansion function like a bi-metallic strip. “The difference lies in the way the cells are constructed. The fibre cables are composite tubes in which stiff cellulose microfibrils are wound around a core. The angle at which they are wound is the key. If the winding angle is changed the amount of water they absorb is changed. It should be possible to mimic the pine cone by making an artificial fibre in which two different fibres having different rates of hygroscopic expansion are co-extruded. If the temperature changed the fibre would bend like a bi-metallic strip, thus clothing made from these fibres would change its breathability.” The research did not say whether you will bend left, right, forward, back or sway gently in circular motion.
Found by Alan Linford in Professional Engineering, 15th October, 1997.