Because there is no all-embracing basic theory of biology in the way that there is with chemistry and physics, biologists have to watch carefully and observe. It’s not just the watching; it’s allowing the observations to generate patterns. Our brains are specialised to extract patterns from what we see, hear and feel, and use those patterns to predict what might happen next. It’s probably why so many people like Agatha Christie novels, crosswords, poker or music. They allow us to play with pattern and prediction in a safe environment (except for poker . . . ) and so hone our skills in an important part of our survival strategy – who or what will attack next, and from what direction? When should I plant the oats / barley / root crops? The incoming information is compressed, generalised, and feeds analogies. The analogies feed our experience and skills. They are our education.
Biologists should be good at analogies. They have trained themselves to observe a complex world in need of simplification in the cause of understanding. I’m a biologist. I love solving problems. I also have some skills in engineering. My analogies roam everywhere, especially on the seashore. Rock pools are a marvellous incubator for invention.
Let’s take a starfish as an example. Like its close relatives, sea urchins, it has a bony shell-like skin through which poke large numbers of hydraulic tube feet. When you’re down on the beach this summer, turn a starfish over in a rock pool and you’ll see lots of these feet, several millimetres long, waving around, apparently aimless.
If you leave the starfish long enough, it will curve the tip of one arm round so that its tube feet can attach to the underlying rock of the pool, and pull itself back to its normal position. But try dropping a small piece of food (a winkle taken out of its shell, for instance) onto the tube feet, and you’ll see them convey the food to the mouth, which is in the middle of the area where the arms meet. Now drop a tiny stone, or the ex-winkle’s shell, onto the tube feet and they reject it, casting it to one side. Can the tube feet distinguish between food and shell dropped next to each other?
These and other observations suggest the concept of a two-dimensional conveyor. With embedded sensors this could be used to sort, dismantle or assemble objects. The surface of the conveyor could be made of starfish-like tube feet using composite hydrogels (but possible only under water and a bit slow); or cylindrical rollers as used in airports for loading cargo into the hold of aircraft; or spherical rollers like computer trackballs; or segments of carpet with the nap pointing in different directions (four segments in a unit with the nap mutually orthogonal – vibrating the segments in different patterns to make an object move in the desired direction). The objects have to be labelled – RFID possibly. Or sorted by weight. Sensors embedded in the conveyor units respond individually under computer control.
It’s a Sorting, Transporting And Re-configurable conveyor.
A brief study showed that the STAR conveyor takes up much less space than an array of unidirectional conveyors and is far more adaptable. Adding an extra sorting stream requires an extra conveyor belt in a unidirectional system, but needs only a change to the sorting and directions of transport across the STAR conveyor – which can be done very quickly from computer control and requires no extra information. The items to be sorted know where they have to go.
This article first appeared in Professional Engineering 2002, No 4