DW: Not only animals, but also plants are an inspiration for scientists. Professor Neinhuis, what can you actually learn from a cactus besides that it is prickly?
Christoph Neinhuis: There are different things that you can learn from a cactus. What interests us is: if you look at a regular tree, the side branches increase in diameter towards the stem to cope with the load. If you look at a cactus, the side branches have the smallest diameter exactly at the branch. You would expect them to break easily – but they don't. And that is a surprising thing for us.
If an engineer actually constructed like that, you would probably say, 'hey pretty bad job'?
A student would probably fail in his exam, if he constructed a junction like that. So the question we asked was why does a cactus do it like this? What is the special construction and how can we learn something from it?
What did you find out? What is so special about the cactus?
The special thing is how the branch is connected to the stem. And this fiber arrangement is what we studied. We tried to copy a light-weight carbon-fiber structure like this. This has been braided on a big machine with a robot arm. In one complicated process we've made a branched, light-weight carbon fiber composite material.
How long did it take to arrange that?
This is actually a process that took several years of interacting between biology and engineering. We had to transfer the process and the principle of the branch of the cactus into a carbon-fiber, composite material.
Nature is only working through trial and error. How come nature and evolution is more creative than engineers?
I wouldn't put it like this. Nature often has, because of limitations of the individual species, the need to look for unusual solutions for problems, especially under extreme conditions like a cactus. This is what we are looking for and we think that for the future we might find quite interesting adaptations which are also relevant for engineering.
About 20 years ago, researchers were quite euphoric about bionics. But then besides the water-repellant surfaces, nothing really came out?
One of the most spectactular, probably most successful stories is velcro. It is a bionic development and it is used everywhere in the world. Also optimization processes, used to shape structures, are quite common. Every car has a bionically-optimized structure in it. But noboby speaks about it.
What is the next step to come. What is the most important field in bionics?
I think the most important thing will be molecular bionics. How we can mimic the process of building together small molecules to increasingly complex structures - how nature does it. I think that is the future.
(Interview: Ingolf Baur)