Extract from Chapter 2:
The Great Sacred Lotus Cleans Up
Some of the ongoing Lotus-Effect research has a playful quality in keeping with the purity of this blindingly simple idea. In 2001, two French researchers came up with a Zen-like party trick by coating drops of water so that they can roll on glass without breaking up, or even float on water itself. These ‘liquid marbles’ are made with lycopodium grains coated with a silicone. This creates a lotus-like surface with almost perfect water repellency: hence their spherical shape and ability to float on water. This ‘non-stick water’ may eventually find applications in the packaging and delivery of fluids, but for now it induces a Buddha-like smile at the quirkiness and eternally surprising nature of the physical world.
As usual, when we think we’ve invented something really far-out, nature seems to have got there first. There are aphids that, in an examples of the crazily degraded lifestyles that are so common in the natural world, live all their lives inside plant galls. In fact, the galls – those warty lumps found on the undersides of tree leaves, especially on oaks – are created by the aphids, which interfere with the host plant’s metabolism, thus creating the galls. In choosing, in evolutionary terms, to live like this, these aphids have created a problem for themselves. Aphids feed on the sap of plants and they produce large quantities of a whitish, sugary excrement known as honeydew. Aphids that live on the surface of plants have developed a symbiotic relationship with ants, who feed on the honeydew and protect the aphids. But gall-living aphids have no such means of disposal: they risk drowning in their own excrement unless they can easily evacuate it from the gall. The honeydew is very sticky and once an aphid gets trapped in a ball of honeydew it can’t escape.
To the rescue comes super-non-wettability of an ingenious kind. The aphids produce needles that break off and line the inside of the gall with a rough waxy coating. The drops of honeydew are coated with the wax and become non-wetting honeydew parcels just like the water marbles. There is even a caste of soldier aphids whose job it is to elbow the parcelled-up honeydew balls out of the gall!
The aphid’s secret was revealed in a paper, wittily entitled ‘How aphids lose their marbles’, by the young Indian physicist L Mahadevan and his team. Mahadevan, at Cambridge University when he did this work and now at Harvard, is one of the most dazzling figures in bio-inspiration. He is a mathematical physicist who works with biologists to unravel bio-inspired problems right across the spectrum. His papers have artistic references wherever possible, rigorous mathematics and, above all, they impart a sense of the remarkable creativity, chutzpah even, of nature in devising these solutions.
When I visited Mahadevan at Harvard, his computer desktop was a treasure trove of biological curiosities, involving origami, the draping patterns of clothes, biological springs and ratchets, and those aphids that lose their marbles. Mahadevan has a short attention span, which means that he attacks these problems in a brilliant mercurial way and then passes on to the next. He is a delighted roamer in this new terrain of bio-inspiration, throwing out brilliant suggestions that others can follow up.
So we see that the Lotus-Effect is not just a matter of building maintenance. It sheds light on many strange corners of the natural world as well as adding some radiance to the built environment. Just as the self-cleaning properties of the sacred lotus were of philosophical, spiritual and artistic importance to eastern civilizations, the idea of self-cleaning can be a secular boon to the northern latitudes. In The Poetics of Space, the French philosopher Gaston Bachelard has suggested that cleaning might itself have spiritual/aesthetic value:
And so, when a poet rubs a piece of furniture – even vicariously – when he puts a little fragrant wax on his table with the woollen cloth that lends warmth to everything that it touches, he creates a new object; he increases the object’s human dignity; he registers the object officially as a member of the human household.