Tag Archives: bio-mimicry

Technica

Plastic, Heal Thyself!

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Blood is a remarkable substance: it transports vital oxygen to nourish our cells, it carries signalling chemicals that control our actions, it delivers armies of substances, at a moment’s notice, to ward against bodily infection and injury. Now, imagine a similar, bio-mimetic process in plastic, which remarkably allows a plastic material to heal itself.

From New Scientist:

If you prick it, does it not bleed? Puncture this plastic and it will heal itself with oozing fluids, in a process that mimics the way blot clots form to repair wounds. The plastic could one day be used to automatically patch holes in distant spacecraft or repair fighter jets on the fly.

So far, efforts to develop materials that fix themselves the way biological tissue mends itself have been limited. Scott White at the University of Illinois at Urbana-Champaign and his colleagues developed one of the first versions in 2001, but that material could only heal microscopic cracks.

Now his team have created a plastic lined with a type of artificial vascular system that can heal damage large enough to be visible to the naked eye.

The key is a pair of liquids that react when they are mixed. One fluid contains long, thin molecules and the other contains three-sided molecules. When the fluids mix, the molecules join together to create a scaffold, similar to the way blood platelets and fibrin proteins join to form a clot.

After a few minutes of contact, the liquids turn into a thick gel that fills the damaged area. Over a few hours, other ingredients within the fluids cause the gel to harden.

Strength from weakness

To test the concept, the team ran separate channels of each liquid through a plastic square and punctured it, creating a 4-millimetre hole with 35 millimetres of surrounding cracks. This also tore open the fluid channels.

Pumps on the edge of the plastic square squirted the fluids into the channels, where they oozed out and mixed, filling the hole and the radiating cracks within 20 minutes. The material hardened in about 3 hours, and the resulting patch was around 60 per cent as strong as the original plastic.

Holes larger than 8 millimetres proved more difficult to fill, as gravity caused the gel to sag before it could harden. The team thinks using foams in place of fluids would fill larger gaps, but they haven’t tested that idea yet.

Eventually, White and his team envision plastics with multiple criss-crossing channels, to ensure that the fluids always overlap with a damaged area. Embedding this synthetic vascular network would weaken the original material, but not by much, they say.

“You pay the price for being able to repair this damage, but it is certainly one that nature has figured out how to tolerate,” says team member Jeff Moore, also at the University of Illinois. “If you just look to things like bone or trees, they are all vascularised.”

Read the entire article here.

Image: Self-healing materials fix large-scale damage. Courtesy of University of Illinois at Urbana-Champaign.

BigBang

Biological Gears

We humans think they’re so smart. After all, we’ve invented, designed, built and continuously re-defined our surroundings. But, if we look closely at nature’s wonderful inventions we’ll find that it more often than not beat us to it. Now biologists have found insects with working gears.

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From New Scientist:

For a disconcerting experience, consider how mechanical you are. Humans may be conscious beings with higher feelings, but really we’re just fancy machines with joints, motors, valves, and a whole lot of plumbing.

All animals are the same. Hundreds of gizmos have evolved in nature, many of which our engineers merely reinvented. Nature had rotating axles billions of years ago, in the shape of bacterial flagella. And weevil legs beat us to the screw-and-nut mechanism.

The insect Issus coleoptratus is another animal with an unexpected bit of machinery hidden in its body. Its larvae are the first animals known to have interlocking gears, just like in the gearbox of a car.

In high gear

I. coleoptratus is a type of planthoppers – a group of insects known for their prodigious jumping. It takes off in just 2 milliseconds, and moves at 3.9 metres per second. “This is a phenomenal performance,” says Malcolm Burrows of the University of Cambridge. “How on earth do they do it?”

Burrows first ran into the larvae of I. coleoptratus in a colleague’s garden. “We were poking around and there were these bugs, jumping around like crazy.” He took a closer look, and noticed that each larva had meshing gears connecting its two hind legs. The gears had been seen before, by a German biologist called K. Sander, but his 1957 paper isn’t even on the internet.

The bulb at the top of each hind leg has 10 to 12 teeth, each between 15 and 30 micrometres long. Effectively, each hind leg is topped by a biological cog, allowing the pair to interlock, and move in unison.

Working with Gregory Sutton of the University of Bristol, UK, Burrows filmed the gears at 5000 frames per second and confirmed that they mesh with each other (see video, top).

Great timing

The two hind legs moved within 30 microseconds of each other during a jump. Burrows and Sutton suspect that the gears evolved because they can synchronise the leg movements better and faster than neurons can.

Other animals have gears, but not gears that mesh, says Chris Lyal of the Natural History Museum in London. “When you look at [I. coleoptratus‘s gears], you wonder, why can’t anything else do that?” he says.

The German study from 1957 claims that all 2000-odd planthoppers have gears. “I’ve looked at about half a dozen, and they all have them,” says Burrows. “I’d be hesitant to say no other animal has them,” says Burrows. “But they haven’t been described.”

Read the entire article here.

Video courtesy of New Scientist.