Energy independence for sewage-eating robot

Paul Raven @ 22-07-2010

This story’s all over the place, at venues as diverse as Hack-A-Day and Mike Anissimov’s blog… and with good reason. Here’s the lede from PhysOrg:

UK researchers have developed an autonomous robot with an artificial gut that enables it to fuel itself by eating and excreting. The robot is the first bot powered by biomass to be demonstrated operating without assistance for several days. Being self-sustaining would enable robots of the future to function unaided for long periods.

Yup, you read that right – this machine eats a kind of organic slurry, digests the nutrients in it and then craps out the waste. Not quite so elegant (or do I mean sinister?) as the proposed rat-eating household bot we mentioned a while back, eh?

Joking aside, this is quite a big deal – energy-autonomous machines could do all sorts of amazing things, and some scary ones too. It also stirs up the same arguments about “artificial life” as the Venter announcement, albeit coming from a very different angle: if I remember my GCSE biology right, eating and excreting are two pillars of the scientific definition of biological life, and there’s a machine that does both as well as being capable of independent movement. Interesting times, people, interesting times.

Speaking of sewage and energy, we could probably be getting some of our household wattage from human waste, and there’s a pilot scheme for biomethane recapture from sewage here in the UK at the moment. But gas is tricky and dangerous to store and pipe – why not cut out the middle man and just get the energy out of the sewage directly? To be truthful, there’s still a middle man… billions of them, in fact. Apparently certain nanoparticle coatings applied to graphite anodes in sewage tanks encourage certain bacteria to proliferate, eating sewage and releasing electrons all the while. Your biowaste gets cleaned up, and you produce electricty at the same time! Sounds almost too good to be true… but they’ve got it working in a lab environment, so you never know.


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Paul Raven @ 09-07-2009

If you’ve been hankering for an intersection of nanomaterials and old spy movie cliches, today’s your day: a gang of researchers in Illinois reckon they’ve found a way to use nanoparticles to make messages that erase themselves after a certain amount of time.

A team at Northwestern University in Evanston, Illinois, coated gold nanoparticles with a layer of hair-like molecules called 4-(11-mercaptoundecanoxy)azobenzene or MUA. When zapped with ultraviolet light, these filaments change their shape and charge distribution, causing the nanoparticles to congregate together and change colour […]

To put this colour-changing ability to good use, the team dispersed the nanoparticles in a gel and sandwiched it between plastic sheets to produce a thin, red film. When Grzybowski and his colleagues shone UV light at the film, either through a patterned mask or using a UV pen, they found they could print a range of images or write words onto the film in just a few seconds.

The colour change is not permanent, however. In the absence of UV light, the MUA gradually reverts to its original shape, allowing the nanoparticles to disperse and the images to disappear.

Your mission, should you choose to accept it, is to work out how many times more expensive and complicated it would be to use this stuff instead of scribbling a note on some rice paper. Or whether the Etch-a-Sketch people will be tempted to build a 2.0 version.