杏吧原创

It鈥檚 a rather unpleasant problem. A robot that powers itself by converting a foul broth of urine, sewage sludge, dead insects and rotten vegetables into electricity keeps getting its fuel pump jammed by the chunkier lumps. Now the problem has been solved by replacing the pump with a 3D-printed, shape-shifting analogue of the mammalian heart.

At issue is the fuel supply for Ecobot 鈥� which is a test platform for self-powered autonomous machines. Researchers at the Bristol Robotics Lab (BRL) in the UK hope that such robots will one day be able to work continuously in dangerous or polluted areas because they seek out their own energy supplies and so need little tending by humans.

Once it has found a fuel source 鈥� urine-rich wastewater in a sewer, say 鈥� Ecobot needs to pump it into a biochemical reactor called a microbial fuel cell. This breaks down organic matter in a way that liberates electrons to produce electricity and charges the robot鈥檚 batteries. Indeed, the lab recently demonstrated the concept by using urine to charge a mobile phone (see video, above).

But the Ecobot鈥檚 conventional electric-motor-driven pump was prone to blockages and breaking down. 鈥淪o we鈥檝e used smart materials that contract a bit like muscles do to compress the body of a far simpler pump,鈥� says engineer Peter Walters of the Centre for Fine Print Research, also in Bristol, who worked on the pump design with BRL鈥檚 lead Ecobot engineer Ioannis Ieropoulos.

Sludgy deposits

They designed an acrylic chamber shaped like a mammalian heart with soft, compressible silicone bellows mounted above it. Using artificial muscles 鈥� based on nickel-titanium fibres 鈥� on either side, the bellows push up and down creating a heart-like pumping motion when a current is applied. 鈥淚t pumps enough fuel for the metabolism of the microbial fuel-cell stack without getting blocked,鈥� says Walters.

One problem urine and sewage sludge creates is that it deposits a phosphorous and ammonia-rich rock-like scale 鈥� called struvite 鈥� in pumps and pipes. 鈥淥ur pump leaves struvite in the bottom rather than blocking flow,鈥� he says.

But this is not a miracle fix: the prototype shape-shifting pump is one seventh as efficient as the motor-driven pump. But at least it doesn鈥檛 block up so easily. 鈥淭his has proved the concept. We now have to improve its efficiency,鈥� says Walters.

That will be tough though, says Darwin Caldwell, an engineer at the Italian Institute of Technology in Genoa, who works on humanoid robots. 鈥淐onceptually, light, flexible shape-memory actuators are very interesting 鈥� particularly for making small, flexible pumps. But their efficiency has never been demonstrated to be high in any application. That does not mean they cannot be improved, but it won鈥檛 be an easy task.鈥�

One option, he says, might be to use an arrangement of motors to pump the heart instead.

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