Research currently underway at MIT’s Distributed Robotic Laboratory (DRL) could lead to an innovative replicative manufacturing technique with the disruptive potential equal to that of 3D printing. Imagine a sand-like material that could autonomously assemble itself into a replica of any object encased within. Incredible though this may sound, the DRL researchers have already managed to build a large scale proof-of-concept, with 10-mm cubes acting as the grains.

Before we go into how these cubes – or “smart pebbles” – work, let’s sketch out the general concept. The idea is to create objects using a subtractive method, where excess material is removed just like when carving in stone. Each grain of smart sand would be a self-contained micro computer. These tiny machines would use an elaborate algorithm to communicate with the neighboring particles in order to establish the exact position and shape of the input object so that it can be replicated.

The already mentioned smart pebbles demonstrate this principle in a more easily understandable 2D setting. First the pebbles establish which of them border on the perimeter of the object to be replicated. Once identified, these particles pass on a message to their neighbors, and effectively specific particles selected by the algorithm are notified that an identical (or scaled) arrangement should be recreated a safe distance away, so that the two shapes do not overlap.

Once the perimeter of the copy is identified, the pebbles within that area bond to each other, while the redundant material simply falls away. The resultant object would be solid, but it could be easily deconstructed simply by putting it back into the heap of smart sand. The constituent grains would detach from each other and the whole process could be repeated with an entirely new shape.

Each smart pebble cube used for testing was equipped with a set of electro-permanent magnets on four sides. The magnetic properties of such magnets can be switched on and off using electrical impulses, but unlike electromagnets, they do not require electricity to sustain these properties over time. With each particle neighboring on eight other particles in a 2D scenario, the magnets allow for selective bonding with any of the neighbors. However, the magnets also play a role in communication and power sharing.

Each smart pebble was also fitted with a rudimentary microprocessor capable of storing 32 kilobytes of code and boasting two kilobytes of working memory. With such limited processing power at the disposal of a single unit, the main computational heft had to fall on the distributed intelligence algorithm that constitutes the core of the current DRL endeavors.

“How do you develop efficient algorithms that do not waste any information at the level of communication and at the level of storage?” asks Daniela Rus, a computer science and engineering professor at MIT. The answer to that question is likely to be found in a paper that Rus co-authored with her student, Kyle Gilpin, and which is going to be presented in May at the IEEE International Conference on Robotics and Automation.

The algorithms developed at DRL have already been shown to work robustly with 3D scenarios, where the bed of smart sand would be divided into layers, each constituting a separate 2D grid. Now the only thing that stops smart sand from joining 3D printing in revolutionizing the world of rapid manufacturing is getting the scale right.

But according to Robert Wood, an associate professor of electrical engineering at Harvard University, this is not an issue. Wood reckons recreating the functionalities of the smart pebbles in smaller scale is feasible. Yes, it would require quite a lot of engineering, but the goal is well defined and reachable. “That’s a well-posed but very difficult set of engineering challenges that they could continue to address in the future.”, he says. If Wood is right, the future of subtractive manufacturing is bright.

Watch the video below to find out more about the algorithm behind smart pebbles.

Source: MIT

Sourced & published by Henry Sapiecha


Wouldn’t your latest generation tablet be way cooler if it ran on live crabs? Thanks to Yukio-Pegio Gunji and his team at Japan’s Kobe University, the era of crab computing is upon us … well, sort of. The scientists have exploited the natural behavior of soldier crabs to design and build logic gates – the most basic components of an analogue computer. They may not be as compact as more conventional computers, but crab computers are certainly much more fun to watch.

Electricity and microcircuits aren’t the only way to build a computer. In fact, electronic computers are a relatively recent invention. The first true computers of the 19th and early 20th centuries were built out of gears and cams and over the years many other computers have forsaken electronics for marbles, air, water, DNA molecules and even slime mold to crunch numbers. Compared to the slime mold, though, making a computer out of live crabs seems downright conservative.

The scientists at Kobe university didn’t just pop down to the market for their crabs. They focused their attention on a particular species: soldier crabs (Mictyris longicarpus). These are found in on the beaches of Australia and surrounding islands where they regularly provide visitors with surreal performances. Individually, the soldier crabs are timid little blue crustaceans that won’t even go into the water, but when they form into swarms, which can number in the tens of thousands, it’s a different matter.

Once set in motion by something like a bird’s shadow passing overhead, the soldier crabs tear off like an army of demented robots. They rush about in a strange, boiling mass that seem like exercises in utter chaos, yet the swarm itself moves in a remarkably consistent straight line. This determined, predictable manner of movement is the key to the crab computer.

When two swarms of soldier crabs collide something remarkable happens. Instead of collapsing into a riotous battle, the two swarms meet in a manner that’s as predictable as a pair of billiard balls hitting each other. When two identical billiard balls collide head on they, ideally and all things being equal, rebound off one another in the opposite direction. If they strike at an angle, they fly away from each other at the opposite angle. It’s all very predictable Newtonian mechanics. In the case of soldier crabs it’s like two balls of soft modelling clay hitting each other. They squash together at the new, larger swarm and head off at the combined angle of the original swarms with a remarkable degree of predictability.

Exploiting this behavior, the Kobe team figured out how to use the crabs to make logic gates. They did this by placing two swarms of crabs in a simple maze. In one configuration, the swarms were set off in two legs of the maze. When they collide, they head off down a third leg. Since the swarms always go in the same direction, if only one swarm is placed in the maze, it will always go down the same output leg as if it had collided with the other swarm and not double back up the other leg. In this way, the maze becomes an OR gate. If one or two swarms enter the maze, the output is always positive. One swarm OR another swarm in the maze equals a positive, otherwise negative.

The researchers also used another maze was in the shape of an X with a fifth vertical leg stuck running up from the center. In this maze, letting loose one swarm resulted in the swarm passing straight through the center and into the opposite leg of the X. If two two swarms are loosed, they collide in the center, sending them up through the center leg. This is the crab equivalent of an AND gate. One swarm going in provides a negative. Two provides a positive. One swarm AND another swarm equals positive, otherwise negative.

With these two gates, it would be theoretically possible to build more complicated logic gates and from there, full-fledged computers.

Currently, there are no plans to build a full-blown crab computer, but if seafood cybernetics ever does take off, this, they will say, it where it all began.

The research was recently outlined in a paper entitled

Robust Soldier Crab Ball Gate [PDF] in the journal Complex Systems

Sourced & published by Henry Sapiecha