Picture this scenario: two hours after a bridge is destroyed in an earthquake, its replacement arrives in a crate. Thousands of handball-sized spheres roll out, spilling over one another in their haste to reach the river’s edge.
The first spheres pop into cube shapes and lock together to make a platform. Other blocks arrive, assembling into a staircase, while yet more form columns to buttress it from below. The self-building bridge stretches across the water.
Skyscrapers and passenger jets are engineering marvels made of billions of individual parts, yet they are dwarfed in complexity by the smallest living organism, which may have trillions of parts.
The secret of nature’s construction prowess is self-assembly – the ability of each individual component to organise itself into position for the good of the whole. Inspired by nature, a new generation of engineers are creating swarms of robots, able to assemble themselves into myriad different forms.
Harvard University has its Kilobot, a 1,000-strong swarm of 3-centimetre-tall robots that shuffle along on vibrating legs. Give these bots a pattern and they can coordinate like a cheerleading squad to display the desired shape – but only in two dimensions; and they just form pretty patterns rather than useful structures.
Massachusetts Institute of Technology has developed M-Blocks, little cubes that can leap up on one another to make basic 3-D structures. Inside each block is a motor that revs up a flywheel to 20,000 revolutions per minute, generating a store of energy. Braking the flywheel releases that pent-up energy and the brick hops forward like a wayward cricket – it works, though it’s not well controlled.
Now a team at the Architectural Association’s Design Research Laboratory in London has created the most sophisticated self-assembling system yet: the HyperCell.
These shape-shifting cells start out as a 10-centimetre cube but can morph their elastic skin into a sphere using six internal pistons. By shifting an internal weight, the ball can roll in any direction, like the spherical-bodied BB-8 droid from Star Wars: The Force Awakens.
What’s more, these cells are smart. Each cell contains a tiny computer chip. It can sense its environment and avoid obstacles. The cells can even communicate with each other – vital when working together.
The cells use magnets to join up. Rotating its internal magnets allows a HyperCell to climb on top of its colleagues until it finds the right position, then lock into place.
There is no top-down management system telling the cells what to do. Instead, they operate according to the hive mind principle. Give a group of HyperCells a task, and each individual cell decides how it can best help achieve the global aim – like a team of bees or a colony of termites.
The inventors have grand plans for their smart bricks: to redefine what a building is. “[Indoor] space today is usually used for various activities, but while the activities change, the space itself is the same,” says Pavlina Vardoulaki, architect, designer and member of the HyperCell team. She envisions a new form of “living architecture” – buildings that evolve to suit the wishes of their occupants.
The first applications, though, are likely to be in disaster relief. HyperCells could help erect temporary shelters, scaffolding to hold up teetering buildings, or even bridges to bring people to safety.
So far, the team has built about 40 prototypes, and the HyperCells can only support about 100 kg. The challenge will be manufacturing stronger HyperCells, with a price tag low enough to be practical, given that hundreds or even thousands of cells are needed for a basic structure.
But in the cells’ favour, they’re reusable – and could, at the end of a mission, disassemble on demand and even pack themselves neatly back into their crate.
Power comes from a flexible polymer solar cell embedded in the shell, while an internal battery stores charge.
Internal electromagnets can rotate within the core to face another HyperCell and lock on. Further rotations of the magnet allow a HyperCell to climb a stack of its neighbours.
The steel core is equipped with six hydraulic linear actuators – the struts that pop out to change the shape of the skin, each taking up to a 100-kilogram force.
The 3-D printed skin can morph from spherical to cube shapes, while rigid external panels give structure and support.
See HyperCells in action below.
Cathal O'Connell is a science writer based in Melbourne.
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