Soft robotic components can be safer for humans to interact with, have an ability to grasp different kinds of objects and better handle rough environments, but more malleable parts have their downsides too. What if there was a way to retain the benefits of stiffer materials while also tapping into the field's softer side? Scientists have developed a multipurpose fiber that changes its stiffness depending on temperature, making for a highly versatile wire that could one day be used in everything from folding drones to shapeshifting furniture.
The team at the École polytechnique fédérale de Lausanne's Laboratory of Intelligent Systems has been behind some impressive robotics advances over the years. Unmanned aircraft that use wings to walk on land, a grasshopper-like robot that can leap 27 times its body size and an award-winning crash-proof robot that flies inside a spherical cage are just a few examples.
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Its latest creation is a composite thread that is rigid in its natural state. At its core is a silicone tube that holds low melting point alloys inside, which remain solid at room temperature and give the fiber a stiff nature, much like a thin metal wire. But wrapped around the tube is a copper wire, and when an electrical current is passed up and down this wire it heats up the alloys inside.
When the temperature inside the tube ticks over 62 °C (143.6 °F), the alloys melt. This takes as little as ten seconds and makes the fiber up to 700 times softer, 400 times more deformable and able to be stretched up to four times its own length. Lab boss Dario Floreano describes the wire in this state like spaghetti and says it could be wrapped around objects, knitted into electronic casts for broken bones and even used in shapeshifting furniture.
An added benefit is that it has the capacity to self-heal. If the thread is cracked or snapped when in its solid state, the metal core can simply be melted, mended and you can start again.
The team is currently putting the fiber to work in a vehicle that uses the varying stiffness to morph from miniature aircraft into a robotic car. It does this by using the changing nature of the thread to switch its motors from a propellor position to a wheel position for rolling across land.
But it hopes that this is just the beginning and, while it imagines a whole raft of applications for the material, one where it sees particular potential is in the medical world. It could lead to endoscopes and other instruments that are soft and gentle enough when navigating delicate or sensitive regions of the body, but then firm up when they need to penetrate tougher tissue.
The team's research was published in the journal Advanced Materials.
You can hear from the researchers in the video below.