Soft robots that mimic human muscles

Robots are expected to be rigid, fast and efficient. However, researchers at EPFL's Reconfigurable Robotics Lab (RRL) have created a predictive model that can be used to control the mechanical behaviour of a soft robots' various modules. The researchers have shown that their model could predict how a series of modules – composed of compartments and sandwiched chambers – moves. The cucumber-shaped actuators are said to stretch up to around five or six times their normal length and bend in two directions, depending on the model.

Soft robots are made of elastomers, including silicon and rubber, so they are inherently safe. They are controlled by changing the air pressure in 'soft balloons', which also serve as the robot's body.

"We conducted numerous simulations and developed a model for predicting how the actuators deform as a function of their shape, thickness and the materials they're made of," said researcher Gunjan Agarwal.

"Elastomer structures are resilient but difficult to control. We need to be able to predict how, and in which direction, they deform. And because these soft robots are easy to produce but difficult to model, our step-by-step design tools are now available online for roboticists and students."

Potential applications include patient rehabilitation, handling fragile objects, biomimetic systems and home care.

One of their designs is a belt made of several inflatable components, which holds patients upright during rehabilitation exercises and guides their movements. The belt's soft actuators are made of pink rubber and transparent fishing line. The placement of the fishing line guides the modules' deformation when air is injected.

"For now, the belt is hooked up to a system of external pumps. The next step will be to miniaturise this system and put it directly on the belt," explained project leader Matthew Robertson.

The researchers are also developing adaptable robots capable of navigating in cramped, hostile environments. And because they are completely soft, they should also be able to withstand squeezing and crushing.