The idea of “soft robots”—robotic components that don’t comprise rigid parts—has been around for a while, but now researchers in Switzerland believe they may have come up with a combination of components that will allow soft robot technology to be more widely applied to a range of uses, including physical rehabilitation.

The soft robots developed in the Reconfigurable Robotics Laboratory (RRL) look like a sausage hooked to pressurized air pump, and are basically akin to balloons whose expansion and contraction can be finely controlled—both in terms of direction and force. They’re known as soft pneumatic actuators (SPAs).

And while that concept may seem simple enough, things quickly get complicated: the materials used for the SPAs have to be rigid enough to withstand significant air pressure without distorting their shape, yet pliant enough to bend and stretch in muscle-like fashion; they need to be light; and they need to be sensitive to both quick blasts of air for strong movement and weaker blasts for more delicate, slower motion. Perhaps most important of all for researchers, the SPAs need to be predictable, so that computer modeling can guide development.

Writing in the journal Scientific Reports, the RRL researchers believe they may have hit on the right combination of materials, a 2-part arrangement of plastic materials consisting of a pliant actuator body and a rigid shell that guides the type of motion required—think along the lines of a caterpillar wearing a corset. The resulting SPAs are capable of bending up to 200 degrees or stretching to 6 times uninflated length, depending on the model. The materials also allow for reliable computer modeling—so much so that RRL has published open-source online software that allows anyone to investigate various configurations of bodies and shells.

After developing a workable technology, the RRL team began collaborating with physical therapists in Switzerland to develop a prototype belt that could help individuals poststroke as part of gait rehabilitation. The prototype, included in a video from RRL, uses SPAs that lengthen and contract to help create stability in the lower torso and hips.

Researchers admit that while their findings are moving soft robot technology forward, the concept has a long way to go—at least when it comes to physical rehabilitation. Right now, the SPAs are controlled by a series of bulky pneumatic pumps, and researchers are looking for ways to create miniaturized, wearable devices to power the SPAs.

Research-related stories featured in PT in Motion News are intended to highlight a topic of interest only and do not constitute an endorsement by APTA. For synthesized research and evidence-based practice information, visit the association's PTNow website.