pneumatic artificial muscle / soft actuator
A pneumatic artificial muscle is a soft, inflatable actuator that shortens and pulls when you fill it with air — much like a real muscle tensing. The classic design, the McKibben muscle, is a rubber tube wrapped in a woven braided sleeve. Pump air in and the tube bulges fatter; the braid, unable to stretch sideways without getting shorter, forces the whole thing to contract along its length and tug on whatever it is attached to.
Unlike a rigid motor or piston, it has no hard gears or moving metal parts — it is squishy, light, and naturally compliant, giving softly when squeezed, just like flesh. That makes it a favourite of soft robotics, where machines are built from rubber and fabric to grip fragile objects, bend around obstacles, or sit safely against a human body. Many wearable assist suits and gentle grippers are powered this way.
The trade-offs echo a muscle's: it can only pull, not push, so muscles are often used in opposing pairs (one contracts while the other relaxes), and its soft, air-driven nature makes exact, repeatable positioning harder than with a precise motor. What you gain is safety, lightness, and a forgiving touch that rigid machinery struggles to match.
A soft robotic glove uses air-muscle fingers that gently curl to help a stroke patient close their hand around a cup, then relax to let go — strong enough to grip, soft enough never to hurt.
Inflate to contract — a muscle-like pull built from rubber and braid.
Like a real muscle, it can only contract, never extend — so pairs are arranged to pull against each other, one undoing what the other does.