Most soft actuators with multiple active degrees of freedom do not take advantage of the full extensibility of elastomer. Here we introduce a technique for better utilizing this extensibility for more versatile soft actuators. Embedded tendons that slide through channels within an inflatable, fiber-reinforced elastomer membrane enable active control of the membrane’s geometry at high elastomer stretches, bringing its functionality close to that of a natural hydrostatic skeleton. We demonstrate this using an initially planar, tendon-driven, fiber-reinforced membrane actuator with a single fluid cavity that can actively extend, contract, bend in multiple directions, and grasp when inflated. Most notably, the same membrane stretches to nearly three times its initial length directly along the path of a sliding tendon while performing these motions. Two such membranes are used on a robotic platform to walk with the gait of a velvet worm using a fixed mass of air, turn, climb a ramp, and navigate uneven terrain.
