A collection of known methods to achieve multiple degrees of freedom with soft actuators.
Kevin C. Galloway has created a multi-DOF bending soft actuator made out of “three independent fiber-reinforced, tube-shaped, linear actuators”.
Already in 1989, the lab of Koichi Suzumori in Tokyo have created an FMA - Flexible Microactuator that operates in 7 degrees of freedom. It is made from 3 separate air chambers and one whole fiber reinforcement.
The Swiss Reconfigurable Robotics Lab - EPFL have designed a 2-DOF soft actuator that uses an adjustable stiffness layer. The layer uses two smart memory polymers in each side, that become stiff when heated.
The lab at harvard had produced a multi-multimodule manipulator with a controllable stiffness, a bio-design inspired by the octopus.
Matthew Borgatti created a trefoil tentacle with powder printed molds. The instructions are found on thingiverse.