From a group of what seem to be mostly Italian scientists with the delightfully ominous name of The Octopus Project. Construction details were published as Design of a Biomimetic Robotic Octopus Arm in Bioinspiration & Biomimetics in 2009. A 2008 conference preprint is available here.
Fig. 1. (a) Arrangement of the hydrostatic muscles in the octopus tentacle: the longitudinal muscles (L) extend along the whole tentacle length; the transversal muscles (T) connect the external tissues and, when contracted, make the tentacle diameter reduce and the length increase. The external oblique muscles (O) around the whole tentacle allow torsion. The central axis of the arm is occupied by the axial nerve cord (N), which includes both nerve cell bodies and axons, and it is wrapped by medial oblique muscles. (b), (c), (d) Design of the muscular elements of the robotic tentacle: longitudinal muscles (b), transverse muscles (c), and integration in an arm (d).