Page 358 - Control Theory in Biomedical Engineering

324 Control theory in biomedical engineering

achieve jamming due to the contact force between the auxetic material and
the restrictive material. A two-layered tubular system can be designed where
the outer layer has fixed dimensions and is semirigid (i.e., it is only allowed to
bend). The inner tube is made of an auxetic material, which expands upon
elongation. However, since the available space is restricted, the inner tube
will jam against the outer tube, creating friction which resists further motion.
The mechanism and proposed design are shown in Figs. 4 and 5.

Outer tube Jamming at the boundary
Auxetic material (after expansion)

Tensile load
Auxetic material (before expansion)

Material expands
under tensile load

Fig. 4 Mechanism of jamming through auxetic materials.

Inner auxetic tube

Outer jamming tube
(A) (B)

Fig. 5 (A) CAD of the proposed assembly. (B) Example of an auxetic tube.