IEEE Robotics & Automation Magazine - September 2015 - 129

thermoplastics actuated by a combination of cables and motors. Many more fingered or handed grippers used active soft
matter, such as electroactive polymers (EAPs) [21], shapememory polymers, or hydrogels [22], which can self-actuate
with energy sources from electrical current, temperature
change, hydration, or even visible light. These grippers have
mainly served as proof of concept that bending of some soft
matter could be used in robotics, and none of the case studies
has described how the soft-matter-based grippers surpass the
capabilities of existing grippers.
Figure 4 shows how bending of soft matter could generate legged and crawling locomotion. Elastomers, thermoplastics, and polymer gels have been used. From the
perspective of the actuation method, elastomers may be actuated by cables and motors [Figure 4(a)], or valves and air
pumps [Figure 4(b)], or even biological material cardiomyocytes [Figure  4(e)]; thermoplastics may be actuated by cables and motors [Figure 4(c)] or shape-memory alloys
[Figure 4(d)]; and EAP gel is self-actuated to electrical

stimuli [Figure 4(f) and (g)]. From the perspective of gait
pattern, using the elastic energy from bending from the rear
of the body and asymmetric friction between
The common feature of
the front and the rear of
the body is the most
these grippers is that their
common way to achieve
forward movement [Figgripping and releasing
ure 4(a), (e), and (g)]. Alternatively, quadrupedal
fully relies on the bending
and bipedal walking
could be achieved by
of the entire finger(s),
bending of the leg(s)
from different sides of a
hand, or arm.
robot [Figure 4(c) and
(d)]. With networked
chambers of siliconebased elastomer, a robot could select chambers in the body
to bend and achieve multiple gait patterns, such as walking,

Servomotor

0 kV

3.0 kV

Tendon TPA Arm

0 kV
(a)

(b)

(c)
Ethanol

Water
(d)

(e)

(f)

.050 in

.050 in

(g)

(h)

Figure 3. The bending of polymers for fingered gripping in soft-matter robots: (a) polyethylene terephthalate layered with prestretched
dieletric elastomer actuators as a hand [52], (b) EAPs directly used as fingers [21], (c) an ethylene vinyl acetate (EVA)-based thermoplastic
adhesive (TPA) finger actuated by cables and a servo motor (work by Liyu Wang and Fumiya Iida), (d) networked chambers of siliconebased elastomer powered by an air pump as a hand [20], (e) water-sensitive polyelectrolyte hydrogel with asymmetrically distributed
cupric ions in ethanol used as a hand [53], (f) silicone-based elastomer actuated by shape-memory alloys for grasping [14], (g) bilayers of
temperature-sensitive N-isopropylacrylamide gel and acrylamide gel as fingers [22], and (h) temperature-sensitive shape-memory polymer
actuators directly used as an umbrella-shaped interventional ischemic stroke device [54].
September 2015

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IEEE ROBOTICS & AUTOMATION MAGAZINE

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Table of Contents for the Digital Edition of IEEE Robotics & Automation Magazine - September 2015
