Scientists have used artificial muscles in some capacity for more than a decade,
and still only have a basic understanding of the technology. A new study by a
team of university researchers has offered an explanation about why these
materials react in this way.
Robert B. Moore
These artificial muscles are ionic polymer metal composite (IPMC)
actuators, consisting of a thin polymer strip plated on both surfaces with
conducting metal and an attached charged component, which forms an open,
permeable structure that can be soaked with water molecules and oppositely
charged ions, according to a news release.
An electric charge across the metalized surfaces causes the strip to
flex in one direction; while an alternating charge will send it in the opposite
direction, like a fish’s tail.
The researchers, working in conjunction with the National Institute of
Standards and Technology at its Center for Neutron Research, used a neutron
imaging beam — which aided in mapping the locations of water molecules
— to watch an IPMC move and found that a hydraulics-like mechanism is a
major force in the actuator.
on of these materials as
substitutes for natural muscle tissue will undoubtedly result from
interdisciplinary efforts of researchers in science and engineering.”
Bringing this information from the abstract to the practical, it would
be difficult to move forward with future developments in this field without a
complete understanding of the foundation of this technology.
“Without a fundamental understanding of the molecular and
morphological origins of IPMC actuation, we will be severely limited in our
goals to someday discover and develop polymer-based materials that can replace
natural muscle tissue,” he said.
That understanding will help the technology progress beyond the
limitationscurrent hurdles researchers currently face, such as how to increase
the amount of force the EAPs produce during actuation.
“A principle limitation currently facing the IPMC field is that
these EAPs do not produce much force during actuation,” Moore said.
Current actuators can be small and light-weight, and they can flex over
relatively large distances, but since that generated force is so low, the
“muscles” are not very strong, according to a release.
Potential uses for this technology include microfluidic systems, where
they would function as pumps or valves, or as tiny robotic grippers in
applications where other actuators are impractical.
The ultimate goal, Moore said, is to discover and develop polymer-based
materials that will be able to replace natural muscle tissue. Force will be a
key component of that ability.
This technology also paves the way for another approach to
proprioception. By deforming an IPMC, researchers can create a measurable
charge on the film’s surface proportional to the extent of deformation.
This ability “could provide useful tactile sensors for artificial touch
and feeling,” he told O&P Business News.
“Through advancements in material design, morphological control,
and of course device engineering, the grand challenge of artificial muscles
meeting the application requirements of a human host should be realized, given
sufficient resources to facilitate interdisciplinary collaborative
research,” Moore said.
Next up for this area of research is broadening the scope of material
“With an understanding of the fundamentals, we can now explore the
new concept of ‘design of IPMCs’ to develop the next generation of
artificial muscles,” he said. “We must also learn how to effectively
couple the behavior of IPMCs with other classes of EAPs for engineered
performance and durability.” — by Stephanie Z. Pavlou
I have been somewhat amazed at how long there has been active research
on artificial muscle technology — first developed in its modern form in
Menlo Park, Calif. 20 years ago — and how many methods of powering
artificial muscle have been tried, some successfully, most unsuccessfully, but
This latest method utilizing water as a fuel as opposed to an electric
charge is reflective of a new trend in powering these devices that mimics our
own circulatory system. Utilizing this approach, the development of artificial
limbs is closer than ever before to becoming anthropomorphic in not only its
function, but in its structure as well.
Force generation and packaging has been the biggest hurdle to date, as
well as a fundamental understanding of [ionic polymer metal composite] (IPMC)
technology, as indicated by Moore. We have already begun to see dozens of
applications from touch screens to robots that utilize artificial muscle, and
it will be quite exciting to finally realize artificial limbs powered by IPMCs
or other technology as we further explore the interface of man and machine.
— Randall Alley, BSc, CP, FAAOP, CFT Chief
executive officer, biodesigns inc. and Practitioner Advisory Council member,
O&P Business News