by David Geer
Contact the author at geercom@alltel.net
Artificial Muscle (EPAMs)
Today, Robotic Applications to Follow
Electroactive Polymer Artificial Muscles (EPAMs) are a new actuating/motion technology
based on polymers that react to electricity. The new actuators are useful across applications
where motors are not as efficient or are simply not feasible.
The basic EPAM is a rubber sheet
made of a custom-formulated
elastomer, explains Ilya Polyakov,
a senior mechanical engineer at
Artificial Muscle, Inc., creators of the
EPAM. The polymer is applied so that
electrodes plate the rubber sheeting
on both top and bottom. As voltage
is applied positively and negatively
through these electrodes, the
dielectric rubber — which doesn’t
permit the flow of electricity —
produces an electrostatic force.
This force pulls the electrodes
together, pushing the EPAM out
side-to-side at tenss of pounds-per-square-inch. This actuation is then
harnessed for practical uses, including
robot muscles.
“Because our muscle membrane
squeezes out proportionally to the
This small piece of hardware uses EPAM
technology to auto focus optical lenses
in mobile/cell phone cameras,
according to Polyakov. A 9. 5 mm EPAM
actuator positions the lens based on
data from a CMOS sensor. The
hardware is encircled by a flex circuit
power supply at 1.3 kV. The unit is
specifieded to fit the standard SMIA
9. 5 mm phone camera form factor.
electrical field applied, we can simply
control the amount of movement,”
says Polyakov.
Harnessing EPAM
Proper ties
One of the most common
building blocks using the EPAM is
the universal muscle actuator (UMA)
configuration, which is a jumping-off
point for more complex applications.
This configuration attaches two EPAM
sheets/films at their centers, with a
lightweight spacer between them.
“Each stack of film is attached to
a frameso it can be mounted. Each
stack is also attached to an output
disk which transmits the force and
stroke of the expanding film to some
load in order to perform work,”
This larger solenoid coil at left is used
in commercial pneumatic valves.
The coil at right — a 9. 5 mm actuator
stack based on EPAM technology
— is capable of the same workload
at a fraction of the commercial
solenoid’s mass and volume. The
commercial part weighs 70 grams
compared to the EPAM’s 8.
explains Polyakov. One practical use
for EPAMs and UMAs is in valves.
Existing valve systems convert high
speed rotary motors running at
thousands of RPMs to low speed
linear motion for valve parts that
move a few feet per second.
The EPAM actuator eliminates the
mechanical steps necessary for the
speed conversion by offering low
speed linear motion in the initial
instance. This technology is called a
roll configuration actuator, which
employs a large stretch of artificial
muscle film/membrane wrapped
around a compressed spring.
The spring pushes the cylinder of
wound film into tension, Polyakov
explains. “Once in tension, the
application of the electric field to
the film causes it to relax and
produce a force imbalance between
the spring and the connected films,
The valve on the left is an OTS
proportional solenoid valve. The one
on the right is EPAM powered
with identical flow specs, and a directly
attached power supply board. It weighs
1/7th the original unit and operates
at 1/10th the power.
10 SERVO 12.2008
