Babak ZIAIE, et al.
[ See also : KIM /
Electroactive paper ]
'Ferropaper' is new technology
for small motors, robots
Researchers at Purdue University have created a magnetic
"ferropaper" that might be used to make low-cost "micromotors"
for surgical instruments, tiny tweezers to study cells and
The material is made by impregnating ordinary paper - even
newsprint - with a mixture of mineral oil and "magnetic
nanoparticles" of iron oxide. The nanoparticle-laden paper can
then be moved using a magnetic field.
"Paper is a porous matrix, so you can load a lot of this
material into it," said Babak Ziaie, a professor of electrical
and computer engineering and biomedical engineering.
The new technique represents a low-cost way to make small
stereo speakers, miniature robots or motors for a variety of
potential applications, including tweezers to manipulate cells
and flexible fingers for minimally invasive surgery.
"Because paper is very soft it won't damage cells or tissue,"
Ziaie said. "It is very inexpensive to make. You put a droplet
on a piece of paper, and that is your actuator, or motor."
Once saturated with this "ferrofluid" mixture, the paper is
coated with a biocompatible plastic film, which makes it water
resistant, prevents the fluid from evaporating and improves
mechanical properties such as strength, stiffness and
Findings will be detailed in a research paper being presented
during the 23rd IEEE International Conference on Micro Electro
Mechanical Systems on Jan. 24-28 in Hong Kong. The paper was
written by Ziaie, electrical engineering doctoral student
Pinghung Wei and physics doctoral student Zhenwen Ding.
Because the technique is inexpensive and doesn't require
specialized laboratory facilities, it could be used in
community colleges and high schools to teach about micro
robots and other engineering and scientific principles, Ziaie
The magnetic particles, which are commercially available, have
a diameter of about 10 nanometers, or billionths of a meter,
which is roughly 1/10,000th the width of a human hair. Ferro
is short for ferrous, or related to iron.
"You wouldn't have to use nanoparticles, but they are easier
and cheaper to manufacture than larger-size particles," Ziaie
said. "They are commercially available at very low cost."
The researchers used an instrument called a field-emission
scanning electron microscope to study how well the
nanoparticle mixture impregnates certain types of paper.
"All types of paper can be used, but newspaper and soft tissue
paper are especially suitable because they have good
porosity," Ziaie said.
The researchers fashioned the material into a small
cantilever, a structure resembling a diving board that can be
moved or caused to vibrate by applying a magnetic field.
"Cantilever actuators are very common, but usually they are
made from silicon, which is expensive and requires special
cleanroom facilities to manufacture," Ziaie said. "So using
the ferropaper could be a very inexpensive, simple
alternative. This is like 100 times cheaper than the silicon
devices now available."
The researchers also have experimented with other shapes and
structures resembling Origami to study more complicated
The research is based at the Birck Nanotechnology Center in
Purdue's Discovery Park.
Zhenwen Ding, Pinghung Wei,
and Babak Ziaie
In this paper, we report on an inexpensive method for
fabricating mm-scale magnetic actuators using ferrofluid
impregnated paper. Different types of papers were loaded with
light oil-based ferrofluid, cut to cantilever shape, coated
with parylene C, and tested with an external magnetic field.
Cleanroom and filter paper were able to generate large forces
(>40 mg equivalent force) whereas soft tissue paper
provided the largest deflection (40° tip angle). Coating
parylene on ferro-paper not only improves the mechanical
properties but also allows the ferro-paper actuator to work in