3 D P R I N T I N G
KEEPING AN EYE
ON 3D PRINTING
A team of researchers at the
University of Minnesota have, for the
first time, fully 3D printed an array of
light receptors on a hemispherical
surface. This discovery marks a
significant step toward creating a
"bionic eye" that could someday
help blind people see or sighted
people see better.
The research is published today
in Advanced Materials, a peerreviewed
scientific journal covering
materials science. The author also
holds the patent for 3D-printed
semiconducting devices.
"Bionic eyes are usually thought
of as science fiction, but now
we are closer than ever using a
multimaterial 3D printer," said
Michael McAlpine, a co-author
of the study and University of
Minnesota Benjamin Mayhugh
Associate Professor of Mechanical
Engineering.
Researchers started with a
hemispherical glass dome to show
how they could overcome the
challenge of printing electronics
on a curved surface. Using their
custom-built 3D printer, they started
with a base ink of silver particles.
The dispensed ink stayed in place
and dried uniformly instead of
running down the curved surface.
The researchers then used
semiconducting polymer materials to
print photodiodes, which convert light
into electricity. The entire process
takes about an hour.
Mr McAlpine says the most surprising
part of the process was the 25%
efficiency in converting the light into
electricity they achieved with the fully
3D-printed semiconductors.
"We have a long way to go to routinely
print active electronics reliably, but
our 3D-printed semiconductors are
now starting to show that they could
potentially rival the efficiency of
semiconducting devices fabricated
in microfabrication facilities," Mr
McAlpine says. "Plus, we can easily
print a semiconducting device on a
curved surface, and they can't."
Mr McAlpine and his team are
known for integrating 3D printing,
electronics, and biology on a single
platform. They received international
attention a few years ago for printing
a "bionic ear." Since then, they have
3D printed life-like artificial organs
for surgical practice, electronic fabric
that could serve as "bionic skin,"
electronics directly on a moving hand,
and cells and scaffolds that could
help people living with spinal cord
injuries regain some function.
Mr McAlpine's drive to create a
bionic eye is a little more personal.
"My mother is blind in one eye, and
whenever I talk about my work, she
says, 'When are you going to print
me a bionic eye?'" he says.
He says the next steps are to
create a prototype with more light
receptors that are even more
efficient. They'd also like to find a
way to print on a soft hemispherical
material that can be implanted into
a real eye.
The research team includes
University of Minnesota mechanical
engineering graduate student
Ruitao Su, postdoctoral researchers
Sung Hyun Park, Shuang-Zhuang
Guo, Kaiyan Qiu, Daeha Joung,
Fanben Meng, and undergraduate
student Jaewoo Jeong.
Pic: University of Minnesota,
McAlpine Group