April 2018^ DISCOVER^55Army is interested in preventing battlefield
friendly fire by developing threads with
special optical qualities that respond to
laser sights. Fink and his collaborators
have addressed this by weaving filaments
with different reflective qualities into a
kind of plaid pattern that’s instantly vis-
ible through a comrade’s laser sight. It’s a
clear signal not to shoot.
This project isn’t just a professional
prospect for Fink. Saving lives in combat is
a personal goal. When he was 2 years old,
his deeply religious family emigrated from
the United States to Israel. His parents
signed him up for theological training, but he dropped out
as a teenager to join the military. “This was 1984 to ’87,” he
says, a period when Israel was building settlements in occu-
pied territory and conflict was high. “It was very intense
with a lot of people getting injured and killed,” he says.
“You see how close you always are to making a mistake.”
Fink not only witnessed fratricide in his own unit, but a
similar incident took his cousin’s life.
His response, after completing three years of service, was
to flee. He lived out of a backpack, visiting places like the
Philippines, Nepal and the U.S. But his father had other
ideas and enrolled him in the Technion-Israel Institute of
Technology, signing him up for the chemical engineering
program. “It seemed to me very mundane,” Fink recalls.
So to keep himself entertained, he also took up physics.
The combination was fortuitous. “Chemical engineering
has to do with processing fluids,” he explains.
Today, he applies those principles to building
physical systems using optics and electronics.
Not that this was obvious when Fink
graduated and joined the Ph.D. program at
MIT in 1995. Enrolled in materials science,
he drifted in search of a research project,
interviewing with dozens of professors
across a broad spectrum of fields. One of
them was Ned Thomas, a materials scientist
who was involved in a secret multimillion-
dollar program for the Defense Advanced
Research Projects Agency (DARPA) to
create a mechanism that would reflect light
from any direction.
Thomas invited Fink to attend a meeting where MIT
scientists would discuss a plan for tackling this problem.
As Fink prepared, he started to look at dielectric materi-
als — insulators and semiconductors that are layered to
make high-precision mirrors — and a very simple question
came into his head. “I knew from my optics studies that
layered systems reflect, but the angle is limited,” he says.
What he couldn’t find was a theoretical basis for this rule
of thumb. So at the meeting, he naively asked if anybody
knew a formula to determine the angle at which multilay-
ered dielectrics stop reflecting. “I was sure one of them
was going to say, ‘There’s this optics course I’m giving next
term,’ ” Fink recalls. “But the room was silent.”
He immediately started to work on the problem, and sev-
eral weeks and analyses later, he found there is no physicalFink displays chunky preforms that will become fibers once they’re processed in the draw tower. Behind the preforms sits a prototype military helmet
covered in functional fabric. The fabric responds to a gun’s laser sight, signalling to a shooter whether or not the helmet-wearer is an enemy.ELECTRONIC
TEXTILES COULD
BE WORN AS
GARMENTS,
IMPLANTED
INTO A BODY
OR BLANKETED
ACROSS A CITY.