A computational approach to understanding how ions in polymer liquids interact could
unlock better methods of creating lithium polymer batteries and purifying water.
Issei Nakamura, assistant professor of physics at Michigan Technological University, has received a National Science Foundation
(NSF) Faculty Early Career Program (CAREER) Award for his research on computational methods to simulate how polymeric liquids interact
with electric charges.
Nakamura researches soft materials — with particular focus on ionic liquids (liquid salts) and polymers — which can
be human-made like the plastics around your house, or natural like silk and DNA.
Even though ion-containing polymer liquids are used in many applications, such as
rechargeable batteries, we still lack a full understanding of how they work. In collaboration
with Amalie Frischknecht and Mark J. Stevens at Sandia National Laboratories, Nakamura studies how charged molecules — ions — interact within a polymer liquid
environment.
Ionic liquids possess attributes such as electrochemical stability, high charge density,
tunable polarity and low volatility that enable their widespread application in supercapacitors,
fuel cells and electrochemical actuators.
“Even a small difference in molecular charge difference has a huge effect on the macroscopic
thermodynamic properties of liquids,” Nakamura said.
Nakamura’s time-dependent simulations will help him and fellow researchers better
understand how molecules respond to an external electrostatic field and how those
reactions affect how polymers provide an insulating dielectric response.
“This simulation does calculations about how ions and molecules move as time proceeds,”
Nakamura said. “We see a charge distribution in the molecules. We visualize how ions
and molecules themselves interact with each other, but also extract information about
how the charges interact.”
Grants and Funding
National Science Foundation 1944211
And because polymers are frequently in motion, Nakamura’s simulations demonstrate
charge interactions among moving polymers and liquids. Polymers tend to be long and
unwieldy. Imagine running a hand through a cobweb and then trying to untangle it.
In a liquid, polymers can get sticky like the cobweb, or push away from ions and other
sections of its own polymer chains. These interactions are complex, and Nakamura uses
a finely tuned physics model to try to understand the motion better. If we can untangle
the cobweb, it opens up possibilities for new materials, better batteries, faster
water treatment and more.
Nanomaterial Simulations and Education
A significant component of any CAREER Award is the creation of educational materials
for the next generation of scientists. Nakamura has proposed to work with Keweenaw
K-12 schools to help students do computer simulations using open-source software.
Building on the programming knowledge many students already have — coding is learned
at increasingly younger ages, often through computer games or programmable toys —
Nakamura plans to demonstrate how students can visualize molecular motions using programming
or simulation software.
“That was impossible when I was a high school student,” he said. “We didn’t have that
kind of software and programming wasn’t common practice by high school students.”
Nakamura’s own interest in computer simulations comes from playing games that were
precursors to Nintendo as a child in Japan. His parents were strict about his schooling
and homework taking priority after school, so Nakamura began waking up early to get
in an hour or two of video games in the morning.
“That might have been the spark for my interest in the world of simulations,” he said,
joking that restricting screen time “might limit your child’s ability to become a
physicist.”
In all seriousness, Nakamura sees the world of computer simulations as another tool
by which to understand the world.
“Visualizing what we research is quite important, especially for students,” he said.
“Like some video games, simulations are just another way to learn.”
Michigan Technological University is a public research university, home to more than
7,000 students from 54 countries. Founded in 1885, the University offers more than
120 undergraduate and graduate degree programs in science and technology, engineering,
forestry, business and economics, health professions, humanities, mathematics, and
social sciences. Our campus in Michigan’s Upper Peninsula overlooks the Keweenaw Waterway
and is just a few miles from Lake Superior.