Nav: Home

Flexible material shows potential for use in fabrics to heat, cool

July 02, 2020

A film made of tiny carbon nanotubes (CNT) may be a key material in developing clothing that can heat or cool the wearer on demand. A new North Carolina State University study finds that the CNT film has a combination of thermal, electrical and physical properties that make it an appealing candidate for next-generation smart fabrics.

The researchers were also able to optimize the thermal and electrical properties of the material, allowing the material to retain its desirable properties even when exposed to air for many weeks. Moreover, these properties were achieved using processes that were relatively simple and did not need excessively high temperatures.

"Many researchers are trying to develop a material that is non-toxic and inexpensive, but at the same time is efficient at heating and cooling," said Tushar Ghosh, co-corresponding author of the study. "Carbon nanotubes, if used appropriately, are safe, and we are using a form that happens to be inexpensive, relatively speaking. So it's potentially a more affordable thermoelectric material that could be used next to the skin." Ghosh is the William A. Klopman Distinguished Professor of Textiles in NC State's Wilson College of Textiles.

"We want to integrate this material into the fabric itself," said Kony Chatterjee, first author of the study and a Ph.D. student at NC State. "Right now, the research into clothing that can regulate temperature focuses heavily on integrating rigid materials into fabrics, and commercial wearable thermoelectric devices on the market aren't flexible either."

To cool the wearer, Chatterjee said, CNTs have properties that would allow heat to be drawn away from the body when an external source of current is applied.

"Think of it like a film, with cooling properties on one side of it and heating on the other," Ghosh said.

The researchers measured the material's ability to conduct electricity, as well as its thermal conductivity, or how easily heat passes through the material.

One of the biggest findings was that the material has relatively low thermal conductivity - meaning heat would not travel back to the wearer easily after leaving the body in order to cool it. That also means that if the material were used to warm the wearer, the heat would travel with a current toward the body, and not pass back out to the atmosphere.

The researchers were able to accurately measure the material's thermal conductivity through a collaboration with the lab of Jun Liu, an assistant professor of mechanical and aerospace engineering at NC State. The researchers used a special experimental design to more accurately measure the material's thermal conductivity in the direction that the electric current is moving within the material.

"You have to measure each property in the same direction to give you a reasonable estimate of the material's capabilities," said Liu, co-corresponding author of the study. "This was not an easy task; it was very challenging, but we developed a method to measure this, especially for thin flexible films."

The research team also measured the ability of the material to generate electricity using a difference in temperature, or thermal gradient, between two environments. Researchers said that they could take advantage of this for heating, cooling, or to power small electronics.

Liu said that while these thermoelectric properties were important, it was also key that they found a material that was also flexible, stable in air, and relatively simple to make.

"The point of this paper isn't that we achieved the best thermoelectric performance," Liu said. "We achieved something that can be used as a flexible, electronic, soft material that's easy to fabricate. It's easy to prepare this material, and easy to achieve these properties."

Ultimately, their vision for the project is to design a smart fabric that can heat and cool the wearer, along with energy harvesting. They believe that a smart garment could help reduce energy consumption.

"Instead of heating or cooling a whole dwelling or space, you would heat or cool the personal space around the body," Ghosh said. "If we could get the thermostat down a degree or two, that could save a tremendous amount of energy."
-end-
The paper, "In-plane Thermoelectric Properties of Flexible and Room Temperature Processable Doped Carbon Nanotube Films," was published in the journal ACS Applied Energy Materials. The paper was co-authored by Ankit Negi and Kyunghoon Kim, who are Ph.D. students at NC State. The research was supported by the National Science Foundation, under grants 1943813 and 1622451, and by the NC State Chancellor's Innovation Fund.

Note to editors: the abstract follows.

"In-plane Thermoelectric Properties of Flexible and Room Temperature Doped Carbon Nanotube Films."

DOI: 10.1021/acsaem.0c00995

Authors: Kony Chatterjee, Ankit Negi, Kyunghoon Kim, Jun Liu and Tushar K. Ghosh, North Carolina State University.

Published: June 29, ACS Applied Energy Materials.

Abstract: Soft materials with high power factors (PFs) and low thermal conductivity (κ) are critically important for integration of thermoelectric (TE) modules into flexible form factors for energy harvesting or cooling applications. Here, air stable p- and n-type multiwalled carbon nanotube (MWCNT) films with high power factors (up to 521 μW/mK2) are reported, with the n type doping carried out in a facile two-step process. The maximum figure of merit (ZT) of the p type and n-type CNTs are obtained as 0.019 and 0.015 at 300 K, respectively with all three transport properties - Seebeck coefficient, electrical conductivity, and κ - measured in-plane, providing a more accurate ZT. Using time-domain thermoreflectance (TDTR) we report a fast and non-contact measurement of κ without complex microfabrication or material processing.

Moreover, there is no material mismatch between the p- and n-type legs of the TE module. Such materials have the potential for widespread applications in inexpensive and scalable wearable harvesting and localized heating/cooling.

North Carolina State University

Related Carbon Nanotubes Articles:

How plantains and carbon nanotubes can improve cars
Researchers from the University of Johannesburg have shown that plantain, a starchy type of banana, is a promising renewable source for an emerging type of lighter, rust-free composite materials for the automotive industry.
New production method for carbon nanotubes gets green light
A new method of producing carbon nanotubes -- tiny molecules with incredible physical properties used in touchscreen displays, 5G networks and flexible electronics -- has been given the green light by researchers, meaning work in this crucial field can continue.
Growing carbon nanotubes with the right twist
Researchers synthetize nanotubes with a specific structure expanding previous theories on carbon nanotube growth.
Research shows old newspapers can be used to grow carbon nanotubes
New research has found that old newspaper provide a cheap and green solution for the bulk production of single walled carbon nanotubes.
Clean carbon nanotubes with superb properties
Scientists at Aalto University, Finland, and Nagoya University, Japan, have found a new way to make ultra-clean carbon nanotube transistors with superior semiconducting properties.
Dietary fiber effectively purifies carbon nanotubes
A dietary fiber can help separate out semiconducting carbon nanotubes used for making transistors for flexible electronics.
Why modified carbon nanotubes can help the reproducibility problem
Scientists at Tokyo Institute of Technology (Tokyo Tech) conducted an in-depth study on how carbon nanotubes with oxygen-containing groups can be used to greatly enhance the performance of perovskite solar cells.
Tensile strength of carbon nanotubes depends on their chiral structures
Single-walled carbon nanotubes should theoretically be extremely strong, but it remains unclear why their experimental tensile strengths are lower and vary among nanotubes.
New study reveals carbon nanotubes measurement possible for the first time
Swansea University scientists report an entirely new approach to manipulation of carbon nanotubes that allows physical measurements to be made on carbon nanotubes that have previously only been possible by theoretical computation.
Neural networks will help manufacture carbon nanotubes
A team of scientists from Skoltech's Laboratory of Nanomaterials proposed a neural-network-based method for monitoring the growth of carbon nanotubes, preparing the ground for a new generation of sophisticated electronic devices.
More Carbon Nanotubes News and Carbon Nanotubes Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Warped Reality
False information on the internet makes it harder and harder to know what's true, and the consequences have been devastating. This hour, TED speakers explore ideas around technology and deception. Guests include law professor Danielle Citron, journalist Andrew Marantz, and computer scientist Joy Buolamwini.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

How to Win Friends and Influence Baboons
Baboon troops. We all know they're hierarchical. There's the big brutish alpha male who rules with a hairy iron fist, and then there's everybody else. Which is what Meg Crofoot thought too, before she used GPS collars to track the movements of a troop of baboons for a whole month. What she and her team learned from this data gave them a whole new understanding of baboon troop dynamics, and, moment to moment, who really has the power.  This episode was reported and produced by Annie McEwen. Support Radiolab by becoming a member today at Radiolab.org/donate.