Discovery will allow more sophisticated work at nanoscale
New method of fluid gating has implications for drug delivery, power generation and other uses

Date:
July 28, 2020
Source:
University of Houston
Summary:
The movement of fluids through small capillaries and channels
is crucial for processes ranging from blood flow through the
brain to power generation and electronic cooling systems, but
that movement often stops when the channel is smaller than 10
nanometers. Researchers have reported a new way to stimulate the
fluid flow by using a small increase in temperature or voltage.



FULL STORY ==========================================================================
The movement of fluids through small capillaries and channels is
crucial for processes ranging from blood flow through the brain to power generation and electronic cooling systems, but that movement often stops
when the channel is smaller than 10 nanometers.


========================================================================== Researchers led by a University of Houston engineer have reported a
new understanding of the process and why some fluids stagnate in these
tiny channels, as well as a new way to stimulate the fluid flow by
using a small increase in temperature or voltage to promote mass and
ion transport.

The work, published in ACS Applied Nano Materials, explores the movement
of fluids with lower surface tension, which allows the bonds between
molecules to break apart when forced into narrow channels, stopping the
process of fluid transport, known as capillary wicking. The research
was also featured on the journal's cover.

Hadi Ghasemi, Cullen Associate Professor of Mechanical Engineering at
UH and corresponding author for the paper, said this capillary force
drives liquid flow in small channels and is the critical mechanism for
mass transport in nature and technology -- that is, in situations ranging
from blood flow in the human brain to the movement of water and nutrients
from soil to plant roots and leaves, as well as in industrial processes.

But differences in the surface tension of some fluids causes the wicking process -- and therefore, the movement of the fluid -- to stop when those channels are smaller than 10 nanometers, he said. The researchers reported
that it is possible to prompt continued flow by manipulating the surface tension through small stimuli, such as raising the temperature or using
a small amount of voltage.

Ghasemi said raising the temperature even slightly can activate movement
by changing surface tension, which they dubbed "nanogates." Depending
on the liquid, raising the temperature between 2 degrees Centigrade and
3 degrees C is enough to mobilize the fluid.

"The surface tension can be changed through different variables," he
said. "The simplest one is temperature. If you change temperature of
the fluid, you can activate this fluid flow again." The process can be fine-tuned to move the fluid, or just specific ions within it, offering
promise for more sophisticated work at nanoscale.

"The surface tension nanogates promise platforms to govern nanoscale functionality of a wide spectrum of systems, and applications can be
foreseen in drug delivery, energy conversion, power generation, seawater desalination, and ionic separation," the researchers wrote.

In addition to Ghasemi and first author Masoumeh Nazari, researchers
involved with the project include Sina Nazifi, Zixu Huang, Tian Tong
and Jiming Bao, all with the University of Houston, and Kausik Das and
Habilou Ouro-Koura, both with the University of Maryland Eastern Shore.

Funding for the project came from the Air Force Office of Scientific
Research, the National Science Foundation and the U.S. Department of
Education.


========================================================================== Story Source: Materials provided by University_of_Houston. Original
written by Jeannie Kever.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Masoumeh Nazari, Sina Nazifi, Zixu Huang, Tian Tong, Habilou
Ouro-Koura,
Jiming Bao, Kausik Das, Hadi Ghasemi. Surface Tension Nanogates
for Controlled Ion Transport. ACS Applied Nano Materials, 2020;
3 (7): 6979 DOI: 10.1021/acsanm.0c01304 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200728130839.htm

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