Cicada-inspired waterproof surfaces closer to reality

Date:
October 22, 2020
Source:
University of Illinois at Urbana-Champaign, News Bureau
Summary:
A multidisciplinary group that studies the physical and chemical
properties of insect wings has demonstrated the ability to reproduce
the nanostructures that help cicada wings repel water and prevent
bacteria from establishing on the surface. The new technique - which
uses commercial nail polish - is economical and straightforward,
and the researchers said it will help fabricate future high-tech
waterproof materials.



FULL STORY ==========================================================================
A multidisciplinary group that studies the physical and chemical
properties of insect wings has demonstrated the ability to reproduce
the nanostructures that help cicada wings repel water and prevent
bacteria from establishing on the surface. The new technique -- which
uses commercial nail polish -- is economical and straightforward, and
the researchers said it will help fabricate future high-tech waterproof materials.


==========================================================================
The team used a simplified version of a fabrication process -- called nanoimprinting lithography -- to make a template of the complex
pillar-shaped nanostructures on the wings of Neotibicen pruinosus,
an annual cicada found in the central region of the United States. The templates are fully dissolvable and produce replicas that average 94.4%
of the pillar height and 106% of the original wing, or master structure's pillar diameter, the researchers said.

The results of the study are published in the journal Nano Letters.

"We chose to work with wings of this species of cicada because our
past work demonstrates how the complex nanostructures on their wings
provide an outstanding ability to repel water. That is a highly desirable property that will be useful in many materials engineering applications,
from aircraft wings to medical equipment," said Marianne Alleyne, an
entomology professor at the University of Illinois at Urbana-Champaign,
who co-led the study with Donald Cropek, of the U.S. Army Corps of
Engineers' Construction Engineering Research Laboratory, and Nenad
Miljkovic, a professor of mechanical science and engineering at Illinois.

Nanoimprinting lithography is not new but can be labor-intensive and
expensive, the researchers said. Some approaches use toxic materials
that can damage the original copied object, like a delicate cicada
wing. Others require high temperatures that are not compatible with
biological samples such as plants or insects.

"Our process allows us to do this in an open lab at room temperature
and atmospheric pressure," Cropek said. "We use nail polish and
rubbing alcohol, which does not inflict any damage to the delicate wing nanostructures." In the lab, the team applies a quick-drying nail polish directly to a cicada wing, which is then left to cure at room temperature.

"It was not easy to find the right formula of nail polish because we
want to avoid one that will warp or stretch the template during removal," Alleyne said.

Once completed, the template can be coated with a polymer or metal then dissolved away, leaving only the replica metal or polymer.

To show the versatility of the new method, the team experimented with
two very different replica materials: copper metal and a flexible
silicon-based organic polymer called PDMS.

"We showed that the technique is compatible with physical vapor deposition
and electrochemical deposition of metals, oxides or ceramics, as well
as chemical vapor deposition and spin coating of softer materials like polymers," Miljkovic said.

"Copper is particularly interesting to us because of its inherent
antimicrobial properties, and our past work indicates that some cicada
species display antimicrobial properties on their wings," Alleyne
said. "We don't know if it is the chemicals on the wing's surface or
the physical nanostructures, or a combination of both chemistry and
topography, that produce the bactericidal activity, but being able
to produce materials with different chemistries and structures will
help us answer that fundamental question. This new, relatively simple fabrication method will ultimately help us design multifunctional
engineered materials."

========================================================================== Story Source: Materials provided by University_of_Illinois_at_Urbana-Champaign,_News_Bureau.

Original written by Lois Yoksoulian. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Junho Oh, Jacob B. Hoffman, Sungmin Hong, Kyoo D. Jo, Jessica
Roma'n-
Kustas, Julian H. Reed, Catherine E. Dana, Donald M. Cropek,
Marianne Alleyne, Nenad Miljkovic. Dissolvable Template
Nanoimprint Lithography: A Facile and Versatile Nanoscale
Replication Technique. Nano Letters, 2020; 20 (10): 6989 DOI:
10.1021/acs.nanolett.0c01547 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201022112620.htm

--- up 8 weeks, 3 days, 6 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)