Squid, jellyfish and wrinkled skin inspire materials for anti-glare screens and encryption

August 21, 2016

PHILADELPHIA, Aug. 21, 2016 -- What do squid and jellyfish skin have in common with human skin? All three have inspired a team of chemists to create materials that change color or texture in response to variations in their surroundings. These materials could be used for encrypting secret messages, creating anti-glare surfaces, or detecting moisture or damage, they say.

The researchers will present their work today at the 252nd National Meeting & Exposition of the American Chemical Society (ACS). ACS, the world's largest scientific society, is holding the meeting here through Thursday. It features more than 9,000 presentations on a wide range of science topics.

"Our experimental materials use cracks, folds or wrinkles to mimic the surface engineering of skin," says Luyi Sun, Ph.D., who heads the research. "These new materials are unique because they change color or transparency when they're stretched or exposed to moisture."

Human fingers wrinkle when they've been submerged in water for a while. But jellyfish skin can also wrinkle, Sun's graduate student Songshan Zeng says. "When they're scared, some types of jellyfish form a wrinkled surface that is opaque and warns off predators," says Zeng, who has a leading role in the project. "That same surface is transparent when it's flat." Even more impressive is the reaction of a squid when it is startled: Muscles in its skin contract, exposing colored pigments that serve as camouflage.

Sun's team and their collaborator, Dianyun Zhang, Ph.D., who are all at the University of Connecticut, studied these three types of skin to determine how surface engineering alters their properties in response to changes in the environment. The researchers replicated the wrinkled surfaces by placing a rigid thin film of polyvinyl alcohol on a rubbery base of polydimethylsiloxane (PDMS). "Like finger skin, whenever part of the film is exposed to moisture, it swells slightly, generating wrinkles," Sun says. Because the wrinkled part of the film is opaque, it can be used to form patterns -- such as letters -- that appear when the film is moistened. Sun notes that his is one of very few teams studying the dynamics of moisture-induced wrinkles, including how long they last and how to reverse them.

The presence and degree of crosslinking between polymer chains in the thin film dictates whether the wrinkling is reversible. On the one hand, if the film is formulated without crosslinking, wrinkles can be generated by moisture and subsequently smoothed out, but they cannot form again. This would be useful for displaying a message and then permanently erasing it once it's read -- a feature that James Bond would appreciate, Zeng notes. On the other hand, if the film has a certain type of crosslinking, wrinkles generated by moisture can never be erased. Thus, a small label incorporating the technology could go inside a cell phone (or on any circuit board). If the phone fell into a toilet, permanent wrinkles would form on the label in any desired shape (such as the chemical formula for water, "H2O"). This would be a dead give-away to a vendor that a customer had voided the warranty.

The researchers are also working on another cell phone application for wrinkled materials. Because wrinkles scatter light rays in multiple directions, rather than reflecting them directly back at a viewer, a different formulation of the material could make a cheap and effective anti-glare screen for phones, the researchers note.

In a separate project, Sun's group mimicked squid skin by creating a PDMS base layer containing a small amount of fluorescent dye and coating it with a rigid thin film of polyvinyl alcohol/clay composite. The clay makes the surface layer prone to developing a multitude of tiny cracks and folds. Stretching the material opens the folds and cracks on the originally smooth surface, altering its topography and appearance. Depending on the formulation, the film can reversibly change color, luminesce or go from clear to opaque. One potential application is a smart window containing a clear material that could be stretched slightly so it turns opaque to provide privacy. The team is the first to make these types of materials, Sun says.

A press conference on this topic will be held Monday, Aug. 22, at 1 p.m. Eastern time in the Pennsylvania Convention Center. Reporters may check in at Room 307 in person, or watch live on YouTube http://bit.ly/ACSlivephiladelphia. To ask questions online, sign in with a Google account.
Sun acknowledges funding from the University of Connecticut and General Electric.

The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With nearly 157,000 members, ACS is the world's largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.

To automatically receive news releases from the American Chemical Society, contact newsroom@acs.org.

Note to journalists: Please report that this research is being presented at a meeting of the American Chemical Society.

Follow us: Twitter | Facebook


Bio-inspired design of highly sensitive and reversible mechanochromisms via surface engineering


In nature, some marine organisms, such as Vogtia and Cephalopods, have evolved to possess camouflage traits by dynamically and reversibly altering their transparency, fluorescence, and coloration via muscle controlled surface structures and morphologies. To mimic this display tactics, we designed similar deformation controlled surface engineering via strain-dependent cracks and folds to realize four types of novel mechanochromic devices: (1) transparency change mechanochromism (TCM), (2) luminescent mechanochromism (LM), (3) color alteration mechanochromism (CAM), and (4) encryption mechanochromism (EM), based on a simple bilayer system containing a rigid thin film and a soft substrate. These devices exhibit a wide scope of mechanochromic response with excellent sensitivity and reversibility. The TCM device can reversibly and instantly switch between transparent and opaque state upon stretching and releasing. The LM can emit intensive fluorescence as stretched with an ultrahigh strain sensitivity in comparison to strain sensors based on electrical resistance change. The CAM can turn fluorescent color from green to yellow to orange as stretched within 20% strain. The EM device can reversibly reveal and conceal any desirable patterns. These novel devices are promising for applications in smart windows, dynamic optical switches, strain sensors, encryption, etc.


Tuning dynamics of moisture responsive wrinkling surfaces


Surface instability such as wrinkles commonly occurs in various materials with a wide scope of dimensions. Herein, we introduce three types of moisture responsive wrinkling surfaces with different dynamics as exposed to high humid environment based on a bilayer structure. All the three surfaces are initially flat and forming wrinkles as moisturized but with different responsive behaviors upon being further moisturized, dried and re-moisturized. In the first responsive dynamics, the highly opaque wrinkling surface can be rapidly generated as being moisturized and sustains for ca. 30 s followed by rewinding to transparent flattening surface upon further moisture exposure. No wrinkling surface is created again upon being re-exposed to moisture. This allows the design of an intriguing moisture responsive encryption device with the capability of "erase after read". In the second dynamics, the wrinkling surface can be rapidly generated as being moisturized and keeps stable regardless of moisture exposure time. Upon drying, the winkles can release back to the original flattening surface. The wrinkling and flattening surface can be repeatedly and reversibly created upon multiple dry/moisture cycles. A corresponding novel application of breathing activated anti-counterfeit tab is demonstrated. In the third dynamics system, the wrinkling surface can be generated as being moisturized and keeps stable in moisturized and dried state. This surface can be applied as a water indicator for electronic circuit, anti-glare surface, and optical diffusor.

American Chemical Society

Related Cell Phone Articles from Brightsurf:

Cell phone location used to estimate COVID-19 growth rates
Cell phone location data shows that in counties where activity declined at workplaces and increased at home, coronavirus infection rates were lower.

Study: Anonymized cell phone location data can help monitor COVID-19 growth rates
In a new study published in JAMA Internal Medicine, researchers from Mount Auburn Hospital and the University of Pennsylvania analyzed anonymous, county-level cell phone location data and incidence of COVID-19.

To make a good impression, leave cell phone alone during work meetings
New hires especially should keep their cell phones stashed away during business meetings, a new study strongly implies.

Flat-panel technology could transform antennas, wireless and cell phone communications
Researchers at Los Alamos National Laboratory are reinventing the mirror, at least for microwaves, potentially replacing the familiar 3-D dishes and microwave horns we see on rooftops and cell towers with flat panels that are compact, versatile, and better adapted for modern communication technologies.

Cell phone injuries
Cell phones are mainstays of daily life. This observational study analyzed 20 years of data on people who went to emergency departments with head and neck injuries from cell phone use to estimate the number of injuries, learn what types of injuries there were, and understand how the injuries occurred, such as from distracted driving or walking.

Cell phone-based microscope leads to possible strategy for treating river blindness
River blindness, or onchocerciasis, is a disease caused by a parasitic worm (Onchocerca volvulus) found primarily in Africa.

Cell phone data coupled with sewage testing show drug use patterns
The drugs people inhale, inject or ingest ultimately end up in some form down the toilet.

Cell phone use and distracted driving begins in the mind
Even simple cell phone conversations can cause distracted driving. Researchers have found listening on the phone while driving creates a lag in the mind to extract itself from one object before fixing attention on another object.

What motivates parents to protect children from cell phone addiction?
A new study examined the role parental mediation can play in protecting children from the potential negative effects of smartphone use, comparing the perceived risk and different types of mediation and parenting styles.

Catching the IMSI-catchers: SeaGlass brings transparency to cell phone surveillance
University of Washington security researchers have developed a new system called SeaGlass to detect anomalies in the cellular landscape that can indicate where and when IMSI-catchers, cell-site simulators and other devices used in cell phone surveillance are present.

Read More: Cell Phone News and Cell Phone Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.