Darlene Brezinski, PhD, Technical Editor 03.01.16
With all the new technology that seems to be developing faster than we can report it, I thought I would continue with a quick overview of some interesting items on the horizon.
● Birds have often inspired research on color fading and, if you have noticed, colorful birds do not turn gray as they age. Researchers at the University of Sheffield, South Yorkshire, U.K., say it comes down to the way color is created in the feathers. Rather than depending on pigments and dyes, which naturally fade, the birds are able to control and change the nanostructures that create the vibrant colors of their feathers.
Using X-ray scattering at the ESRF facility in France to examine the blue and white feathers of the jay, researchers found that birds demonstrate a surprising level of control and sophistication in producing colors. Instead of simply using dyes and pigments that would fade over time, the birds use well-controlled changes to the nanostructure to create their vividly colored feathers - which are possibly used for jays to recognize one another. The jay is able to pattern these different colors along an individual feather barb - the equivalent of having many different colors along a single human hair.
The jay’s feather, which goes from ultra violet in color through to blue and into white, is made of a nanostructured spongy keratin material, exactly the same kind of material human hair and fingernails are made from. The researchers found that the jay is able to demonstrate amazing control over the size of the holes in this sponge-like structure and fix them at very particular sizes, determining the color that we see reflected from the feather. This is because when light hits the feather the size of these holes determines how the light is scattered and, therefore, the color that is reflected. As a result, larger holes mean a broader wavelength reflectance of light, which creates the color white. Conversely, a smaller, more compact structure, results in the color blue.
If the colors were formed using pigments created from the bird’s diet, the feather color would fade over time. However, since nature has developed a way to create the colors through structural changes, any nanostructure will remain intact, explaining why birds never go grey as they age. In contrast, humans rely on pigments to color hair and, as these are not produced to the same extent as we age, we consequently go grey.
Dr. Andrew Parnell, from the University of Sheffield’s Department of Physics and Astronomy said: “Conventional thought was that to control light using materials in this way we would need ultraprecise and controlled structures with many different processing stages, but if nature can assemble this material ‘on the wing’, then we should be able to do it synthetically too.” Dr. Parnell added: “This discovery means that in the future, we could create long-lasting colored coatings and materials synthetically. We have discovered it is the way in which it is formed and the control of this evolving nanostructure – by adjusting the size and density of the holes in the spongy like structure – that determines what color is reflected.
Researcher Dr Daragh McLoughlin of AkzoNobel Decorative Paints Material Science Research Team added: "We aim to encourage and stimulate the innovation of more sustainable products that have eco-premium benefits. This exciting new insight may help us to find new ways of making paints that stay brighter and fresher-looking for longer, while also having a lower carbon footprint." The research findings were being published in Nature Scientific Reports (December 2015). For more information see: http://www.sheffield.ac.uk/news/
● Scientists at Russia’s ITMO University, led by Aleksandr V. Yakovlev and Alexandr V. Vinogradov, have developed a colorless titanium dioxide-based colloidal ink that doesn't require high-temperature fixing, and that can be applied to a wide variety of surfaces. The researchers can control the color produced on surfaces by varying the thickness of ink deposition from a normal inkjet printer. Creating a vibrant red is still a challenge but certainly the technology is ‘green’ and is stable under UV exposure.
Previous research has investigated printing color by light interference, but these attempts have required high-temperature fixing or specialized printing surfaces. A paper on the research was recently published in the journal ACS Nano.
● And, how about this for leading edge technology: A novel 4D printing method. A team of scientists at the Wyss Institute for Biologically Inspired Engineering at Harvard University and the Harvard John A. Paulson School of Engineering and Applied Sciences has evolved their microscale 3D printing technology to the fourth dimension, time. Inspired by natural structures like plants, which respond and change their form over time according to environmental stimuli, the team has unveiled 4D-printed hydrogel composite structures that change shape upon immersion in water.
"We have now gone beyond integrating form and function to create transformable architectures," said Jennifer Lewis, Sc.D., senior author on the new study. In nature, flowers and plants have tissue compositions and microstructures that result in dynamic morphologies that change according to their environments. Mimicking the variety of shape changes undergone by plant organs such as tendrils, leaves, and flowers in response to environmental stimuli like humidity and/or temperature, the 4D-printed hydrogel composites developed by Lewis and her team are programmed to contain precise, localized swelling behaviors. Importantly, the hydrogel composites contain cellulose fibrils that are derived from wood and are similar to the microstructures that enable shape changes in plants.
The composite ink that the team uses flows like liquid through the printhead, yet rapidly solidifies once printed. A variety of hydrogel materials can be used interchangeably resulting in different stimuli-responsive behaviors, while the cellulose fibrils can be replaced with other anisotropic fillers of choice, including conductive fillers.
"What’s remarkable about this 4D printing advance made by Jennifer and her team is that it enables the design of almost any arbitrary, transformable shape from a wide range of available materials with different properties and potential applications, truly establishing a new platform for printing self-assembling, dynamic microscale structures that could be applied to a broad range of industrial and medical applications," said Wyss Institute Founding Director Donald Ingber, M.D., Ph.D. This work was supported by funding from the Army Research Office (ARO) and the National Science Foundation’s Materials Research Science and Engineering Center (MRSEC). More information on this technique may be obtained from their website: http://wyss.harvard.edu/
● From the University of Illinois we have a new polymer damage-indicating system. Damage developing in a material is usually difficult to see until something breaks or fails. A new polymer damage-indication-system automatically highlights areas that are cracked, scratched or stressed, allowing engineers to address problem areas before they become more problematic.
The early warning system could have numerous application areas. Led by U. of I. materials science and engineering professor Nancy Sottos and aerospace engineering professor Scott White, the researchers published their work in the journal Advanced Materials.
Polymers are susceptible to damage in the form of small cracks that are often difficult to detect. Even at small scales, crack damage can significantly compromise the integrity and functionality of polymer materials,” Sottos said. “We developed a very simple but elegant material to autonomously indicate mechanical damage.”
When cracks form, microbeads embedded in the material break open and cause a chemical reaction that highlights the damaged area. The researchers embedded tiny microcapsules of a pH-sensitive dye in an epoxy resin. If the polymer forms cracks or suffers a scratch, stress or fracture, the capsules break open. The dye reacts with the epoxy, causing a dramatic color change from light yellow to a bright red.
The deeper the scratch or crack, the more microcapsules are broken, and the more intense the color. Tiny microscopic cracks of only 10 micrometers are enough to cause a color change, indicating a loss of some structural integrity. "Detecting damage before significant corrosion or other problems can occur provides increased safety and reliability for coated structures and composites,” White said. White and Sottos are affiliated with the Beckman Institute for Advanced Science and Technology at the U. of I.
The researchers demonstrated that the damage indication system worked well for a variety of polymer materials that can be applied to coat different substrates including metals, polymers and glasses. They also found that the system has long-term stability – no microcapsule leaking to produce false positives, and no color fading.
“We envision this self-reporting ability can be seamlessly combined with other functions such as self-healing and corrosion protection to both report and repair damage,” Sottos said. “Work is in progress to combine the ability to detect new damage with self-healing functionality and a secondary indication that reveals that crack healing has occurred.” For more information see www.illinois.edu/
.
● Birds have often inspired research on color fading and, if you have noticed, colorful birds do not turn gray as they age. Researchers at the University of Sheffield, South Yorkshire, U.K., say it comes down to the way color is created in the feathers. Rather than depending on pigments and dyes, which naturally fade, the birds are able to control and change the nanostructures that create the vibrant colors of their feathers.
Using X-ray scattering at the ESRF facility in France to examine the blue and white feathers of the jay, researchers found that birds demonstrate a surprising level of control and sophistication in producing colors. Instead of simply using dyes and pigments that would fade over time, the birds use well-controlled changes to the nanostructure to create their vividly colored feathers - which are possibly used for jays to recognize one another. The jay is able to pattern these different colors along an individual feather barb - the equivalent of having many different colors along a single human hair.
The jay’s feather, which goes from ultra violet in color through to blue and into white, is made of a nanostructured spongy keratin material, exactly the same kind of material human hair and fingernails are made from. The researchers found that the jay is able to demonstrate amazing control over the size of the holes in this sponge-like structure and fix them at very particular sizes, determining the color that we see reflected from the feather. This is because when light hits the feather the size of these holes determines how the light is scattered and, therefore, the color that is reflected. As a result, larger holes mean a broader wavelength reflectance of light, which creates the color white. Conversely, a smaller, more compact structure, results in the color blue.
If the colors were formed using pigments created from the bird’s diet, the feather color would fade over time. However, since nature has developed a way to create the colors through structural changes, any nanostructure will remain intact, explaining why birds never go grey as they age. In contrast, humans rely on pigments to color hair and, as these are not produced to the same extent as we age, we consequently go grey.
Dr. Andrew Parnell, from the University of Sheffield’s Department of Physics and Astronomy said: “Conventional thought was that to control light using materials in this way we would need ultraprecise and controlled structures with many different processing stages, but if nature can assemble this material ‘on the wing’, then we should be able to do it synthetically too.” Dr. Parnell added: “This discovery means that in the future, we could create long-lasting colored coatings and materials synthetically. We have discovered it is the way in which it is formed and the control of this evolving nanostructure – by adjusting the size and density of the holes in the spongy like structure – that determines what color is reflected.
Researcher Dr Daragh McLoughlin of AkzoNobel Decorative Paints Material Science Research Team added: "We aim to encourage and stimulate the innovation of more sustainable products that have eco-premium benefits. This exciting new insight may help us to find new ways of making paints that stay brighter and fresher-looking for longer, while also having a lower carbon footprint." The research findings were being published in Nature Scientific Reports (December 2015). For more information see: http://www.sheffield.ac.uk/news/
● Scientists at Russia’s ITMO University, led by Aleksandr V. Yakovlev and Alexandr V. Vinogradov, have developed a colorless titanium dioxide-based colloidal ink that doesn't require high-temperature fixing, and that can be applied to a wide variety of surfaces. The researchers can control the color produced on surfaces by varying the thickness of ink deposition from a normal inkjet printer. Creating a vibrant red is still a challenge but certainly the technology is ‘green’ and is stable under UV exposure.
Previous research has investigated printing color by light interference, but these attempts have required high-temperature fixing or specialized printing surfaces. A paper on the research was recently published in the journal ACS Nano.
● And, how about this for leading edge technology: A novel 4D printing method. A team of scientists at the Wyss Institute for Biologically Inspired Engineering at Harvard University and the Harvard John A. Paulson School of Engineering and Applied Sciences has evolved their microscale 3D printing technology to the fourth dimension, time. Inspired by natural structures like plants, which respond and change their form over time according to environmental stimuli, the team has unveiled 4D-printed hydrogel composite structures that change shape upon immersion in water.
"We have now gone beyond integrating form and function to create transformable architectures," said Jennifer Lewis, Sc.D., senior author on the new study. In nature, flowers and plants have tissue compositions and microstructures that result in dynamic morphologies that change according to their environments. Mimicking the variety of shape changes undergone by plant organs such as tendrils, leaves, and flowers in response to environmental stimuli like humidity and/or temperature, the 4D-printed hydrogel composites developed by Lewis and her team are programmed to contain precise, localized swelling behaviors. Importantly, the hydrogel composites contain cellulose fibrils that are derived from wood and are similar to the microstructures that enable shape changes in plants.
The composite ink that the team uses flows like liquid through the printhead, yet rapidly solidifies once printed. A variety of hydrogel materials can be used interchangeably resulting in different stimuli-responsive behaviors, while the cellulose fibrils can be replaced with other anisotropic fillers of choice, including conductive fillers.
"What’s remarkable about this 4D printing advance made by Jennifer and her team is that it enables the design of almost any arbitrary, transformable shape from a wide range of available materials with different properties and potential applications, truly establishing a new platform for printing self-assembling, dynamic microscale structures that could be applied to a broad range of industrial and medical applications," said Wyss Institute Founding Director Donald Ingber, M.D., Ph.D. This work was supported by funding from the Army Research Office (ARO) and the National Science Foundation’s Materials Research Science and Engineering Center (MRSEC). More information on this technique may be obtained from their website: http://wyss.harvard.edu/
● From the University of Illinois we have a new polymer damage-indicating system. Damage developing in a material is usually difficult to see until something breaks or fails. A new polymer damage-indication-system automatically highlights areas that are cracked, scratched or stressed, allowing engineers to address problem areas before they become more problematic.
The early warning system could have numerous application areas. Led by U. of I. materials science and engineering professor Nancy Sottos and aerospace engineering professor Scott White, the researchers published their work in the journal Advanced Materials.
Polymers are susceptible to damage in the form of small cracks that are often difficult to detect. Even at small scales, crack damage can significantly compromise the integrity and functionality of polymer materials,” Sottos said. “We developed a very simple but elegant material to autonomously indicate mechanical damage.”
When cracks form, microbeads embedded in the material break open and cause a chemical reaction that highlights the damaged area. The researchers embedded tiny microcapsules of a pH-sensitive dye in an epoxy resin. If the polymer forms cracks or suffers a scratch, stress or fracture, the capsules break open. The dye reacts with the epoxy, causing a dramatic color change from light yellow to a bright red.
The deeper the scratch or crack, the more microcapsules are broken, and the more intense the color. Tiny microscopic cracks of only 10 micrometers are enough to cause a color change, indicating a loss of some structural integrity. "Detecting damage before significant corrosion or other problems can occur provides increased safety and reliability for coated structures and composites,” White said. White and Sottos are affiliated with the Beckman Institute for Advanced Science and Technology at the U. of I.
The researchers demonstrated that the damage indication system worked well for a variety of polymer materials that can be applied to coat different substrates including metals, polymers and glasses. They also found that the system has long-term stability – no microcapsule leaking to produce false positives, and no color fading.
“We envision this self-reporting ability can be seamlessly combined with other functions such as self-healing and corrosion protection to both report and repair damage,” Sottos said. “Work is in progress to combine the ability to detect new damage with self-healing functionality and a secondary indication that reveals that crack healing has occurred.” For more information see www.illinois.edu/
.