August 1, 2017 These structural colors were printed on the same sheet of paper coated with copolymers through the application of ammonium persulfate and ethanol. Hydrogen bromide was used to neutralize the solvents and create a blank paper on which to print again. Credit: Rice University <\/p>\n
A chemical process that allows color images to be printed on specially coated paper and then erased so that different images can be printed on the same paper has been developed by researchers at Rice, Yonsei and Korea universities. <\/p>\n
The researchers explain the technique in a paper that will be published in the Aug. 4 issue of the journal Advanced Materials, which will feature images printed with this process on the cover. <\/p>\n
The technique makes use of structural colors, which have different properties than the ink dyes used for standard printing. The standard dyes absorb all the colors of the spectrum except for the color that is visible to the eye, such as red or blue, and the colors fade over time. Structural colors are determined by the selective reflections of certain colors at certain angles. They're made from one-dimensional stacks of layered polymers, called block copolymers. <\/p>\n
\"Copolymers are soft, stretchable and deformable,\" said Ned Thomas, Rice's Ernest Dell Butcher Professor of Engineering and professor of materials science and nanoengineering, of chemical and biomolecular engineering and of chemistry. \"You can swell or shrink them and change their shape and dimensions, which will affect which color they reflect.\" <\/p>\n
Thomas said one of his former Ph.D. students at MIT, Cheolmin Park, who is now a professor at Yonsei University, wanted to collaborate on developing printable and rewritable copolymer structural colors. <\/p>\n
The researchers found that they could use a single, colorless, water-based ink based on ammonium persulfate (APS) to control how the copolymers cross-link in various locations, which impacts their subsequent thickness and hence the structural colors that are reflected. APS stops the swelling of the copolymers, and the thin layer reflects blue. Ethanol was used to thicken the copolymers, which reflected red. By applying varying amounts of ethanol and APS to paper that is coated with copolymers, the researchers were able to control the swelling and shrinking of the molecules and generate the colors and patterns needed to create a picture. Large amounts of APS stopped all swelling, which resulted in black images because there was no reflection. <\/p>\n
The researchers also discovered that applying hydrogen bromide to the paper removed or erased the APS, so the reflections were neutralized, which \"reset\" the system so that the paper could be used again. They printed and erased images more than 50 times on the paper, with resolution similar to that of a commercial office inkjet printer. <\/p>\n
Thomas said refinements will be needed before this technique is commercially viable. Because ethanol evaporates, the reflective patterns disappear, so the researchers are looking for a substance that is less volatile and will maintain the colors indefinitely. They also need to find an alternative to hydrogen bromide, which is toxic and not environmentally friendly. <\/p>\n
Thomas thinks the technique has the potential to be cost-effective because it will require only one inkthe APSand a modified inkjet printer that uses paper coated with copolymers, which should cost \"pennies per sheet,\" he said. \"This could be really useful when you want to reconfigure, recolor and reshape messages on signs or clothing.\" <\/p>\n
Explore further: Flexible and cost-effective fabrication of nature inspired structural colors <\/p>\n
More information: Han Sol Kang et al, Printable and Rewritable Full Block Copolymer Structural Color, Advanced Materials (2017). DOI: 10.1002\/adma.201700084<\/p>\n
Journal reference: Advanced Materials <\/p>\n
Provided by: Rice University <\/p>\n
Throughout nature, colors generally arise from two sources: pigment colors and structural colors. For application purposes, pigments or dyes that absorb light are considered to be the traditional method to color materials ... <\/p>\n
Inspired by the varying colors that gleam off of beetle shells, scientists have developed color-shifting nanoparticles that can change hue even after being embedded into a material. A report on the new, inexpensive technique, ... <\/p>\n
\"Fast fashion\" might be cheap, but its high environmental cost from dyes polluting the water near factories has been well documented. To help stem the tide of dyes from entering streams and rivers, scientists report in the ... <\/p>\n
(Phys.org)In an effort to curb the adverse environmental impacts of paper production, researchers in a new study have developed a light-printable paperpaper that can be printed with UV light, erased by heating to 120 ... <\/p>\n
(Phys.org)A team of researchers at the Technical University of Denmark has developed a way to print colors onto a surface without using ink and which will not fade. In their paper published in the open-access journal Sciences ... <\/p>\n
Inspired by origami, North Carolina State University researchers have found a way to remotely control the order in which a two-dimensional (2-D) sheet folds itself into a three-dimensional (3-D) structure. <\/p>\n
The hardest thing about concrete just might be the problem of how to make the ubiquitous building material in an environmentally friendly manner. Recent laboratory results at Princeton University indicate that the challenge ... <\/p>\n
One of the most potent toxins known acts by welding the two strands of the famous double helix together in a unique fashion which foils the standard repair mechanisms cells use to protect their DNA. <\/p>\n
A chemical process that allows color images to be printed on specially coated paper and then erased so that different images can be printed on the same paper has been developed by researchers at Rice, Yonsei and Korea universities. <\/p>\n
Unlike the rigid plastic models from chemistry class, real chains of molecules can bend and stretch, like beads on an elastic cord. Some polymers, like DNA, are especially stretchy, a characteristic that can complicate attempts ... <\/p>\n
By some estimates, bacterial strains resistant to antibioticsso-called superbugs - will cause more deaths than cancer by 2050. <\/p>\n
Jean-Sabin McEwen knocks out a web search for \"North Dakota,\" \"night sky\" and \"flaring,\" and quickly finds a picture from space showing a glowing cluster bigger than Minneapolis. It's from oil and gas fields burning off methane, ... <\/p>\n
Please sign in to add a comment. Registration is free, and takes less than a minute. Read more <\/p>\n
<\/p>\n
More here: <\/p>\n
Technique enables printable and rewritable color images - Phys.org - Phys.Org<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" August 1, 2017 These structural colors were printed on the same sheet of paper coated with copolymers through the application of ammonium persulfate and ethanol. Hydrogen bromide was used to neutralize the solvents and create a blank paper on which to print again Continue reading