Posts Tagged ‘ink’

An array of semitransparent organic pixels on top of a ultrathin sheet of gold. The thickness of both the organic islands and the underlying gold is more than one-hundred times thinner than a single neuron.

SUMMARY: A simple retinal prosthesis is under development. Fabricated using cheap and widely-available organic pigments used in printing inks and cosmetics, it consists of tiny pixels like a digital camera sensor on a nanometric scale. Researchers hope that it can restore sight to blind people.

Researchers led by Eric Glowacki, principal investigator of the organic nanocrystals subgroup in the Laboratory of Organic Electronics, Linköping University, have developed a tiny, simple photoactive film that converts light impulses into electrical signals. These signals in turn stimulate neurons (nerve cells). The research group has chosen to focus on a particularly pressing application, artificial retinas that may in the future restore sight to blind people. The Swedish team, specializing in nanomaterials and electronic devices, worked together with researchers in Israel, Italy and Austria to optimise the technology. Experiments in vision restoration were carried out by the group of Yael Hanein at Tel Aviv University in Israel. Yael Hanein’s group is a world-leader in the interface between electronics and the nervous system.

The results have recently been published in the scientific journal Advanced Materials.

The retina consists of several thin layers of cells. Light-sensitive neurons in the back of the eye convert incident light to electric signals, while other cells process the nerve impulses and transmit them onwards along the optic nerve to an area of the brain known as the “visual cortex.” An artificial retina may be surgically implanted into the eye if a person’s sight has been lost as a consequence of the light-sensitive cells becoming degraded, thus failing to convert light into electric pulses.

The artificial retina consists of a thin circular film of photoactive material, and is similar to an individual pixel in a digital camera sensor. Each pixel is truly microscopic — it is about 100 times thinner than a single cell and has a diameter smaller than the diameter of a human hair. It consists of a pigment of semi-conducting nanocrystals. Such pigments are cheap and non-toxic, and are commonly used in commercial cosmetics and tattooing ink.

“We have optimised the photoactive film for near-infrared light, since biological tissues, such as bone, blood and skin, are most transparent at these wavelengths. This raises the possibility of other applications in humans in the future,” says Eric Glowacki.

He describes the artificial retina as a microscopic doughnut, with the crystal-containing pigment in the middle and a tiny metal ring around it. It acts without any external connectors, and the nerve cells are activated without a delay.

“The response time must be short if we are to gain control of the stimulation of nerve cells,” says David Rand, postdoctoral researcher at Tel Aviv University. “Here, the nerve cells are activated directly. We have shown that our device can be used to stimulate not only neurons in the brain but also neurons in non-functioning retinas.”


No ink required to print on this paper — yet look how readable the type is. (Photo: University of California, Riverside/YouTube)


As much as 40 percent of our landfills consist of paper and cardboard, and a major source of that material comes from office supplies. Just think of all the paper that gets used and discarded on a daily basis through the printer in your office alone. Even if that paper gets recycled, it still presents a different sort of problem due to pollution associated with the ink removal process.

Then there’s the concern about deforestation. In the United States, about one-third of all harvested trees are used for paper and cardboard production.

Paper and printing is a problem, to be sure. But now, thanks to a breakthrough from a team of scientists at Shandong University in China, the University of California, Riverside, and Lawrence Berkeley National Laboratory, it might be a problem with a solution.

The researchers have invented a new type of rewritable paper that can be printed with light — no ink required. The paper feels like normal paper to the touch, but it’s coated in color-changing nanoparticles that react to UV light. The technology works simply enough: a UV light printer zaps the paper everywhere except where the text is meant to be. The text then boldly stands out against the clear, light-zapped background.

“The greatest significance of our work is the development of a new class of solid-state photoreversible color-switching system to produce an ink-free light-printable rewritable paper that has the same feel and appearance as conventional paper, but can be printed and erased repeatedly without the need for additional ink,” explained Yadong Yin, chemistry professor at the University of California, Riverside. “Our work is believed to have enormous economic and environmental merits to modern society.”

The researchers published a paper on their work in the journal Nano Letters.

The nanoparticles return to their original background state if left untreated for five days, so the text will disappear naturally. (It certainly beats a paper shredder.) But if you wanted to erase and rewrite onto the same paper sooner than that, it will also revert back if heated for only about 10 minutes at 250 degrees Fahrenheit. It’s kind of like a hardcopy version of Snapchat, assuming you’ve got the proper equipment on hand to erase a message after it’s been read.

“We believe the rewritable paper has many practical applications involving temporary information recording and reading, such as newspapers, magazines, posters, notepads, writing easels, product life indicators, oxygen sensors, and rewritable labels for various applications,” said Yin.

Aside from producing little waste, the technology is also inexpensive. The coating materials are so cheap that they add almost nothing to the cost of a sheet of paper. Meanwhile, the printing technology ought to be cheaper than traditional inkjet printers simply because no ink is required. (Imagine never having to change out your ink cartridge again!)

And of course, because the paper can be re-used more than 80 times before the effect is dulled, the technology saves on the cost of paper as well.

“Our immediate next step is to construct a laser printer to work with this rewritable paper to enable fast printing,” said Yin. “We will also look into effective methods for realizing full-color printing.”