Holograms made of tiny particles of silver could double the amount of information that can be stored in digital optical devices, such as sensors, displays and medical imaging devices.
Researchers from the University of Cambridge have developed a new method for making multi-coloured holograms from a thin film of silver nanoparticles, which could greatly increase the storage capabilities of typical optical storage devices.
The interference produced by the interaction of light with the nanoparticles allows the holograms to go beyond the normal limits of diffraction, or the way in which waves spread or bend when they encounter an opening or obstacle. The results were recently published in the journal Proceedings of the National Academy of Sciences.
When metallic particles have dimensions on the nanoscale, they display iridescent colours. A noted example of this phenomenon is the Lycurgus cup, which was made in the 4th century during the Roman Empire, and changes colour when held up to the light. An optical phenomenon, known as dichroism, occurs when the colour of the cup changes from green to red according to the position of the light source.
Roman artisans made the cup by incorporating nanoparticles into glass, although they would have been unaware of the specific physical characteristics responsible for the colours observed in the cup. Only in the last 20 years have scientists begun to understand this phenomenon, but they have not been able to utilise its effects in currently-available technology.
To apply this phenomenon in modern optics, an interdisciplinary team of researchers have created nanoscale metallic nanoparticle arrays that mimic the colour effects of the Lycurgus cup, to form multi-colour holograms. This breakthrough could lead to the shrinkage of standard bulky optical devices.
“This technology will lead to a new range of applications in the area of photonics, as conventional optical components simply cannot achieve this kind of functionality,” said Yunuen Montelongo, a PhD student from the Department of Engineering, who led the research. “The potential of this technology will be realised when they are mass produced and integrated into the next generation of ultra-thin consumer electronics.”
Using a single thin layer of silver, Montelongo and his colleagues patterned colourful holograms containing 16 million nanoparticles per square millimetre. Each nanoparticle, approximately 1000 times smaller than the width of a human hair, scatters light into different colours depending on its particular size and shape. The scattered light from each of the nanoparticles interacts and combines with all of the others to produce an image.
The device can display different images when illuminated with a different colour light, a property not seen before in a device of this type. Furthermore, when multiple light sources are shone simultaneously, a multi-colour image is projected.
These holographic devices are between 10 and 100 times smaller than just one of the millions of pixels used to produce a colour image on a typical laptop screen, yet they project a complete multi-colour image to the eye. This is possible through plasmonics: the study of how light interacts with metals on the nanoscale, which allows the researchers to go beyond the capability of conventional optical technologies.
“This hologram may find a wide range of applications in the area of displays, optical data storage, and sensors,” said PhD student Calum Williams, a co-author of the paper. “However, scalable approaches are needed to fulfil the potential of this technology.”
Currently, the team is exploring various optical mechanisms involved in the light-matter interaction at nanoscale. The future research will involve the construction of three-dimensional dynamic displays for consumer electronics and the researchers are already looking into tuning these devices for reconfigurable display technologies.
– See more at: http://www.cam.ac.uk/research/news/nanotechnology-used-to-create-next-generation-holograms-for-information-storage#sthash.umQbQBsi.dpuf
By now I’m sure you’ve heard about the discovery of Einstein’s gravitational waves. When Einstein predicted that space-time could be seen as a fabric that bends around heavy gravitation it was a purely theoretical exercise. 100 years later, we’ve finally discovered a way to measure ripples in this ‘fabric’. The measurements were made at LIGO, the Laser Interferometer Gravitational-Wave Observatory by Caltech and MIT.
A seasoned veteran of explaining science to non-scientists, Greene clearly explains how this measurement was made and what it could mean for the future of the scientific study of gravity.
After 340 days on board the International Space Station, astronaut Scott Kelly and cosmonaut Mikhail Kornienko are scheduled to return home March 1. Tuesday’s departure will mark the end of a stint in orbit about twice as long as a typical visit to the space station.
Kelly and Kornienko left Earth on March 27, 2015, for an expedition designed to study the physical and psychological challenges that future astronauts will have to endure on trips to far-flung locales such as Mars. Back on Earth, Kelly’s identical twin brother, Mark, is serving as an experimental control so researchers can compare how space changes a person with the same genetic makeup.
A year is a long time, but it’s not the longest sojourn to low Earth orbit. That honor goes to cosmonaut Valeri Polyakov, who stayed on space station Mir for nearly 438 days in 1994 and 1995.
No word yet on whether the gorilla suit that Mark recently sent his brother is staying behind.
Researchers have found one of the oldest and most detailed fossils of the central nervous system yet identified, from a crustacean-like animal that lived more than 500 million years ago. The fossil, from southern China, has been so well preserved that individual nerves are visible, the first time this level of detail has been observed in a fossil of this age.
The findings, published in the Proceedings of the National Academy of Sciences, are helping researchers understand how the nervous system of arthropods – creepy crawlies with jointed legs – evolved. Finding any fossilised soft tissue is rare, but this particular find, by researchers in the UK, China and Germany, represents the most detailed example of a preserved nervous system yet discovered.
The animal, called Chengjiangocaris kunmingensis, lived during the Cambrian ‘explosion’, a period of rapid evolutionary development about half a billion years ago when most major animal groups first appear in the fossil record. C. kunmingensis belongs to a group of animals called fuxianhuiids, and was an early ancestor of modern arthropods – the diverse group that includes insects, spiders and crustaceans.
“This is a unique glimpse into what the ancestral nervous system looked like,” said study co-author Dr Javier Ortega-Hernández, of the University of Cambridge’s Department of Zoology. “It’s the most complete example of a central nervous system from the Cambrian period.”
Over the past five years, researchers have identified partially-fossilised nervous systems in several different species from the period, but these have mostly been fossilised brains. And in most of those specimens, the fossils only preserved details of the profile of the brain, meaning the amount of information available has been limited.
C. kunmingensis looked like a sort of crustacean, with a broad, almost heart-shaped head shield, and a long body with pairs of legs of varying sizes. Through careful preparation of the fossils, which involved chipping away the surrounding rock with a fine needle, the researchers were able to view not only the hard parts of the body, but fossilised soft tissue as well.
The vast majority of fossils we have are mostly bone and other hard body parts such as teeth or exoskeletons. Since the nervous system and soft tissues are essentially made of fatty-like substances, finding them preserved as fossils is extremely rare. The researchers behind this study first identified a fossilised central nervous system in 2013, but the new material has allowed them to investigate the significance of these finding in much greater depth.
The central nervous system coordinates all neural and motor functions. In vertebrates, it consists of the brain and spinal cord, but in arthropods it consists of a condensed brain and a chain-like series of interconnected masses of nervous tissue called ganglia that resemble a string of beads.
Like modern arthropods, C. kunmingensis had a nerve cord – which is analogous to a spinal cord in vertebrates – running throughout its body, with each one of the bead-like ganglia controlling a single pair of walking legs.
Closer examination of the exceptionally preserved ganglia revealed dozens of spindly fibres, each measuring about five thousandths of a millimetre in length. “These delicate fibres displayed a highly regular distribution pattern, and so we wanted to figure out if they were made of the same material as the ganglia that form the nerve cord,” said Ortega-Hernández. “Using fluorescence microscopy, we confirmed that the fibres were in fact individual nerves, fossilised as carbon films, offering an unprecedented level of detail. These fossils greatly improve our understanding of how the nervous system evolved.”
For Ortega-Hernández and his colleagues, a key question is what this discovery tells us about the evolution of early animals, since the nervous system contains so much information. Further analysis revealed that some aspects of the nervous system in C. kunmingensis appear to be structured similar to that of modern priapulids (penis worms) and onychophorans (velvet worms), with regularly-spaced nerves coming out from the ventral nerve cord.
In contrast, these dozens of nerves have been lost independently in the tardigrades (water bears) and modern arthropods, suggesting that simplification played an important role in the evolution of the nervous system.
Possibly one of the most striking implications of the study is that the exceptionally preserved nerve cord of C. kunmingensis represents a unique structure that is otherwise unknown in living organisms. The specimen demonstrates the unique contribution of the fossil record towards understanding the early evolution of animals during the Cambrian period. “The more of these fossils we find, the more we will be able to understand how the nervous system – and how early animals – evolved,” said Ortega-Hernández.
- Jie Yang et. al. The fuxianhuiid ventral nerve cord and early nervous system evolution in Panarthropoda. PNAS, 2016 DOI:10.1073/pnas.1522434113