Researchers at Missouri University of Science and Technology are creating a new approach to reconstruct 3-D full-color holographic images by using just one layer of nanoscale metallic film. This work has a huge potential to change our daily lives by equipping our cell phones with 3-D floating displays and printing 3-D security marking onto credit cards.
Dr. Xiaodong Yang, an assistant professor in mechanical and aerospace engineering at Missouri S&T, and Dr. Jie Gao, an assistant professor of mechanical and aerospace engineering at Missouri S&T, describe their ultrathin full-color holograms in “ACS Nano.” And they illustrate their approach by reproducing several full-color holographic images with nanometer-scale aluminum thin films. A nanometer is one billionth of a meter, and some nanomaterials are only a few atoms in size.
The method described in the “ACS Nano” article “Full-Color Plasmonic Metasurface Holograms” involves the use of ultrathin nanometer-scale metallic films with metasurfaces that can manipulate the wavefront of light. The researchers’ metasurface hologram is one 35-nanometer thick aluminum film punctured with tiny rectangular holes of 160 nanometers by 80 nanometers with different orientation angles created by a microfabrication process known as focused ion beam milling.
Experimenting with the interplay of red, green and blue laser light on metasurface structures, the researchers demonstrated “clean and vivid full-color holographic images with high resolution and low noise.” The three primary colors — red, green and blue — were produced, and the secondary colors of cyan, magenta, yellow and white also were produced. To illustrate their reconstructed holographic images, they made “CMYW” letters, an apple and a Rubik’ cube. They believe the metasurface hologram holds promise for future applications, such as credit card security marking, biomedical imaging, 3-D floating displays and big-data storage.
“By adjusting the orientation angle of the nanoscale slits, we are able to fully tune the phase delay through the slit for realizing the phase modulation within the entire visible color range,” says Yang. “In addition, the amplitude modulation is achieved by simply including or not including the slit. Our holograms contain both amplitude and phase modulations at nanometer scale so that high resolution and low noise holographic images can be reconstructed.”
The researchers created the metasurface hologram by drilling out tiny rectangular slits with various orientation angles through the aluminum thin layer. Under a scanning electron microscope, the hologram looks like a needlepoint pattern.
“Different from the currently existing metasurface holograms which are mostly designed for limited colors, our wavelength-multiplexed method — by encoding additional phase shifts into the holograms and introducing tilted incident angle illumination of laser light — results in the successful reconstruction of almost all visible colors,” says Gao, co-author of the paper.
It’s like a Fitbit on steroids.
Researchers at Missouri University of Science and Technology have developed a multi-modal sensing device that can track the fine-grained activities and behavior of people with dementia — and it could help in Army combat training, too.
Dr. Debraj De, a postdoctoral fellow at Missouri S&T, and Dr. Sajal K. Das, the Daniel St. Clair Endowed Chair and department chair of computer science at Missouri S&T, created a wearable device for the wrist that can track a person’s movements, ambient environment, bio-signals and much more. In collaboration with Dr. Mignon Makos, a neurologist at Phelps County Regional Medical Center (PCRMC), the device is going to be tested for patient rehabilitation and routine evaluation.
“The smart chair and the wearable device are new, noninvasive strategies for earlier diagnosis and represent a partnership among scientists and physicians,” Makos says.
And, Das says, it might someday gain approval as a tracker during combat training at Fort Leonard Wood, Missouri.
Looking like an oversized watch, the sensing device has four basic functions. Like a fitness tracker, it records fine-grained movement. It also measures the wearer’s direct physical environment for temperature, humidity and barometric air pressure. It also will track health status through heart rate, respiration rate and galvanic skin response (a person’s skin reacts to stimuli through the sympathetic nervous system, producing a weak electrical current that indicates the wearer’s emotional state, such as being startled or agitated, De says). Finally, the sensing device has a functions like GPS and communication with Bluetooth beacons in proximity for various location contexts.
Learn more: Wearable tracker could help patients, soldiers
Missouri University of Science and Technology (commonly Missouri S&T and formerly known as the University of Missouri–Rolla and originally Missouri School of Mines and Metallurgy) is an institution of higher learning located in Rolla, Missouri, United States, and part of the University of Missouri System.
Most of its 8,642 students (Fall 2014 enrollment) study engineering, computing, mathematics and the sciences. Although known primarily as an engineering school, Missouri S&T has numerous majors in humanities, social sciences, arts, sciences and business.
The school is known for its repeated success in national engineering design competitions and its century-long tradition of aggrandized celebrations surrounding Saint Patrick’s Day.
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