Researchers from Cornell University’s School of Applied and Engineering Physics and Samsung’s Advanced Institute of Technology have created a first-of-its-kind metalens—a metamaterial lens—that can be focused using voltage instead of mechanically moving its components.
The proof of concept opens the door to a range of compact varifocal lenses for possible use in many imaging applications such as satellites, telescopes and microscopes, which traditionally focus light using curved lenses that adjust using mechanical parts. In some applications, moving traditional glass or plastic lenses to vary the focal distance is simply not practical due to space, weight or size considerations.
Metalenses are flat arrays of nano-antennas or resonators, less than a micron thick, that act as focusing devices. But until now, once a metalens was fabricated, its focal length was hard to change, according to Melissa Bosch, doctoral student and first author of a paper detailing the research in the American Chemical Society’s journal Nano Letters.
The innovation, developed in the collaboration between Samsung and Cornell researchers, involved merging a metalens with the well-established technology of liquid crystals to tailor the local phase response of the metalens. This allowed the researchers to vary the focus of the metalens in a controlled way by varying the voltage applied across the device.
“This combination worked out as we hoped and predicted it would,” said Bosch, who works in the lab of Gennady Shvets, professor of applied and engineering physics and senior author of the paper. “It resulted in an ultrathin, electrically tunable lens capable of continuous zoom and up to 20% total focal length shift.”
Samsung researchers are hoping to develop the technology for use in augmented reality glasses, according to Bosch. She sees many other possible applications such as replacing the optical lenses on satellites, spacecraft, drones, night-vision goggles, endoscopes and other applications where saving space and weight are priorities.
Maxim Shcherbakov, postdoctoral associate in the Shvets lab and corresponding author of the paper, said that researchers have made progress in marrying liquid crystals to nanostructures for the past decade, but nobody had applied this idea to lenses. Now the group plans to continue the project and improve the prototype’s capabilities.
“For instance,” Shcherbakov said, “this lens works at a single wavelength, red, but it will be much more useful when it can work across the color spectrum—red, green, blue.”
The Cornell research group is now developing a multiwavelength varifocal version of the metalens using the existing platform as a starting point.
“The optimization procedure for other wavelengths is very similar to that of red. In some ways, the hardest step is already finished, so now it is simply a matter of building on the work already done,” Bosch said.
Melissa Bosch et al, Electrically Actuated Varifocal Lens Based on Liquid-Crystal-Embedded Dielectric Metasurfaces, Nano Letters (2021). DOI: 10.1021/acs.nanolett.1c00356
Novel liquid crystal metalens offers electric zoom (2021, June 10)
retrieved 10 June 2021
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Researchers from the Disruptive & Sustainable Technologies for Agricultural Precision (DiSTAP) Interdisciplinary Research Group (IRG) of Singapore-MIT Alliance for Research and Technology (SMART), MIT’s research enterprise in Singapore, and Temasek Life Sciences Laboratory (TLL), highlight the potential of rapid and non-destructive analytical tools that provide tissue-cell or organelle-specific information on living plants in real time and can be used on any plant species.
In a perspective paper titled “Species-independent analytical tools for next-generation agriculture,” published in the scientific journal Nature Plants, SMART DiSTAP researchers report that they used two engineered plant nanosensors and portable Raman spectroscopy to detect biotic and abiotic stress, monitor plant hormonal signaling and characterize soil, phytobiome and crop health in a non-invasive or minimally invasive manner. The researchers discuss how the tools bridge the gap between model plants in the laboratory and field application for agriculturally relevant plants. They also provide an assessment of the future outlook, economic potential and implementation strategies for the integration of these technologies in future farming practices.
According to U.N. estimates, the global population is expected to grow by 2 billion within the next 30 years, giving rise to an expected increase in demand for food and agricultural products to feed the growing population. Today, biotic and abiotic environmental stresses such as plant pathogens, sudden fluctuations in temperature, drought, soil salinity, and toxic metal pollution—made worse by climate change—impair crop productivity and lead to significant losses in agriculture yield worldwide.
An estimated 11 to 30% yield loss of five major crops of global importance (wheat, rice maize, potato, and soybean) are caused by crop pathogens and insects; with the highest crop losses observed in regions already suffering from food insecurity. Against this backdrop, research into innovative technologies and tools are required for sustainable agricultural practices and meet the rising demand for food and food security—an issue that has drawn the attention of governments worldwide due to the COVID-19 pandemic.
The Plant nanosensors were developed at SMART DiSTAP. They are smaller than the width of a hair and can be inserted into the tissues and cells of plants to understand complex signaling pathways. The portable Raman spectroscopy, also developed at SMART DiSTAP, is a portable laser-based device that measures molecular vibrations induced by laser excitation, producing highly specific Raman spectral signatures that provide a fingerprint of a plant’s health. These tools are able to monitor stress signals in short time scales, ranging from seconds to minutes, allowing for early detection of stress signals in real-time.
“The use of plant nanosensors and Raman spectroscopy has the potential to advance our understanding of crop health, behavior, and dynamics in agricultural settings,” said Dr. Tedrick Thomas Salim Lew, the paper’s first author and a recent graduate student of the Massachusetts Institute of Technology (MIT). “Plants are highly complex machines within a dynamic ecosystem, and a fundamental study of its internal workings and diverse microbial communities of its ecosystem is important to uncover meaningful information that will be helpful to farmers and enable sustainable farming practices. These next-generation tools can help answer a key challenge in plant biology, which is to bridge the knowledge gap between our understanding of model laboratory-grown plants and agriculturally-relevant crops cultivated in fields or production facilities.”
Early plant stress detection is key to timely intervention and increasing the effectiveness of management decisions for specific types of stress conditions in plants. The development of these tools capable of studying plant health and reporting stress events in real-time will benefit both plant biologists and farmers. The data obtained from these tools can be translated into useful information for farmers to make management decisions in real-time to prevent yield loss and reduced crop quality.
The species-independent tools also offer new study opportunities in plant science for researchers. In contrast to conventional genetic engineering techniques that are only applicable to model plants in laboratory settings, the new tools apply to any plant species which enables the study of agriculturally-relevant crops previously understudied. The adoption of these tools can enhance researchers’ basic understanding of plant science and potentially bridge the gap between model and non-model plants.
“The SMART DiSTAP interdisciplinary team facilitated the work for this paper and we have both experts in engineering new agriculture technologies and potential end-users of these technologies involved in the evaluation process,” said Professor Michael Strano, the paper’s co-corresponding author, DiSTAP co-lead Principal Investigator, and Carbon P. Dubbs Professor of Chemical Engineering at MIT. “It has been the dream of an urban farmer to continually, at all times, engineer optimal growth conditions for plants with precise inputs and tightly controlled variables. These tools open the possibility of real-time feedback control schemes that will accelerate and improve plant growth, yield, nutrition, and culinary properties by providing optimal growth conditions for plants in the future of urban farming.”
“To facilitate widespread adoption of these technologies in agriculture, we have to validate their economic potential and reliability, ensuring that they remain cost-efficient and more effective than existing approaches,” the paper’s co-corresponding author, DiSTAP co-lead Principal Investigator, and Deputy Chairman of TLL Professor Chua Nam Hai explained. “Plant nanosensors and Raman spectroscopy would allow farmers to adjust fertilizer and water usage, based on internal responses within the plant, to optimize growth, driving cost efficiencies in resource utilization. Optimal harvesting conditions may also translate into higher revenue from increased product quality that customers are willing to pay a premium for.”
Collaboration among engineers, plant biologists, and data scientists, and further testing of new tools under field conditions with critical evaluations of their technical robustness and economic potential will be important in ensuring sustainable implementation of technologies in tomorrow’s agriculture.
DiSTAP Scientific Advisory Board Members, Professor Kazuki Saito, Group Director of Metabolomics Research Group at RIKEN Center for Sustainable Resource Science, and Hebrew University of Jerusalem Professor, Oded Shoseyov also co-authored the paper.