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Feb 23, 2024

Dynamic light manipulation via silicon-organic slot metasurfaces

Posted by in categories: chemistry, computing, nanotechnology

Relying on sub-wavelength nanostructures, metasurfaces have been shown as promising candidates for replacing conventional free-space optical components by arbitrarily manipulating the amplitude, phase, and polarization of optical wavefronts in certain applications1,2,3. In recent years, the scope of their applications has been expanded towards complete spatio-temporal control through the introduction of active metasurfaces. These developments open up exciting new possibilities for dynamic holography4, faster spatial light modulators5, and fast optical beam steering for LiDAR6. Large efforts have been channeled into various modulation mechanisms7. Microelectromechanical and nanoelectromechanical systems (MEMS and NEMS)8,9,10,11 have the advantages of low-cost and CMOS-compatibility, but the speed is limited up to MHz. Phase-change materials12,13,14 have fast, drastic, and non-volatile refractive index change, but lack continuous refractive index tuning and have a limited number of cycles constraining applicability to reconfigurable devices. Through molecule reorientation, liquid crystal can have index modulation over 10%, while under relatively low applied voltages Tunable liquid crystal metasurfaces, U.S. patent number 10,665,953 [Application Number 16/505,687]15. Techniques of liquid crystal integration have also advanced after decades of development. However, the tuning speeds are limited to kHz range16. Thermal-optic effects can induce relatively large refractive index changes17,18, but the speed is inherently limited and the on-chip thermal management can be challenging. The co-integration of transparent conductive oxide and metallic plasmonic structures5,6 has been demonstrated in epsilon-near-zero (ENZ) regime to control the wavefront of reflected light, but the low reflection amplitude induced by the optical loss of the materials and the ENZ regime is unavoidable.

In modern photonics, a multitude of technologies for tunable optics and frequency conversion19,20 are realized with nonlinear materials that have low loss and a strong χ effect, such as lithium niobate21,22, aluminum nitride23, and organic electro-optic (OEO) materials24. Their ultrafast responses make it possible to use RF or millimeter-wave control25. Developments in computational chemistry have also led to artificially engineered organic molecules that have record-high nonlinear coefficients with long-term and high-temperature stability26,27. However, their potential in modifying free-space light has been relatively unexplored until recently. Several OEO material-hybrid designs have demonstrated improved tunability of metasurfaces28,29,30. Utilizing dielectric resonant structures and RF-compatible coplanar waveguides, a free-space silicon-organic modulator has recently accomplished GHz modulation speed31. However, all demonstrations to date require high operating voltages ± 60V, due to low resonance tuning capability (frequency shift / voltage), which hinders their integration with electronic chips.

In this work, we propose combining high-Q metasurfaces based on slot-mode resonances with the unique nano-fabrication techniques enabled by OEO materials, which drastically reduces the operating voltage. The low voltage is mainly achieved from the ability to place the electrodes in close proximity to each other while hosting high-Q modes in between and the large overlap of the optical and RF fields in OEO materials. In the following sections, we first provide the design concepts and considerations for achieving a reduced operating voltage. Next, we numerically demonstrate the advantage of a particular selected mode compared to other supported modes in the structure. Finally, we experimentally realize our concepts and characterize the performance of the electro-optic metasurface.

Feb 23, 2024

All-atom RNA structure determination from cryo-EM maps

Posted by in categories: mapping, particle physics, robotics/AI

RNA structures are built from cryogenic electron microscopy maps using deep learning and backbone tracing.

Feb 23, 2024

Angle-resolved transport non-reciprocity and spontaneous symmetry breaking in twisted trilayer graphene

Posted by in category: materials

Angle-resolved transport measurements on twisted trilayer graphene reveal evidence for a variety of correlated states with spontaneous symmetry breaking, and offer evidence of momentum polarization.

Feb 23, 2024

Researchers harness 2D magnetic materials for energy-efficient computing

Posted by in categories: computing, materials

MIT researchers used ultrathin van der Waals materials to create an electron magnet that can be switched at room temperature. This type of magnet could be used to build magnetic processors or memories that would consume far less energy than silicon devices.

Feb 23, 2024

Korea University study explores a novel and precise mitochondrial gene editing method

Posted by in categories: bioengineering, biotech/medical, genetics

Gene editing technology could revolutionize the treatment of genetic diseases, including those that affect the mitochondria—cell structures that generate the energy required for the proper functioning of living cells in all individuals. Abnormalities in the mitochondrial DNA (mtDNA) could lead to mitochondrial genetic diseases.

Targeted base editing of mammalian mtDNA is a powerful technology for modeling mitochondrial genetic diseases and developing potential therapies. Programmable deaminases, which consist of a custom DNA-binding protein and a nucleobase deaminase, enable precise mtDNA editing.

There are two types of programmable deaminases for genome editing: cytosine base editors and adenine base editors, such as DddA-derived cytosine base editors (DdCBEs) and transcription activator-like effector (TALE)-linked deaminases (TALEDs). These editors bind to specific DNA sites in the mitochondrial genome and convert bases, resulting in targeted cytosine-to-thymine (C-to-T) or adenine-to-guanine (A-to-G) conversions during DNA replication or repair. However, the current gene editing approaches have many limitations, including thousands of off-target A-to-G edits while using TALEDs.

Feb 23, 2024

NIH Common Fund Somatic Cell Genome Editing Program (Audio Described)

Posted by in categories: biotech/medical, futurism

For more information on the Somatic Cell Genome Editing program, visit our website at: https://commonfund.nih.gov/editing Follow this link to for a version of the video that does not include audio descriptions: • NIH Common Fund Somatic Cell Genome E… Thousands of human diseases are caused by changes, or mutations, to the body’s DNA. What if we could treat all these diseases by diving into our living cells to correct the mistakes? The Somatic Cell Genome Editing program aims to make that happen. Recently, researchers have made great progress in correcting DNA mutations using a technique called genome editing, and the first tests of genome editing for human diseases are starting. However, there are still some challenges to achieve safe and effective genome editing in patient cells. The Somatic Cell Genome Editing, or SCGE, program was launched by the NIH Common Fund to develop quality tools to perform safe and effective genome editing in human patients. The SCGE program will make more genome editing tools available to researchers to develop better packages to deliver the tools to the right cells, design new tests for the safety and efficacy of genome editing, and make all of the information available to the scientific community to drive future discoveries and cures for patients.

Feb 23, 2024

Artificial intelligence needs a scientific method-driven reset

Posted by in category: robotics/AI

AI needs to develop more solid assumptions, falsifiable hypotheses, and rigorous experimentation.

Feb 23, 2024

Ask Ethan: Is it possible that gravity isn’t quantum?

Posted by in category: quantum physics

For generations, physicists have been searching for a quantum theory of gravity. But what if gravity isn’t actually quantum at all?

Feb 23, 2024

Why string theory has been unfairly maligned

Posted by in categories: particle physics, quantum physics

String theory is widely considered beyond empirical investigation. But we could conceivably test it thanks to ancient particles called moduli, which might appear in astronomical observations, says theorist Joseph Conlon.

By Thomas Lewton

Feb 23, 2024

Scientists closer to solving mysteries of universe after measuring gravity in quantum world

Posted by in category: quantum physics

Scientists are a step closer to unravelling the mysterious forces of the universe after working out how to measure gravity on a microscopic level.

Experts have never fully understood how the force which was discovered by Isaac Newton works in the tiny quantum world.

Even Einstein was baffled by quantum gravity and, in his theory of general relativity, said there is no realistic experiment which could show a quantum version of gravity.

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