arXiv subjects

Na Liu

Publications and source records attributed to Na Liu.

At least 55 records · Page 3Linked to original sources

arXiv2021

Electrically-controlled digital metasurface device for light projection displays

Light projection displays play an increasingly important role in our modern life. Core projection systems including liquid crystal displays and digital micromirror devices can impose spatial light modulation and actively shape light waves. Recently, the advent of metasurfaces has revolutionized design concepts in nanophotonics, enabling a new family of optical elements with exceptional degrees of freedom. Here, we demonstrate a light projection display technology based on optical metasurfaces, called digital metasurface device (DMSD). Each metasurface pixel in a DMSD is electrically reconfigurable with well-controlled programmability and addressability. The DMSD can not only continuously modulate the intensity of light with high contrast, but also shape the wavefront of light generated by each metasurface pixel and dynamically switch between arbitrary holographic patterns. Our approach will pave an avenue towards the development of customized light projection devices. It will also drive the field of dynamic optical metasurfaces with fresh momentum and inspiring concepts.

physics.optics↗

arXiv2021

Dynamic Actuation of DNA-Assembled Plasmonic Nanostructures in Microfluidic Cell-Sized Compartments

Molecular motor proteins form the basis of cellular dynamics. Recently, notable efforts have led to the creation of their DNA-based mimics, which can carry out complex nanoscale motion. However, such functional analogues have not yet been integrated or operated inside synthetic cells toward the goal of realizing artificial biological systems entirely from the bottom-up. In this Letter, we encapsulate and actuate DNA-assembled dynamic nanostructures inside cell-sized microfluidic compartments. These encapsulated DNA nanostructures not only exhibit structural reconfigurability owing to their pH-sensitive molecular switches upon external stimuli but also possess optical feedback enabled by the integrated plasmonic probes. In particular, we demonstrate the power of microfluidic compartmentalization for achieving on-chip plasmonic enantiomer separation and substrate filtration. Our work exemplifies that the two unique tools, droplet-based microfluidics and DNA technology, offering high precision on the microscale and nanoscale, respectively, can be brought together to greatly enrich the complexity and diversity of functional synthetic systems.

physics.bio-ph↗

arXiv2021

DNA Nanotechnology Meets Nanophotonics

In the past decades, DNA has been intensely studied and exploited in different research areas of nanoscience and nanotechnology. At first glance, DNA-based nanophotonics seems to deviate quite far from the original goal of Nadrian Seeman, the founder of DNA nanotechnology, who hoped to organize biological entities using DNA in high-resolution crystals. As a matter of fact, DNA-based nanophotonics does closely follow his central spirit. That is, apart from being a genetic material for inheritance, DNA is also an ideal material for building molecular devices.

physics.bio-ph↗

arXiv2021

Dynamic plasmonic color generation enabled by functional materials

Displays are an indispensable medium to visually convey information in our daily life. Although conventional dye-based color displays have been rigorously advanced by world leading companies, critical issues still remain. For instance, color fading and wavelength-limited resolution restrict further developments. Plasmonic colors emerging from resonant interactions between light and metallic nanostructures can overcome these restrictions. With dynamic characteristics enabled by functional materials, dynamic plasmonic coloration may find a variety of applications in display technologies. In this review, we elucidate basic concepts for dynamic plasmonic color generation and highlight recent advances. In particular, we devote our review to a selection of dynamic controls endowed by functional materials, including magnesium, liquid crystals, electrochromic polymers, and phase change materials. We also discuss their performance in view of potential applications in current display technologies.

physics.optics↗

arXiv2021

DNA-Assembled Advanced Plasmonic Architectures

The interaction between light and matter can be controlled efficiently by structuring materials at a length scale shorter than the wavelength of interest. With the goal to build optical devices that operate at the nanoscale, plasmonics has established itself as a discipline, where near-field effects of electromagnetic waves created in the vicinity of metallic surfaces can give rise to a variety of novel phenomena and fascinating applications. As research on plasmonics has emerged from the optics and solid-state communities, most laboratories employ top-down lithography to implement their nanophotonic designs. In this review, we discuss the recent, successful efforts of employing self-assembled DNA nanostructures as scaffolds for creating advanced plasmonic architectures. DNA self-assembly exploits the base-pairing specificity of nucleic acid sequences and allows for the nanometer-precise organization of organic molecules but also for the arrangement of inorganic particles in space. Bottom-up self-assembly thus bypasses many of the limitations of conventional fabrication methods. As a consequence, powerful tools such as DNA origami have pushed the boundaries of nanophotonics and new ways of thinking about plasmonic designs are on the rise.

physics.optics↗

arXiv2021

Dynamic plasmonic colour display

Plasmonic colour printing based on engineered metasurfaces has revolutionized colour display science due to its unprecedented subwavelength resolution and high-density optical data storage. However, advanced plasmonic displays with novel functionalities including dynamic multicolour printing, animations, and highly secure encryption have remained in their infancy. Here we demonstrate a dynamic plasmonic colour display technique that enables all the aforementioned functionalities using catalytic magnesium metasurfaces. Controlled hydrogenation and dehydrogenation of the constituent magnesium nanoparticles, which serve as dynamic pixels, allow for plasmonic colour printing, tuning, erasing and restoration of colour. Different dynamic pixels feature distinct colour transformation kinetics, enabling plasmonic animations. Through smart material processing, information encoded on selected pixels, which are indiscernible to both optical and scanning electron microscopies, can only be read out using hydrogen as a decoding key, suggesting a new generation of information encryption and anti-counterfeiting applications.

physics.optics↗

arXiv2021

A plasmonic nanorod that walks on DNA origami

In nano-optics, a formidable challenge remains in precise transport of a single optical nano-object along a programmed and routed path toward a predefined destination. Molecular motors in living cells that can walk directionally along microtubules have been the inspiration for realizing artificial molecular walkers. Here we demonstrate an active plasmonic system, in which a plasmonic nanorod can execute directional, progressive and reverse nanoscale walking on two or three-dimensional DNA origami.Such a walker comprises an anisotropic gold nanorod as its body and discrete DNA strands as its feet. Specifically, our walker carries optical information and can in situ optically report its own walking directions and consecutive steps at nanometer accuracy, through dynamic coupling to a plasmonic stator immobilized along its walking track. Our concept will enable a variety of smart nanophotonic platforms for studying dynamic light-matter interaction, which requires controlled motion at the nanoscale well below the optical diffraction limit.

physics.bio-ph↗

arXiv2021

Chiral plasmonics

We present a comprehensive overview of chirality and its optical manifestation in plasmonic nanosystems and nanostructures. We discuss top-down fabricated structures that range from solid metallic nanostructures to groupings of metallic nanoparticles arranged in three dimensions. We also present the large variety of bottom-up synthesized structures. Using DNA, peptides, or other scaffolds, complex nanoparticle arrangements of up to hundreds of individual nanoparticles have been realized. Beyond this static picture, we also give an overview of recent demonstrations of active chiral plasmonic systems, where the chiral optical response can be controlled by an external stimulus. We discuss the prospect of using the unique properties of complex chiral plasmonic systems for enantiomeric sensing schemes.

physics.optics↗

arXiv2021

A rotary plasmonic nanoclock

One of the fundamental challenges in nanophotonics is to gain full control over nanoscale optical elements. The precise spatiotemporal arrangement determines their interactions and collective behavior. To this end, DNA nanotechnology is employed as an unprecedented tool to create nanophotonic devices with excellent spatial addressability and temporal programmability. However, most of the current DNA-assembled nanophotonic devices can only reconfigure among random or very few defined states. Here, we demonstrate a DNA-assembled rotary plasmonic nanoclock. In this system, a rotor gold nanorod can carry out directional and reversible 360 degree rotation with respect to a stator gold nanorod, transitioning among 16 well-defined configurations powered by DNA fuels. The full-turn rotation process is monitored by optical spectroscopy in real time. We further demonstrate autonomous rotation of the plasmonic nanoclock powered by DNAzyme-RNA interactions. Such assembly approaches pave a viable route towards advanced nanophotonic systems entirely from the bottom-up.

physics.app-ph↗

arXiv2021

DNA nanotechnology for building artificial dynamic systems

A fundamental design rule that nature has developed for biological machines is the intimate correlation between motion and function. One class of biological machines is molecular motors in living cells, which directly convert chemical energy into mechanical work. They coexist in every eukaryotic cell, but differ in their types of motion, the filaments they bind to, the cargos they carry, as well as the work they perform. Such natural structures offer inspiration and blueprints for constructing DNA-assembled artificial systems, which mimic their functionality. In this article, we describe two groups of cytoskeletal motors, linear and rotary motors. We discuss how their artificial analogues can be built using DNA nanotechnology. Finally, we summarize ongoing research directions and conclude that DNA origami has a bright future ahead.

physics.bio-ph↗

arXiv2021

Stabilizing $γ$-MgH$_2$ at Nanotwins in Mechanically Constrained Nanoparticles

Reversible hydrogen uptake and the metal/dielectric transition make the Mg/MgH$_2$ system a prime candidate for solid state hydrogen storage and dynamic plasmonics. However, high dehydrogenation temperatures and slow dehydrogenation hamper broad applicability. One promising strategy to improve dehydrogenation is the formation of metastable $γ$-MgH$_2$. A nanoparticle (NP) design, where $γ$-MgH$_2$ forms intrinsically during hydrogenation is presented and a formation mechanism based on transmission electron microscopy results is proposed.Volume expansion during hydrogenation causes compressive stress within the confined, anisotropic NPs, leading to plastic deformation of $β$-MgH$_2$ via (301) $β$ twinning. It is proposed that these twins nucleate $γ$-MgH$_2$ nanolamellas, which are stabilized by residual compressive stress. Understanding this mechanism is a crucial step toward cycle-stable, Mg-based dynamic plasmonic and hydrogen-storage materials with improved dehydrogenation. It is envisioned that a more general design of confined NPs utilizes the inherent volume expansion to reform $γ$-MgH$_2$ during each rehydrogenation

cond-mat.mtrl-sci↗

arXiv2021

Chiral Plasmonic Hydrogen Sensors

In this article, a chiral plasmonic hydrogen-sensing platform using palladium-based nanohelices is demonstrated. Such 3D chiral nanostructures fabricated by nanoglancing angle deposition exhibit strong circular dichroism both experimentally and theoretically. The chiroptical properties of the palladium nanohelices are altered upon hydrogen uptake and sensitively depend on the hydrogen concentration. Such properties are well suited for remote and spark-free hydrogen sensing in the flammable range. Hysteresis is reduced, when an increasing amount of gold is utilized in the palladium-gold hybrid helices. As a result, the linearity of the circular dichroism in response to hydrogen is significantly improved. The chiral plasmonic sensor scheme is of potential interest for hydrogen-sensing applications, where good linearity and high sensitivity are required.

physics.app-ph↗

arXiv2021

DNA Origami Catenanes Templated by Gold Nanoparticles

Mechanically interlocked molecules have marked a breakthrough in the field of topological chemistry and boosted the vigorous development of molecular machinery. As an archetypal example of the interlocked molecules, catenanes comprise macrocycles that are threaded through one another like links in a chain. Inspired by the transition metal-templated approach of catenanes synthesis, the hierarchical assembly of DNA origami catenanes templated by gold nanoparticles is demonstrated in this work. DNA origami catenanes, which contain two, three or four interlocked rings are successfully created. In particular, the origami rings within the individual catenanes can be set free with respect to one another by releasing the interconnecting gold nanoparticles. This work will set the basis for rich progress toward DNA-based molecular architectures with unique structural programmability and well-defined topology.

physics.bio-ph↗

arXiv2021

Magnesium for Dynamic Nanoplasmonics

The key component of nanoplasmonics is metals. For a long time, gold and silver have been the metals of choice for constructing plasmonic nanodevices because of their excellent optical properties. However, these metals possess a common characteristic, i.e., their optical responses are static. The past decade has been witnessed tremendous interest in dynamic control of the optical properties of plasmonic nanostructures. To enable dynamic functionality, several approaches have been proposed and implemented. For instance, plasmonic nanostructures can be fabricated on stretchable substrates or on programmable templates so that the interactions between the constituent metal nanoparticles and therefore the optical responses of the plasmonic systems can be dynamically changed. Also, plasmonic nanostructures can be embedded in tunable dielectric materials, taking advantage of the sensitive dependence of the localized surface plasmon resonances on the neighboring environment. Another approach, which is probably the most intriguing one, is to directly regulate the carrier densities and dielectric functions of the metals themselves.

physics.optics↗

arXiv2021

A Reusable Metasurface Template

Metasurfaces have revolutionized the design concepts for opticalcomponents, fostering an excitingfield offlat optics. Thanks to theflat and ultrathinnature, metasurfaces possess unique advantages over conventional optical components,such as lightweight, high compatibility, among others. To comply with potential appli-cations, further research endeavors need to be exerted for advancing the reusability andpracticality of metasurfaces. In this work, we demonstrate a reusable template approachto achieve optical multifunctionality with metasurfaces, utilizing both the geometric andpropagation phases to shape light waves. In principle, such a metasurface template can beemployed infinite times to enable a large variety of optical functions. As proof-of-conceptexperiments, we demonstrate metalensing, holography, and vortex beam shaping. Ourwork will leverage the high scalability aspects of metasurface devices for practical applications.

physics.optics↗

arXiv2021

Dynamic Janus Metasurfaces in the Visible Spectral Region

Janus monolayers have long been captivated as a popular notion for breaking in-plane and out-of-plane structural symmetry. Originated from chemistry and materials science, the concept of Janus functions have been recently extended to ultrathin metasurfaces by arranging meta-atoms asymmetrically with respect to the propagation or polarization direction of the incident light. However, such metasurfaces are intrinsically static and the information they carry can be straightforwardly decrypted by scanning the incident light directions and polarization states once the devices are fabricated. In this Letter, we present a dynamic Janus metasurface scheme in the visible spectral region. In each super unit cell, three plasmonic pixels are categorized into two sets. One set contains a magnesium nanorod and a gold nanorod that are orthogonally oriented with respect to each other, working as counter pixels. The other set only contains a magnesium nanorod. The effective pixels on the Janus metasurface can be reversibly regulated by hydrogenation/dehydrogenation of the magnesium nanorods. Such dynamic controllability at visible frequencies allows for flat optical elements with novel functionalities including beam steering, bifocal lensing, holographic encryption, and dual optical function switching.

physics.optics↗

arXiv2021

Dynamic Plasmonic System That Responds to Thermal and Aptamer-Target Regulations

The DNA origami technique has empowered a new paradigm in plasmonics for manipulating light and matter at the nanoscale. This interdisciplinary field has witnessed vigorous growth, outlining a viable route to construct advanced plasmonic architectures with tailored optical properties. However, so far plasmonic systems templated by DNA origami have been restricted to respond to only single stimuli. Despite broad interest and scientific importance, thermal and aptamer-target regulations have not yet been widely utilized to reconfigure three-dimensional plasmonic architectures. In this Letter, we demonstrate a chiral plasmonic nanosystem integrated with split aptamers, which can respond to both thermal and aptamer-target regulations. We show that our dual-responsive system can be noninvasively tuned in a wide range of temperatures, readily correlating thermal control with optical signal changes. Meanwhile, our system can detect specific targets including adenosine triphosphate and cocaine molecules, which further enhance the optical response modulations and in turn influence the thermal tunability.

physics.app-ph↗

arXiv2021

DNA-Assembled Multilayer Sliding Nanosystems

DNA nanotechnology allows for the realization of complex nanoarchitectures in which the spatial arrangements of different constituents and most functions can be enabled by DNA. When optically active components are integrated in such systems, the resulting nanoarchitectures not only provide great insights into the self-assembly of nanoscale elements in a systematic way but also impart tailored optical functionality to DNA origami. In this Letter, we demonstrate DNA-assembled multilayer nanosystems, which can carry out coordinated and reversible sliding motion powered by DNA fuels. Gold nanoparticles cross-link DNA origami filaments to define the configurations of the multilayer nanoarchitectures as well as to mediate relative sliding between the neighboring origami filaments. Meanwhile, the gold nanoparticles serve as optical probes to dynamically interact with the fluorophores tethered on the filaments, rendering in situ detection of the stepwise sliding processes possible. This work seeds the basis to implement DNA-assembled complex optical nanoarchitectures with programmability and addressability, advancing the field with new momentum.

physics.bio-ph↗