Nanometer Precision Research Articles

Production of Organizational Chiral Structures by Design.

Organizational chirality on surfaces has been of interest in chemistry and materials science due to its scientific importance as well as its potential applications. Current methods for producing organizational chiral structures on surfaces are primarily based upon the self-assembly of molecules. While powerful, the chiral structures are restricted to those dictated by surface reaction thermodynamics. This work introduces a method to create organizational chirality by design with nanometer precision. Using atomic force microscopy-based nanolithography, in conjunction with chosen surface chemistry, various chiral structures are produced with nanometer precision, from simple spirals and arrays of nanofeatures to complex and hierarchical chiral structures. The size, geometry, and organizational chirality is achieved in deterministic fashion, with high fidelity to the designs. The concept and methodology reported here provide researchers a new and generic means to carry out organizational chiral chemistry, with the intrinsic advantages of chiral structures by design. The results open new and promising applications including enantioselective catalysis, separation, and crystallization, as well as optical devices requiring specific polarized radiation and fabrication and recognition of chiral nanomaterials.

Multiple Wavelength Photopolymerization of Stable Poly(Catecholamines)-DNA Origami Nanostructures.

The synthesis of multicomponent polymer hybrids with nanometer precision is chemically challenging in the bottom‐up synthesis of complex nanostructures. Here, we leverage the fidelity of the DNA origami technique to install a multiple wavelength responsive photopolymerization system with nanometer resolution. By precisely immobilizing various photosensitizers on the origami template, which are only activated at their respective maximum wavelength, we can control sequential polymerization processes. In particular, the triggered photosensitizers generate reactive oxygen species that in turn initiate the polymerization of the catecholamines dopamine and norepinephrine. We imprint polymeric layers at designated positions on DNA origami, which modifies the polyanionic nature of the DNA objects, thus promoting their uptake into living cells while preserving their integrity. Our herein proposed method provides a rapid platform to access complex 3D nanostructures by customizing material and biological interfaces.

Resolving plasmonic hotspots by label-free super-resolution microscopy.

The plasmonic hotspot of metal nanostructures has small dimension far beyond the optical diffraction limit. When trying to locate the hotspot using fluorescent probes, the localization is significantly distorted due to the coupling of emission and surface plasmon. A label-free technique can solve the problem, which uses hotspot emission as the native probe. We demonstrate a super-resolution microscopy investigation based on this idea. By modulating hotspot emission of crossed silver nanowires, which have a pair of plasmonic hotspots approximately 100 nm apart at the intersection, we precisely locate and separate them with nanometer precision. This label-free technique could be applied for analyzing hotspot distribution with high efficiency and precision.

Epigallocatechin gallate-loaded tetrahedral DNA nanostructures as a novel inner ear drug delivery system.

The study of drug delivery systems to the inner ear is a crucial but challenging field. The sensory organ (in the inner ear) is protected by the petrous bone labyrinth and the membranous labyrinth, both of which need to be overcome during the drug delivery process. The requirements for such a delivery system include small size, appropriate flexibility and biodegradability. DNA nanostructures, biomaterials that can arrange multiple functional components with nanometer precision, exhibit characteristics that are compatible with the requirements for inner ear drug delivery. Herein, we report the development of a novel inner ear drug delivery system based on epigallocatechin gallate (EGCG)-loaded tetrahedral DNA nanostructures (TDNs, EGCG@TDNs). The TDNs self-assembled via base-pairing of four single-stranded DNA constructs and EGCG was loaded into the TDNs through non-covalent interactions. Cy5-labeled TDNs (Cy5-TDNs) were significantly internalized by the House Ear Institute-Organ of Corti 1 cell line, and this endocytosis was energy-, clathrin-, and micropinocytosis-dependent. Cy5-TDNs penetrated the round window membrane (RWM) rapidly in vivo. Local application of EGCG@TDNs onto the RWM of guinea pigs in a single dose continuously released EGCG over 4 hours. Drug concentrations in the perilymph were significantly elevated compared with the administration of free EGCG at the same dose. EGCG@TDNs were found to have favorable biocompatibility and strongly affected the RSL3-induced down-regulation of GPX4 and the generation of reactive oxygen species, on the basis of 2',7'-dichlorodihydrofluorescein diacetate staining. JC-1 staining suggested that EGCG@TDNs successfully reversed the decrease in mitochondrial membrane potential induced by RSL-3 in vitro and rescued cells from apoptosis, as demonstrated by the analysis of Annexin V-FITC/PI staining. Further functional studies showed that a locally administered single-dose of EGCG@TDNs effectively preserved spiral ganglion cells in C57/BL6 mice after noise-induced hearing loss. Hearing loss at 5.6 and 8 kHz frequencies was significantly attenuated when compared with the control EGCG formulation. Histological analyses indicated that the administration of TDNs and EGCG@TDNs did not induce local inflammatory responses. These favorable histological and functional effects resulting from the delivery of EGCG by TDNs through a local intratympanic injection suggest potential for therapeutic benefit in clinical applications.

Optical Detection for the Adsorption Kinetics of Surfactant Solutions on the Surface/Interface: Oblique-Incidence Reflectivity Difference Investigation

The interaction of interfacial molecules was a hot issue in many fields, such as petroleum: the adsorption kinetics process of surfactant molecules on the interface was the key to reduce the dynamic interfacial tension and enhance oil recovery. Since the aggregation behavior of surfactant molecules on the water surface would lead to changes in the dielectric properties of the surface layer, we applied a dielectric detection technology with a vertical resolution of nanometer precision, oblique-incidence reflectivity difference (OIRD) technology, to study the adsorption kinetics of surfactant molecules on the water surface in this article. According to the test results, we established a model of molecular dynamic adsorption and explained its mechanism. This dynamic process could be divided into three stages: micelles dissociated in bulk water, molecules diffused to the subsurface layer, and molecules broke through the adsorption barrier and adsorbed on the water surface. Among them, the diffusion process was in accordance with Fick’s second law, and the process of surfactant molecules being adsorbed from the subsurface to the surface can be described by the Arrhenius formula. This work was not only applicable to the petroleum field to understand the essence of surfactant reducing surface tension but also to help investigate the subject of molecular behavior at the liquid–liquid or gas–liquid interface in other fields.

Long range dynamic displacement: precision PGC with sub-nanometer resolution in an LWSM interferometer

We propose a precision phase-generated-carrier (PGC) demodulation method with sub-nanometer resolution that avoids nonlinear errors in a laser wavelength sinusoidal modulation fiber-optic interferometer for long range dynamic displacement sensing. Using orthogonal detection and an AC-DC component extraction scheme, the PGC carrier phase delay (CPD) and laser intensity modulation phase delay can be obtained simultaneously to eliminate the nonlinear error from accompanied optical intensity modulation and CPD. Further, to realize long range displacement sensing, PGC phase modulation depth (PMD), determined by the laser wavelength modulation amplitude and the working distance of the interferometer, is required to maintain an optimal value during measurement, including initial position and dynamic movement. By combining frequency sweeping interference and modified PGC-arctan demodulation to measure real-time working distance, adaptive PMD technology is realized based on proportion control. We construct a fiber-optic Michelson and SIOS commercial interferometer for comparison and perform experiments to verify the feasibility of the proposed method. Experimental results demonstrate that an interferometer with sub-nanometer resolution and nanometer precision over a large range of 400 mm can be realized.

Heterogeneously Integrated Photonic Chip on Lithium Niobate Thin-Film Waveguide

Lithium niobate thin film represents as an ideal material substrate for quantum photonics due to its strong electro-optic effect and high-speed modulation capability. Here, we propose a novel platform which heterogeneously integrates single self-assembled InAs/GaAs quantum dots for a single-photon source on a lithium niobate photonic chip. The InAs/GaAs quantum dots can be transferred to the lithium niobate waveguide via a substrate transfer procedure with nanometer precision and be integrated through van der Waals force. A down-tapered structure is designed and optimized to deliver the photon flux generated from the InAs quantum dots embedded in a GaAs waveguide to the lithium niobate waveguide with an overall efficiency of 42%. In addition, the electro-optical effect is used to tune, and therefore to tune the beam splitting ratio of the integrated lithium niobate directional coupler, which can simultaneously route multiple photons to different spatial modes, and subsequently fan out through grating couplers to achieve single-photon sub-multiplexing. The proposed device opens up novel opportunities for achieving multifunctional hybrid integrated photonic chips.

Study on rapid convergence strategy of nano-precision optical surface by ion beam figuring

Ion beam figuring (IBF) provides a deterministic figuring method for fabricating ultra-high precision optical components such as lithographic objective lenses. But in the previous IBF process, the convergence of surface accuracy is often uncertain. Therefore, the iterative processing methods are mostly adopted. In the iterative process, the convergence ratio (the ratio of root mean square before and after figuring) of single figuring is relatively low. With the improvement of machining accuracy, the convergence ratio continues to decrease. The study analyzes the factors that limit the convergence ratio of single processing and the influence form and degree of each element on the convergence ratio. Furthermore, we present an IBF strategy with a high convergence ratio based on an optimized removal function. Based on this strategy, we complete the figuring experiment. The convergence ratio is much higher than the previous level. Compared with the surface of iterative figuring, the surface is simple and more favorable to figuring to sub-nanometer precision. The experimental results show that we can optimize the removal function to achieve rapid optical surface fabrication with nanometer precision.

Whispering Gallery‐Mode Microdroplet Tensiometry

Droplets are ideally suited to support high‐Q‐factor whispering gallery modes (WGMs) due to their perfectly smooth surface. WGMs enable extremely precise measurements of the droplet properties such as size and shape. Herein, a simple, fast, and very precise technique to measure interfacial tension (IFT) between two immiscible liquids based on WGMs is demonstrated. A microdroplet is generated at the end of a glass microcapillary, submerged in a continuous liquid phase, and its size changes are monitored with nanometer precision via WGMs, while simultaneously applying finely tunable pressure through the microcapillary. IFT is determined from the size of the droplet and the pressure in the microcapillary at equilibrium. Droplets as small as 8 μm are used, thus requiring extremely small sample volume. The IFT measurements can be carried out also at nonequilibrium state when either the size of the droplet or the chemical composition of the continuous phase changes in time. Simultaneously, the WGMs enable very precise measurement of the refractive index of either the droplet or the continuous phase.

Damage Control of Ultra-Thin YAG Crystal in Nano-Machining Process

Yttrium aluminum garnet (YAG) crystal is one of the most widely used laser crystals because of its excellent properties. Thin disk laser with ultra-thin YAG crystal as gain medium is widely used in micromachining, imaging, military, medical, scientific research, and so on. Ultra-thin crystals with nanometer precision surface quality are easily damaged in nano-machining process. From the fracture mechanics, the critical fracture stress of ultra-thin YAG crystal was analyzed. The model of ultra-thin YAG crystal in chemical mechanical polishing (CMP) process, one of important nano-machining technologies, was established, and the effect of sticking mode and pressure on the stress magnitude and distribution of crystal were investigated. It was confirmed that the damage phenomenon in CMP process can be effectively controlled by using the edge padding sticking method. The optimized process parameters are as follows: the pressure should be less than 65 kPa, the optimized size of the edge pad crystal for YAG crystal with 10 mm × 10 mm is 10 mm × 20 mm, and the right-angle damage limit of the edge padding crystal is 3 mm. Finally, the optimization results were experimentally verified and the high-efficiency and high-quality nano-machining of ultra-thin YAG crystal with surface roughness S a 2.85 nm and the thickness 0.175 mm was achieved.

Analysis of GRACE Follow-On Laser Ranging Interferometer Derived Inter-Satellite Pointing Angles

Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) was launched on May 22, 2018. It carries the Laser Ranging Interferometer (LRI) as a technology demonstrator that measures the inter-satellite range with nanometer precision using a laser-link between satellites. To maintain the laser-link between satellites, the LRI uses the beam steering method: a Fast Steering Mirror (FSM) is actuated to correct for misalignment between the incoming and outgoing laser beams. From the FSM commands, we can compute the inter-satellite pitch and yaw angles. These angles provide information about the spacecraft's relative orientation with respect to line-of-sight (LOS). We analyze LRI derived inter-satellite pointing angles for 2019 and 2020. Further, we present its comparison with the pointing angles derived from GRACE-FO SCA1B data, which represents the spacecraft attitude computed from star cameras and Inertial Measurement Unit (IMU) data using a Kalman filter. We discuss the correlations seen between the laser based attitude data and the spacecraft temperature variations. This analysis serves as the basis to explore the potential of this new attitude product obtained from the Differential Wavefront Sensing (DWS) control of a FSM.

Copper oxide phases probed via plasmonic light emission in the STM

Luminescence spectroscopy with a scanning tunnelling microscope (STM) is employed to differentiate bulk-type Cu2O from a Cu3O2 surface oxide at the nanometre scale. Although plasmonic modes in the tunnelling gap are responsible for the emission response in both cases, the luminescence cross-section shows a characteristic dependence on bias voltage for the two oxide phases. On the Cu3O2 surface oxide, the emission yield peaks at the 1st field emission resonance of the STM junction, when particularly high inelastic tunnelling rates are realized between tip and sample. On Cu2O(111) patches, on the other hand, direct and defect-mediated electron recombination from the oxide conduction to the valence band is responsible for plasmon excitations in the STM cavity. Given the different excitation mechanisms, Cu2O and Cu3O2 oxide regions become distinguishable in bias-dependent STM luminescence maps with nanometre precision. We expect this optical contrast scheme to be applicable whenever blends of dielectric materials with different band gaps coexist on the surface.

Strategies for the Site-Specific Decoration of DNA Origami Nanostructures with Functionally Intact Proteins.

DNA origami structures provide flexible scaffolds for the organization of single biomolecules with nanometer precision. While they find increasing use for a variety of biological applications, the functionalization with proteins at defined stoichiometry, high yield, and under preservation of protein function remains challenging. In this study, we applied single molecule fluorescence microscopy in combination with a cell biological functional assay to systematically evaluate different strategies for the site-specific decoration of DNA origami structures, focusing on efficiency, stoichiometry, and protein functionality. Using an activating ligand of the T-cell receptor (TCR) as the protein of interest, we found that two commonly used methodologies underperformed with regard to stoichiometry and protein functionality. While strategies employing tetravalent wildtype streptavidin for coupling of a biotinylated TCR-ligand yielded mixed populations of DNA origami structures featuring up to three proteins, the use of divalent (dSAv) or DNA-conjugated monovalent streptavidin (mSAv) allowed for site-specific attachment of a single biotinylated TCR-ligand. The most straightforward decoration strategy, via covalent DNA conjugation, resulted in a 3-fold decrease in ligand potency, likely due to charge-mediated impairment of protein function. Replacing DNA with charge-neutral peptide nucleic acid (PNA) in a ligand conjugate emerged as the coupling strategy with the best overall performance in our study, as it produced the highest yield with no multivalent DNA origami structures and fully retained protein functionality. With our study we aim to provide guidelines for the stoichiometrically defined, site-specific functionalization of DNA origami structures with proteins of choice serving a wide range of biological applications.

One Strategy for Nanoparticle Assembly onto 1D, 2D, and 3D Polymer Micro and Nanostructures.

The integration of nanoparticles (NPs) into photonic devices and plasmonic sensors requires selective patterning of these NPs with fine control of their size, shape, and spatial positioning. In this article, we report on a general strategy to pattern different types of NPs. This strategy involves the functionalization of photopolymers before their patterning by two-photon laser writing to fabricate micro- and nanostructures that selectively attract colloidal NPs with suitable ligands, allowing their precise immobilization and organization even within complex 3D structures. Monolayers of NPs without aggregations are obtained and the surface density of NPs on the polymer surface can be controlled by changing either the time of immersion in the colloidal solution or the type of amine molecule chemically grafted on the polymer surface. Different types of NPs (gold, silver, polystyrene, iron oxide, colloidal quantum dots, and nanodiamonds) of different sizes are introduced showing a potential toward nanophotonic applications. To validate the great potential of our method, we successfully demonstrate the integration of quantum dots within a gold nanocube with high spatial resolution and nanometer precision. The promise of this hybrid nanosource of light (plasmonic/polymer/QDs) as optical nanoswitch is illustrated through photoluminescence measurements under polarized exciting light.

A High-Precision Low-Cost Analog Acceleration and Vibration Amplifier using PVDF Piezoelectric Sensors

This paper describes a high-resolution analog acceleration and vibration amplifier for use with piezoelectric polyvinylidene fluoride (PVDF) sensors. The purpose of this system is to monitor automated parts placement on integrated circuit boards. One of the problems facing production and inspection equipment is the occurrence of resonant and ambient vibrations. Even small errors can cause systems with micrometer and nanometer precision to exceed design tolerances. This work describes a method to monitor mechanical vibrations through a portable and inexpensive signal-processing unit. The system provides user-selectable gain and filtering modules that are compact and reliable. PVDF is currently used in sensing applications, and its material properties have proven very useful for sensing mechanical stress, strain, pressure, and temperature.

Nanoscale dynamics of cellulose digestion by the cellobiohydrolase TrCel7A

Understanding the mechanism by which cellulases from bacteria, fungi, and protozoans catalyze the digestion of lignocellulose is important for developing cost-effective strategies for bioethanol production. Cel7A from the fungus Trichoderma reesei is a model exoglucanase that degrades cellulose strands from their reducing ends by processively cleaving individual cellobiose units. Despite being one of the most studied cellulases, the binding and hydrolysis mechanisms of Cel7A are still debated. Here, we used single-molecule tracking to analyze the dynamics of 11,116 quantum dot-labeled TrCel7A molecules binding to and moving processively along immobilized cellulose. Individual enzyme molecules were localized with a spatial precision of a few nanometers and followed for hundreds of seconds. Most enzyme molecules bound to cellulose in a static state and dissociated without detectable movement, whereas a minority of molecules moved processively for an average distance of 39 nm at an average speed of 3.2 nm/s. These data were integrated into a three-state model in which TrCel7A molecules can bind from solution into either static or processive states and can reversibly switch between states before dissociating. From these results, we conclude that the rate-limiting step for cellulose degradation by Cel7A is the transition out of the static state, either by dissociation from the cellulose surface or by initiation of a processive run. Thus, accelerating the transition of Cel7A out of its static state is a potential avenue for improving cellulase efficiency.

A large range compliant XY nano-manipulator with active parasitic rotation rejection

There is an increasing demand to achieve manipulating operations in nanometric precision and a macro-range (over a millimeter) simultaneously. In principle, it is possible to satisfy both requirements in a compact size taking advantages of flexure-based mechanisms, whereas limitations such as the parasitic rotation, cross-axis coupling, saturation may adversely affect the motion quality in nanometric level practically. Here, we propose a novel design methodology to actively prevent parasitic rotation of XY compliant mechanisms. Further, by means of design synthesis and real-time motion control, the prototype of manipulator is fabricated, which enables large motion range (±3 mm) along each actuation axis. Experimental results demonstrate a travel range of 2 mm × 2 mm with high linearity, small cross-axis coupling (< 0.4%), and low parasitic rotation (< 6.9 μ rad over 0.5 mm × 0.5 mm motion range). Moreover, the high natural frequency (~ 60 Hz) of the manipulator facilitates it to achieve high-precision motion with tracking error < 80 nm (20 Hz sinusoids). The experimental results of the proposed nano-manipulator outperform most of the existing ones.

Utilizing the moiré deflectometry-based detection method improves the detection sensitivity for gold nanoparticles trapped by optical tweezers

Gold nanoparticles (GNPs) are very often used as handles for nanotechnological micromanipulation. In this regard, optical trapping of GNPs is of great importance, in which locating the trapped GNP within the focal spot with nanometer precision is crucial. Very recently, we have introduced a new position detection system for optical tweezers based on moiré deflectometry (MD). Here we show, both theoretically and experimentally, that an MD detection system could provide significantly larger detection sensitivity for a trapped GNP compared to that provided by conventional back focal plane (BFP) detection systems. For instance, for a trapped 200 nm GNP, the detection sensitivity provided by the MD detection method is 280% better than that provided by the BFP detection method.

Molecular ruler of the attachment organelle in Mycoplasma pneumoniae.

Length control is a fundamental requirement for molecular architecture. Even small wall-less bacteria have specially developed macro-molecular structures to support their survival. Mycoplasma pneumoniae, a human pathogen, forms a polar extension called an attachment organelle, which mediates cell division, cytadherence, and cell movement at host cell surface. This characteristic ultrastructure has a constant size of 250–300 nm, but its design principle remains unclear. In this study, we constructed several mutants by genetic manipulation to increase or decrease coiled-coil regions of HMW2, a major component protein of 200 kDa aligned in parallel along the cell axis. HMW2-engineered mutants produced both long and short attachment organelles, which we quantified by transmission electron microscopy and fluorescent microscopy with nano-meter precision. This simple design of HMW2 acting as a molecular ruler for the attachment organelle should provide an insight into bacterial cellular organization and its function for their parasitic lifestyles.

Portable Nanoplasmonic Sensor for Real-Time SARS-CoV-2 RNA Detection

Introduction Fast, accurate, and in-situ environmental detection of SARS-CoV-2, the virus which causes COVID-19, is currently an unmet challenge. The gold standard detection method, polymerase chain reaction (PCR) is highly sensitive, but requires centralized lab infrastructure, specialized training, and is time consuming (> 3 hrs. time to result) [1].Other approaches more conducive to real-time and portable sensing are in development, including electrochemical [2] and plasmonic sensors [3]. However, improvements are still needed in device portability and robustness. Here, we introduce a new nanoplasmonic sensor configuration for SARS-CoV-2 RNA detection, which leverages commercially available surface plasmon readout instrumentation [4] for portable, real-time operation. Methods The sensor is configured as a plasmonic nanoparticle on mirror (NPoM) system, formed by a gold nanoparticle attached to a gold mirror by a peptide nucleic acid (PNA) probe complementary to the target RNA sequence (Figure 1A).The PNA capture probes are conjugated to the gold nanoparticles and then attached to the gold mirror using a two-step process [5]. Simple amine-coupling is used to attach the probes to the particle first, and then onto the activated gold mirror. Particle quantification is used to determine conjugation efficacy. The PNA probes act as a spacer layer, separating the nanoparticles from the mirror by approximately 10 nm.Upon hybridization between the PNA and RNA, the nanoparticle is pulled to within approximately 7 nm of the mirror below. The electromagnetic coupling between the nanoparticle and mirror is strongly dependent on the distance between the two and is transduced with nanometer precision by a pronounced shift in the resonance dip (Figure 1B). A change in distance of 3 nm is predicted to yield a ~40 nm shift in resonance wavelength.The NPoM system can either be interrogated in reflection mode (Figure 1B inset), or by total internal reflection with oblique illumination from the back side of the gold mirror. The latter enables integration with commercially available hardware for a portable, robust detection platform. Results and Conclusion Baseline experimental SARS-CoV-2 RNA detection has been obtained using gold nanoparticles on a glass substrate (Figure 1C). Standardized positive control material including the entire RNA genome of SARS-CoV-2 was linearly diluted to clinically relevant viral loads, and spiked into buffer for testing. The nanoparticles were functionalized with PNA capture probes complementary to a CDC-approved PCR panel sequence, and, upon RNA hybridization, a change in local refractive index was transduced by a shift in the extinction spectra peak (Figure 1C). The limit of detection of this system approached clinically relevant RNA loads (100,000 copies/mL).The NPoM geometry is expected to improve sensitivity and on-chip/portable system readout, owing to the narrower resonance width (cf. Figure 1B and 1C top). It is envisioned that this integrated platform could also be applied more broadly to the detection of DNA/RNA of other pathogens of interest including other viruses and bacterial species.