Manipulation Of Nanoparticles Research Articles

Enhanced trapping properties of coupled plasmonic tweezers via plasmon-exciton interaction

Excited plasmonic nanoantennas enable the manipulation of photons coupled with quantum emitters or the trapping of particles as plasmonic tweezers, leveraging the strong evanescent gradient fields at the nanoscale. However, the ohmic loss of metals presents a significant challenge for the stable and high-precision manipulation of nanoparticles without causing damage. In this study, we investigated the enhanced trapping properties induced by plasmon-exciton interaction for coupled plasmonic tweezers. Through the coupling between plasmons and excitons, dynamic particle trapping is achievable under low excitation power conditions of 0.45 mW, with the trapping stiffness increasing by nearly 20 times. Furthermore, the trapping stiffness can be fine-tuned by modulating the quantity of excitons to regulate the coupling strength. Coupled plasmonic tweezers offer an effective strategy to mitigate the influence of ohmic loss on trapping performance, by manipulating particles with minimal laser power. These findings provide insights into enhancing trapping performance through plasmon-exciton coupling, with potential applications in biomedicine and quantum information science.

Fresnel lens three-dimensionally printed on the facet of a single mode fiber for trapping, manipulation, and spectrum.

Fiber optical tweezers (FOTs) provide a functionality for micro-/nanoparticle manipulation with a slim and flexible optical fiber setup. An added in situ spectroscopic functionality can achieve characterization of the trapped particle, potentially useful for endoscopic, in-vivo studies in an inherently heterogeneous environment if the applicator end is all-fiber-built. Here, we demonstrate all-fiber optical tweezers (a-FOTs) for the trapping and in situ spectral measurement of a single, cell-sized microparticle. The key to ensure the simultaneous bifunctionality is a high numerical aperture (NA) Fresnel lens fabricated by two-photon direct laser writing (DLW) corrected by grid-correction methods. We demonstrate trapping and time-resolved, in situ spectroscopy of a single upconversion particle (UCP), a common fluorescent biomarker in biophotonics. The system achieves a 0.5-s time resolution in the in situ spectral measurement of a trapped UCP. The all-fiber designed system preserves the advantages of flexibility and robustness of the fiber, potentially useful for in-vivo biomedical studies such as cell-to-cell interactions, pH and temperature detection, and nucleic acids detection.

Acoustofluidic manipulation for submicron to nanoparticles.

Particles, ranging from submicron to nanometer scale, can be broadly categorized into biological and non-biological types. Submicron-to-nanoscale bioparticles include various bacteria, viruses, liposomes, and exosomes. Non-biological particles cover various inorganic, metallic, and carbon-based particles. The effective manipulation of these submicron to nanoparticles, including their separation, sorting, enrichment, assembly, trapping, and transport, is a fundamental requirement for different applications. Acoustofluidics, owing to their distinct advantages, have emerged as a potent tool for nanoparticle manipulation over the past decade. Although recent literature reviews have encapsulated the evolution of acoustofluidic technology, there is a paucity of reports specifically addressing the acoustical manipulation of submicron to nanoparticles. This article endeavors to provide a comprehensive study of this topic, delving into the principles, apparatus, and merits of acoustofluidic manipulation of submicron to nanoparticles, and discussing the state-of-the-art developments in this technology. The discourse commences with an introduction to the fundamental theory of acoustofluidic control and the forces involved in nanoparticle manipulation. Subsequently, the working mechanism of acoustofluidic manipulation of submicron to nanoparticles is dissected into two parts, dominated by the acoustic wave field and the acoustic streaming field. A critical analysis of the advantages and limitations of different acoustofluidic platforms in nanoparticles control is presented. The article concludes with a summary of the challenges acoustofluidics face in the realm of nanoparticle manipulation and analysis, and a forecast of future development prospects.

Gradient-induced long-range optical pulling force based on photonic band gap

Optical pulling provides a new degree of freedom in optical manipulation. It is generally believed that long-range optical pulling forces cannot be generated by the gradient of the incident field. Here, we theoretically propose and numerically demonstrate the realization of a long-range optical pulling force stemming from a self-induced gradient field in the manipulated object. In analogy to potential barriers in quantum tunnelling, we use a photonic band gap design in order to obtain the intensity gradients inside a manipulated object placed in a photonic crystal waveguide, thereby achieving a pulling force. Unlike the usual scattering-type optical pulling forces, the proposed gradient-field approach does not require precise elimination of the reflection from the manipulated objects. In particular, the Einstein-Laub formalism is applied to design this unconventional gradient force. The magnitude of the force can be enhanced by a factor of up to 50 at the optical resonance of the manipulated object in the waveguide, making it insensitive to absorption. The developed approach helps to break the limitation of scattering forces to obtain long-range optical pulling for manipulation and sorting of nanoparticles and other nano-objects. The developed principle of using the band gap to obtain a pulling force may also be applied to other types of waves, such as acoustic or water waves, which are important for numerous applications.

Ultracompact Lab-on-a-Chip Device for Surface-Enhanced Coherent Anti-Stokes Raman Scattering.

This paper introduces an ultracompact lab-on-a-chip device with a size of [Formula: see text] for surface-enhanced coherent anti-Stokes Raman scattering. This device comprises of a unique hybrid plasmonic-photonic vertical coupler, for light-coupling between the device and a light source, and a heptamer plasmonic nanotweezer for trapping and manipulation of nanoparticles. The coupler with its nanoscale size of [Formula: see text] offers maximum coupling efficiency and directivity of -4.2 dB and 17.8 dB with a 3 dB bandwidth across the wavelength range of [Formula: see text]. Based on a finite element method, it is theoretically shown that the tear-drop based nanotweezer can empower the device to yield a very high Raman gain of ≥ 1017 , making the detection at the single-molecule level possible. The proposed device can exhibit low damage to bioparticles through the use of near infrared wavelengths range with lower energy photons. Due to its short optical path, this device is expected to improve the Raman signal to noise ratio by reducing the level of background in-coherent Raman signals. Finally, thanks to its configuration, this device can enable the creation of parallel measurement channels, paving the way toward the development of high-throughput and mass-produced biosensors.

Nanoparticle manipulation and sorting by phased modulated interference pattern of Gaussian Evanescent Waves

The utilization of Gaussian Evanescent Waves (GEWs) in particle manipulation provides a three-dimensional force distribution that is significantly high at the vicinity of the surface and exponentially decreases as one moves away, hence enabling 3D particle manipulation, unlike plane waves. By coherently interfering four GEWs in various phase combinations, symmetric evanescent field distributions can be obtained, which allows the manipulation of nanoparticles for many applications. With the simulation we conducted, the dynamics of various-sized spherical silicon particles in a continuously flowing liquid setup have been investigated. We present the optimal phase-delayed configurations for trapping, sorting, separating, and rotating the particles.

Efficient and Shape-Sensitive Manipulation of Nanoparticles by Quasi-Bound States in the Continuum Modes in All-Dielectric Metasurfaces.

Current optical tweezering techniques are actively employed in the manipulation of nanoparticles, e.g., biomedical cells. However, there is still huge room for improving the efficiency of manipulating multiple nanoparticles of the same composition but different shapes. In this study, we designed an array of high-index all-dielectric disk antennas, each with an asymmetric open slot for such applications. Compared with the plasmonic counterparts, this all-dielectric metasurface has no dissipation loss and, thus, circumvents the Joule heating problem of plasmonic antennas. Furthermore, the asymmetry-induced excitation of quasi-bound states in continuum (QBIC) mode with a low-power intensity (1 mW/µm2) incidence imposes an optical gradient force of -0.31 pN on 8 nm radius nanospheres, which is four orders of magnitude stronger than that provided by the Fano resonance in plasmonic antenna arrays, and three orders of magnitude stronger than that by the Mie resonance in the same metasurface without any slot, respectively. This asymmetry also leads to the generation of large optical moments. At the QBIC resonance wavelength, a value of 88.3 pN-nm will act on the nanorods to generate a rotational force along the direction within the disk surface but perpendicular to the slot. This will allow only nanospheres but prevent the nanorods from accurately entering into the slots, realizing effective sieving between the nanoparticles of the two shapes.

Numerical studies of manipulation and separation of microparticles in ODEP-based microfluidic chips.

A novel optical-induced dielectrophoresis (ODEP) method employing a pressure-driven flow for the continuous separation of microparticles is presented in this study. By applying alternate current electric field on conductive indium tin oxide substrate and projecting the light geometry into the photoconductive layer, an inhomogeneous electric field is locally induced. The particles experience the dielectrophoretic force when passing through the lighting area, where the strongest electrical field gradient exists. By optimizing the structure of the lighting pattern, a stronger nonuniform electric field gradient is generated which predicts the separation of 1 and 3µm polystyrene particles. Moreover, the effects of key parameters, including the light pattern geometry, applied voltage, and flow rate, were investigated in this study, leading to the successful sorting of 700nm and 1µm particles. To further examine the separation sensitivity and practicability of the proposed ODEP microfluidic method, the isolation of two different types of circulating tumor cells from T-cells and red blood cells are demonstrated, providing a novel method for the manipulation and separation of microparticles and nanoparticles.

Surface recoil force on dielectric nanoparticle enhancement via graphene acoustic surface plasmon excitation: non-local effect consideration.

Controlling optomechanical interactions at sub-wavelength levels is of great importance in academic science and nanoparticle manipulation technologies. This Letter focuses on the improvement of the recoil force on nanoparticles placed close to a graphene-dielectric-metal structure. The momentum conservation involving the non-symmetric excitation of acoustic surface plasmons (ASPs), via near-field circularly polarized dipolar scattering, implies the occurrence of a huge momentum kick on the nanoparticle. Owing to the high wave vector values entailed in the near-field scattering process, it has been necessary to consider the non-locality of the graphene electrical conductivity to explore the influence of the scattering loss on this large wave vector region, which is neglected by the semiclassical model. Surprisingly, the contribution of ASPs to the recoil force is negligibly modified when the non-local effects are incorporated through the graphene conductivity. On the contrary, our results show that the contribution of the non-local scattering loss to this force becomes dominant when the particle is placed very close to the graphene sheet and that it is mostly independent of the dielectric thickness layer. Our work can be helpful for designing new and better performing large plasmon momentum optomechanical structures using scattering highly dependent on the polarization for moving dielectric nanoparticles.

Force analysis and distribution evolution of Fe3O4 nanoparticles in magnetic fluids

The effective utilization of magnetic nanoparticles in ferromagnetic fluids relies on their distribution and properties, which can be influenced by their arrangement at both micro and macro scales. In this paper, we present a dynamic model to analyze the motion and forces of nanoparticles in magnetic fluids, aiming to describe their distribution evolution under magnetic and flow fields. Finite element simulations using COMSOL software are employed, and a dimensionless ordering coefficient is proposed to quantitatively evaluate the status of nanoparticle distribution. The results indicate that reducing fluid viscosity, increasing magnetic field strength, and increasing magnetic particle radius can facilitate the attainment of an optimal ordered state for nanoparticles in magnetic fluids. However, prolonged exposure to a magnetic field can lead to particle agglomeration, hindering the effective manipulation of nanoparticles. To mitigate rapid agglomeration, we employ an intermittent magnetic field exposure strategy during the curing process of a magnetic slurry consisting of PVDF, DMF, and Fe3O4 nanoparticles. The tests reveal that with increasing magnetic field exposure time, the increase rate of the ordering coefficient initially progresses slowly, then gradually accelerates, and eventually reaches equilibrium. This approach successfully addresses the rapid agglomeration of magnetic particles observed in the simulation results. Consequently, precise control over the nanoparticle radius, magnetic field strength, and carrier fluid viscosity allows for meticulous regulation of the ordered distribution state of magnetic particles. This breakthrough has significant potential in expanding the application and research opportunities of magnetic materials.

Irrotational flow analysis of Rayleigh-Taylor instability in nanofluid layer with tangential magnetic field

The application of nanofluids in the presence of a magnetic field holds promise for advanced drug delivery systems, where controlled manipulation of magnetic nanoparticles within nanofluids can enhance targeted and localized drug delivery. This study explores the instability of a viscous fluid-nanofluid interface arranged in a planar configuration influenced by a tangential magnetic field using the irrotational flow theory. When the nanofluid is positioned above a viscous fluid, the interface is susceptible to the Rayleigh-Taylor instability. Employing linear stability theory, an explicit relationship connecting the perturbation growth parameter with the wavenumber is derived. Different dimensionless quantities such as the Atwood number, Weber number, Froude number, and Reynolds number are analyzed using stability plots. These plots provide valuable information about the behavior of interfaces. Increased magnetic field strength is observed to delay instability onset. Surface tension is found to stabilize the interface, whereas inertial forces destabilize it. This investigation contributes to understanding and controlling the interface dynamics in nanofluid systems.

Highly-Adaptable Optothermal Nanotweezers for Trapping, Sorting, and Assembling across Diverse Nanoparticles.

Optical manipulation of various kinds of nanoparticles is vital in biomedical engineering. However, classical optical approaches demand higher laser power and are constrained by diffraction limits, necessitating tailored trapping schemes for specific nanoparticles. They lack a universal and biocompatible tool to manipulate nanoparticles of diverse sizes, charges, and materials. Through precise modulation of diffusiophoresis and thermo-osmotic flows in the boundary layer of an optothermal-responsive gold film, highly adaptable optothermal nanotweezers (HAONTs) capable of manipulating a single nanoparticle as small as sub-10nm are designed. Additionally, a novel optothermal doughnut-shaped vortex (DSV) trapping strategy is introduced, enabling a new mode of physical interaction between cells and nanoparticles. Furthermore, this versatile approach allows for the manipulation of nanoparticles in organic, inorganic, and biological forms. It also offers versatile function modes such as trapping, sorting, and assembling of nanoparticles. It is believed that this approach holds the potential to be a valuable tool in fields such as synthetic biology, optofluidics, nanophotonics, and colloidal science.

Synergy of Nanoparticles Photovoltaic Trapping and Manipulation from Suspension Layer on Ferroelectric Crystal Surface

Synergy of Nanoparticles Photovoltaic Trapping and Manipulation from Suspension Layer on Ferroelectric Crystal Surface

Enhanced trapping properties induced by strong LSPR-exciton coupling in plasmonic tweezers.

Plasmonic tweezers break the diffraction limit and enable trap the deep-subwavelength particles. However, the innate scattering properties and the photothermal effect of metal nanoparticles pose challenges to their effective trapping and the non-damaging trapping of biomolecules. In this study, we investigate the enhanced trapping properties induced by strong coupling between localized surface plasmon resonances (LSPR) and excitons in plasmonic tweezers. The LSPR-exciton strong coupling exhibits an anticrossing behavior in dispersion curves with a markable Rabi splitting of 196 meV. Plasmonic trapping forces on excitons experience a significant increase within this strong coupling system due to higher longitudinal enhancement of electric field enhancement, which enables efficient particle trapping using lower laser power and minimizes ohmic heat generation. Moreover, leveraging strong coupling effects allows the successful trapping of a 50 nm Au particle coated with J-aggregates, overcoming previous limitations associated with scattering characteristics and smaller size that hindered effective metal nanoparticle manipulation. These findings open up new possibilities for the nondestructive trapping of biomolecules and metal nanoparticles across various applications.

Resonant optical trapping of Janus nanoparticles in plasmonic nanoaperture

Controlled trapping of light-absorbing nanoparticles with low-power optical tweezers is crucial for remote manipulation of small objects. This study takes advantage of the synergetic effects of tightly confined local fields of plasmonic nanoaperture, self-induced back-action (SIBA) of nanoparticles, and resonant optical trapping method to demonstrate enhanced manipulation of Janus nanoparticles in metallic nanohole aperture. We theoretically demonstrate that displacement of Au-coated Janus nanoparticles toward plasmonic nanoaperture and proper orientation of the metal coating give rise to enhanced near-field intensity and pronounced optical force. We also explore the effect of resonant optical trapping by employing a dual-laser system, where an on-resonant green laser excites the metal-coated nanoparticle, whereas an off-resonant near-infrared laser plays trapping role. It is found that, at the optimum nanoparticle configuration, the resonant optical trapping technique can result in threefold enhancement of optical force, which is attributed to the excitation of surface plasmon resonance in Janus nanoparticles. The findings of this study might pave the way for low-power optical manipulation of light-absorbing nanoparticles with possible applications in nanorobotics and drug delivery.

CRISPR-powered optothermal nanotweezers: Diverse bio-nanoparticle manipulation and single nucleotide identification

Optothermal nanotweezers have emerged as an innovative optical manipulation technique in the past decade, which revolutionized classical optical manipulation by efficiently capturing a broader range of nanoparticles. However, the optothermal temperature field was merely employed for in-situ manipulation of nanoparticles, its potential for identifying bio-nanoparticles remains largely untapped. Hence, based on the synergistic effect of optothermal manipulation and CRIPSR-based bio-detection, we developed CRISPR-powered optothermal nanotweezers (CRONT). Specifically, by harnessing diffusiophoresis and thermo-osmotic flows near the substrate upon optothermal excitation, we successfully trapped and enriched DNA functionalized gold nanoparticles, CRISPR-associated proteins, as well as DNA strands. Remarkably, we built an optothermal scheme for enhancing CRISPR-based single-nucleotide polymorphism (SNP) detection at single molecule level, while also introducing a novel CRISPR methodology for observing nucleotide cleavage. Therefore, this innovative approach has endowed optical tweezers with DNA identification ability in aqueous solution which was unattainable before. With its high specificity and feasibility for in-situ bio-nanoparticle manipulation and identification, CRONT will become a universal tool in point-of-care diagnosis, biophotonics, and bio-nanotechnology.

Nanoparticle Deep-Subwavelength Dynamics Empowered by Optical Meron-Antimeron Topology.

Optical meron is a type of nonplanar topological texture mainly observed in surface plasmon polaritons and highly symmetric points of photonic crystals in the reciprocal space. Here, we report Poynting-vector merons formed at the real space of a photonic crystal for a Γ-point illumination. Optical merons can be utilized for subwavelength-resolution manipulation of nanoparticles, resembling a topological Hall effect on electrons via magnetic merons. In particular, staggered merons and antimerons impose strong radiation pressure on large gold nanoparticles (AuNPs), while focused hot spots in antimerons generate dominant optical gradient forces on small AuNPs. Synergistically, differently sized AuNPs in a still environment can be trapped or orbit in opposite directions, mimicking a coupled galaxy system. They can also be separated with a 10 nm precision when applying a flow velocity of >1 mm/s. Our study unravels a novel way to exploit topological textures for optical manipulation with deep-subwavelength precision and switchable topology in a lossless environment.

On‐Demand Subwavelength‐Scale Light Sculpting Using Nanometric Holograms

AbstractSpatially or temporally structured light has attracted considerable attention for its intriguing beam characteristics, which have found extensive applications in classical and quantum optics. Extending structured light from macroscale and microscale to nanometricscale brings more prospects both for fundamental and applied science. However, sculpting light at the subwavelength scale remains a challenge since its transverse structure is fragile in the nanometric scale. Here a novelholography for arbitrary light sculpting at the subwavelength scale is demonstrated. A wave phenomenon of diffractive focusing from an amplitude‐only nanometric (50‐nm‐thick) film is introduced, and use of the induced high‐spatial‐frequency waves as carriers to encode information of an object is considered. Using this technique, nanometric holograms are designed and fabricated for generating the well‐defined eigen modes including the zero‐order Bessel beam, vortex beam, vector beam, Airy beam, as well as an arbitrary light pattern, with feature sizes on the deep‐subwavelength scale. The broadband performance of the hologram is examined, and a white‐light nondiffracting beam at the deep‐subwavelength scale is realized. This demonstration paves a way toward on‐demand light sculpting at the nanometric scale, which may find applications such as optical super‐resolution imaging, nanoparticle manipulation, and precise measurements.

Physical aspects of magnetic nanoparticle manipulation in environmental and biomedical applications

Microfluidic manipulation of magnetic nanoparticles (MNPs) is a smart tool for various environmental and biomedical applications. Unfortunately, these techniques have a strong limitation related to the low efficiency of magnetic manipulation of MNPs due to their Brownian motion. However, molecules adsorbed on the surface of MNPs can cause their weak (primary) aggregation. Once the magnetic field is applied, the magnetic force exerted on the primary aggregates will be strongly amplified allowing for significant improvement of the remote control over the MNPs by the magnetic fields. In this paper, we check this concept on three different physicochemical systems covering different application: (i) methylene blue cationic dye adsorbed on citrate coated MNPs for water purification; (ii) curcumin bound to the β-cyclodextrin modified MNPs for magnetic drug delivery; (iii) antigens bound to MNPs decorated with antibodies for model immunoassays. We find striking similarities of the magnetic-field induced behaviours of these different systems, with the dipolar coupling parameter, the supersaturation, the Mason number and the Peclet number being the main governing parameters. We also mention the possibility of using this concept for enhancement of the convective drug transport through the blocked blood vessels.

1 nm‐Resolution Sorting of Sub‐10 nm Nanoparticles Using a Dielectric Metasurface with Toroidal Responses

Sorting nanoparticles is of paramount importance in numerous physical, chemical, and biomedical applications. Current technologies for sorting dielectric nanoparticles have a common size limit and resolution approximately of 20 and 10 nm, respectively. It remains a grand challenge to push the limit. Herein, the new physics that deploys toroidal and multipole responses in a dielectric metasurface to exert strong and distinguishable optical forces on sub‐10 nm nanoparticles is unravelled. The electric toroidal dipole, electric dipole, and quadrupole emerge with distinct light and force patterns, which can be leveraged to promise unprecedented high‐precision manipulations, such as sorting sub‐10 nm polystyrene nanoparticles at 1 nm resolution, sorting 20 nm proteins/exsomes at 3 nm resolution, conveying, and concentrating 100 nm gold nanoparticles. Remarkably, the design can also be employed to screen out medium‐sized nanoparticles from a mixture of nanoparticles with over three sizes. This optofluidic manipulation platform opens the new way to explore intriguing optical modes for the powerful manipulation of nanoparticles with nanometer precisions and low laser powers.