Manipulation Of Nanoparticles Research Articles

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.

Nanoparticle manipulation based on chiral plasmon effects.

Chiral plasmonic structures have garnered increasing attention owing to their distinctive chiroptical response. Localized surface plasmon resonance can significantly enhance the circular dichroism and local electromagnetic field of chiral plasmonic structures, resulting in enhanced electromagnetic forces acting on surrounding nanoparticles. Moreover, the circular dichroism response of chiral structures provides an effective means for macroscopic adjustment of microscopic electromagnetic fields. However, chiral plasmon effects are naturally related to angular momentum, and particle control studies of chirality usually focus on angular momentum. This paper proposes a particle manipulation method utilizing chiral light-matter interactions. Through optimization of the optical response of the chiral structure, the direction of electromagnetic forces exerted on surrounding polystyrene particles reverses upon a change in the incident light's handedness. According to this characteristic, the movement direction control of polystyrene particles with a diameter of 100 nm was achieved. By altering the handedness of a single circularly polarized light, more than 94% high-precision particle manipulation was achieved, reducing the complexity of particle manipulation. This microfluidic method has significant implications for advancing microfluidic research and chiral applications.

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.

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.

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

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.

Advanced active polymer probe for near-field optics.

We report on a novel, to the best of our knowledge, active probe for scanning near-field optical microscopy (SNOM). A fluorescent nanosphere, acting as the secondary source, is grafted in an electrostatic manner at the apex of a polymer tip integrated into the extremity of an optical fiber. Thanks to the high photostability and sensitivity of the secondary source, the near-field interaction with a gold nanocube is investigated. It is shown that the spatial resolution is well defined by the size of the fluorescent nanosphere. The polarization-dependent near-field images, which are consistent with the simulation, are ascribed to the local excitation rate enhancement. Meanwhile, measurement of the distance-dependent fluorescence lifetime of the nanosphere provides strong evidence that the local density of states is modified so that extra information on nano-emitters can be extracted during near-field scanning. This advanced active probe can thus potentially broaden the range of applications to include nanoscale thermal imaging, biochemical sensors, and the manipulation of nanoparticles.

Directionally duplexed all-dielectric metalens for multifunctional structured light generation.

Directionally duplexed metalenses manipulated by the geometric phase of a silicon nano-bar are theoretically designed to generate multifunctional structured light. It is numerically demonstrated that incident light with different linear and circular polarization states, along forward and backward propagation directions, can be differentially converted into multiple focusing structured beams of arbitrary topological charges, either of vector light with azimuthally variant polarizations or of vortex light with helical phases. Due to the all-silicon and nonresonant metastructural design, the resultant high working efficiencies of our proposed metalens are promising for applications such as optical communication, nanoparticle manipulation, and other direction-duplexed multifunctional optical meta-devices.

Analytical model of optical force on supercavitating plasmonic nanoparticles.

Optical manipulation of nanoparticles (NPs) in liquid has garnered increasing interest for various applications, ranging from biological systems to nanofabrication. A plane wave as an optical source has recently been shown to be capable of pushing or pulling an NP when the NP is encapsulated by a nanobubble (NB) in water. However, the lack of an accurate model to describe the optical force on NP-in-NB systems hinders a comprehensive understanding of NP motion mechanisms. In this study, we present an analytical model using vector spherical harmonics to accurately capture the optical force and the resultant trajectory of an NP in an NB. We test the developed model using a solid Au NP as an example. By visualizing the vector field line of the optical force, we reveal the possible moving paths of the NP in the NB. This study can provide valuable insights for designing experiments to manipulate supercaviting NPs using plane waves.

Dynamic Trapping and Manipulation of Self-Assembled Ag Nanoplates as Efficient Plasmonic Tweezers.

Plasmonic tweezers based on periodic nanostructures have been used to manipulate particles through multiple and uniform local surface plasmon (LSP) fields. However, the coverage area of periodic nanostructures is limited, which restricts the range of trapping and manipulation. In this paper, we present a novel approach to achieve large-scale manipulation and trapping of microspheres by uniformly coupled LSP fields on a short-range disordered self-assembled Ag nanoplates (DSNP) film. The DSNP film is prepared by simple and low-cost methods─chemical growth and self-assembly technique, which overcome the challenges of preparing periodic nanostructures with a large coverage area. The uniform and coupled plasmon fields generated by this film provide enhanced electrodynamic interactions with particles, enabling the non-invasive and repeatable trapping of particles in solution. Utilizing sensitive LSPRs, dynamic manipulating particles was achieved by controlling the laser position. This large-scale platform of stable manipulation enabled by the DSNP film opens up new possibilities for the trapping and manipulation of nanoparticles in a variety of applications.

Investigations on the optical forces from three mainstream optical resonances in all-dielectric nanostructure arrays.

Light can exert radiation pressure on any object it encounters, and the resulting optical force can be used to manipulate particles at the micro- or nanoscale. In this work, we present a detailed comparison through numerical simulations of the optical forces that can be exerted on polystyrene spheres of the same diameter. The spheres are placed within the confined fields of three optical resonances supported by all-dielectric nanostructure arrays, including toroidal dipole (TD), anapoles, and quasi-bound states in continuum (quasi-BIC) resonances. By elaborately designing the geometry of a slotted-disk array, three different resonances can be supported, which are verified by the multipole decomposition analysis of the scattering power spectrum. Our numerical results show that the quasi-BIC resonance can produce a larger optical gradient force, which is about three orders of magnitude higher than those generated from the other two resonances. The large contrast in the optical forces generated with these resonances is attributed to a higher electromagnetic field enhancement provided by the quasi-BIC. These results suggest that the quasi-BIC resonance is preferred when one employs all-dielectric nanostructure arrays for the trapping and manipulation of nanoparticles by optical forces. It is important to use low-power lasers to achieve efficient trapping and avoid any harmful heating effects.

Trends and challenges in microfluidic methods for protein manipulation-A review.

Proteins are important molecules involved in an immensely large number of biological processes. Being capable of manipulating proteins is critical for developing reliable and affordable techniques to analyze and/or detect them. Such techniques would enable the production of therapeutic agents for the treatment of diseases or other biotechnological applications (e.g., bioreactors or biocatalysis). Microfluidic technology represents a potential solution to protein manipulation challenges because of the diverse phenomena that can be exploited to achieve micro- and nanoparticle manipulation. In this review, we discuss recent contributions made in the field of protein manipulation in microfluidic systems using different physicochemical principles and techniques, some of which are miniaturized versions of already established macro-scale techniques.

Scaling Perspective on Dynamics of Nanoparticles in Polymers: Length- and Time-Scale Dependent Nanoparticle–Polymer Coupling

The motion of nanoparticles in a polymer matrix is dictated by the intricate coupling of the nanoparticles and surrounding polymers. Various length- and time-scale dependent features of nanoparticle–polymer coupling in a polymer matrix have been delineated in the past decade by combining scaling theory and molecular simulations. Representative scenarios of nanoparticle dynamics in polymers, which embody the roles of polymer matrix topology, the polymers grafted to nanoparticle surface, the anisotropic shape of nanoparticles, and an external driving force, are reviewed. The systems examined demonstrate both the richness of the physics in the nanoparticle–polymer coupling and the capability of the scaling-level description in providing unique insights into the size- and time-dependence of nanoparticle mobility. Following a review of recent work, more scenarios of nanoparticles in polymer matrices, which reflect new pieces of physics in the nanoparticle–polymer coupling, are discussed. Together with the advances in the chemical synthesis of nanoparticles and polymers as well as in the techniques of tracking nanoparticle motion and measuring nanoparticle diffusivity, the microscopic picture of nanoparticle–polymer coupling revealed theoretically and computationally is anticipated to aid in the manipulation of nanoparticles in complex polymeric environments and thus benefit many technological applications.

Fully Microfabricated Surface Acoustic Wave Tweezer for Collection of Submicron Particles and Human Blood Cells.

Precise manipulation of (sub)micron particles is key for the preparation, enrichment, and quality control in many biomedical applications. Surface acoustic waves (SAW) hold tremendous promise for manipulation of (bio)particles at the micron to nanoscale ranges. In commonly used SAW tweezers, particle manipulation relies on the direct acoustic radiation effect whose superior performance fades rapidly when progressing from micron to nanoscale particles due to the increasing dominance of a second order mechanism, termed acoustic streaming. Through reproducible and high-precision realization of stiff microchannels to reliably actuate the microchannel cross-section, here we introduce an approach that allows the otherwise competing acoustic streaming to complement the acoustic radiation effect. The synergetic effect of both mechanisms markedly enhances the manipulation of nanoparticles, down to 200 nm particles, even at relatively large wavelength (300 μm). Besides spherical particles ranging from 0.1 to 3 μm, we show collections of cells mixed with different sizes and shapes inherently existing in blood including erythrocytes, leukocytes, and thrombocytes.