Particle Manipulation Research Articles

Scattering characteristics of dual counter-propagation high-order circularly symmetric Bessel beam by a multilayer chiral sphere

The interaction between dual counter-propagating high-order circularly symmetric Bessel beams (CSBBs) and multi-layered chiral particles is investigated. Within the framework of generalized Lorenz-Mie theory (GLMT), the distribution characteristics of the superposition of two beams are studied based on the vector superposition theorem. The near-field, internal field, and far-field radar cross section (RCS) of the dual-layered chiral sphere illuminated by dual CSBBs are obtained according to the boundary conditions. By comparing the results of RCS with those from the references for two cases: first, when CSBBs degenerate into plane waves incident on multi-layered chiral sphere, and second, when Bessel beams illuminate isotropic multi-layer sphere degenerated by chiral multi-layered sphere, the effectiveness of the principle and program exhibited here is confirmed. The impact of various parameters on the distribution of the superposed field, the near-field, internal field, and far-field RCS of the particles are analyzed in detail, such as the order, half-cone angle, incidence angle, and polarization angle. The research results in this paper provide theoretical assistance for understanding the interaction between dual CSBBs and non-uniform chiral multi-layered particles and have important value in realizing optical manipulation of complex chiral layered particles.

Relativistic effects on entangled single-electron traps

The manipulation of individual charged particles has been deeply explored in physics’s theoretical and experimental domains during the past decades. It is the pillar of several existing devices used for metrology and sensing and is a promising platform for realizing future technologies, such as quantum computers. It is also known that in the relativistic regime, interactions between charged particles become affected by post-Coulombian corrections, with the dominant couplings encoded in the . The Darwin term has been extensively studied in atomic physics, where the interaction range is confined to the sub-angstrom scale. Still, there is a lack of understanding about whether (and when) Darwin’s contributions are relevant at larger scales. In this paper, we explore the effects of these corrections in a system of two harmonically trapped electrons, where we look into the behavior of quantum entanglement present in the static and dynamical regimes. We explore the parameter space of the developed model and seek frequencies, distances, and squeezing parameters for which relativistic effects become relevant for the generation of entanglement. Published by the American Physical Society 2024

Machine learning assisted sorting of active microswimmers.

Active matter systems, being in a non-equilibrium state, exhibit complex behaviors, such as self-organization, giving rise to emergent phenomena. There are many examples of active particles with biological origins, including bacteria and spermatozoa, or with artificial origins, such as self-propelled swimmers and Janus particles. The ability to manipulate active particles is vital for their effective application, e.g., separating motile spermatozoa from nonmotile and dead ones, to increase fertilization chance. In this study, we proposed a mechanism-an apparatus-to sort and demix active particles based on their motility values (Péclet number). Initially, using Brownian simulations, we demonstrated the feasibility of sorting self-propelled particles. Following this, we employed machine learning methods, supplemented with data from comprehensive simulations that we conducted for this study, to model the complex behavior of active particles. This enabled us to sort them based on their Péclet number. Finally, we evaluated the performance of the developed models and showed their effectiveness in demixing and sorting the active particles. Our findings can find applications in various fields, including physics, biology, and biomedical science, where the sorting and manipulation of active particles play a pivotal role.

Thermo-optical tweezers based on photothermal waveguides

Field-controlled micromanipulation represents a pivotal technique for handling microparticles, yet conventional methods often risk physical damage to targets. Here, we discovered a completely new mechanism for true noncontact manipulation through photothermal effects, called thermal-optical tweezers. We employ a laser self-assembly photothermal waveguide (PTW) for dynamic microparticle manipulation. This waveguide demonstrates superior photothermal conversion and precision control, generating a nonisothermal temperature field. The interaction of thermal convection and thermophoresis within this field creates a microfluidic potential well, enabling noncontact and nondestructive particle manipulation. By varying the path of PTWs in lithography and manipulating laser loading modes, diverse manipulation strategies, such as Z-shaped migration, periodic oscillation, and directional transport, are achievable. Our innovative noninvasive micromanipulation technology minimizes not only physical damage to target objects but also enables precise and diverse manipulation of micro entities, opening up new avenues for the photothermal control of cells and biomolecules.

Particle manipulation based on curved, slanted-finger interdigital transducer

Abstract In this paper, an acoustic particle manipulation device is proposed to realize multi-function particle operation in a droplet. A curved slanted-finger interdigital transducer is designed to excite surface acoustic wave (SAW) in different resonance frequency. Diversity acoustic pressure field can be formed by turning the excitation frequency of the transducer. Moreover, through switching the excitation combination of the interdigital transducers, different acoustic field distributions can be aotained and diversity acoustic stream can be formed in the droplet. A finite element model is setup to study the acoustic field distribution and acoustic stream. Simulation results show that when a single frequency SAW is excited, acoustic streaming can be formed in the fluid and the particles can be rotated in the droplet. By switching the excitation frequency of the interdigital transducer, the direction of acoustic stream can be changed. In addition, the interdigital transducer can simultaneously excite multiple surface acoustic waves of different frequencies, which can manipulate the particles move in different tragectory. The study provides an effectively device to multi-function particle manipulation.

Characteristic analysis of the vortex excited using the photoacoustic transducer with a spiral light absorption surface

Abstract It is proved that the vortex acoustic field can be excited with laser by designing the photoacoustic transducer with a spiral light absorption surface. The generated acoustic field has a spiral phase wavefront, and the pressure on the central axis along its propagation direction is zero. The orbital angular momentum that can be used for positioning and manipulation of particles is formed by the vortex. The characteristics of the generated acoustic vortex at different frequency and detection position are analyzed for 1-5 topological charge. And the influence of the geometric configurations such as the width and size of logarithmic spiral slot are also studied for the achieving the desired vortex field with focused intensity.

Detachable holographic acoustofluidic chip for striped acoustic field modulation and particle manipulation

The development of detachable acoustofluidic devices is of great significance for disposable and cost-effective biological and chemical analysis. In this work, a highly integrated holographic acoustofluidic device based on acoustic holography and microfluidic chips was proposed to realize the modulation of striped acoustic field in microchannels. In the device, the chip is disposable and the transducer is reused. The acoustic hologram was fabricated by injection molding for efficient manufacturing and low cost. In addition, a multiphysics simulation model for holographic acoustofluidic chip was established to analyze the effect of acoustic field modulation and particle manipulation. Results showed that the acoustic pressure inside the microchannel of the device exhibits a clear striped distribution, and a linear arrangement of particles parallel and inclined to the extension direction of the channel wall can be achieved within 2 s. The distance between the arrangement lines in the target region was controlled at around 60 μm. The investigation of thermal effect validates the biocompatibility. The designed holographic acoustofluidic device presents a promising option for the manipulation, arrangement, and sorting of cells and other particles in microchannels.

Phase-modulated pulsing coherent acoustic tweezers for dynamic adjustable spaced particle patterning

Abstract Acoustic tweezer technique with non-contact micro-object manipulation capability has been widely utilized for particle patterning in the fields of cell arraying, target drug delivery, and functional composite fabrication. However, the manipulation resolution of acoustic tweezer device is decided by the configuration of interdigital transducers (IDTs), which is half the wavelength of surface acoustic waves (SAWs). This limitation severely reduces the manipulation versatility of acoustic tweezer devices. To address this limitation, we propose a novel approach that employs phase-modulated pulsing coherent SAWs. This method can halve the patterning spacing and allows for customization of the spacing based on specific manipulation demands. Our proposed technique increases the flexibility and manipulation resolution of acoustic tweezer device, and thus can be widely applied to reconfigurable assembly and precise manipulation of particles and cells.

Application of Resonant Plasmonic Bowtie Nanoantennas for Optically‐Assisted Diffusiophoretic Trapping of Extracellular Vesicles and Nanoparticles

AbstractPlasmonic antennas leveraging localized surface plasmon resonances (LSPR) hold a significant premise for efficiently trapping nanoscale particles at low power levels. However, their effectiveness is hindered by photothermal effects that arise with metallic nanoparticles, leading to decreased stability of trapped particles. To address this limitation, a hybrid approach that combines depletion attraction and photothermal effects inherent in plasmonic structures is proposed, capitalizing on thermally induced concentration gradients. Through the thermophoretic depletion of polyethylene glycol (PEG) molecules around plasmonic hotspots, sharp concentration gradients are created, enabling precise localization of nanoscopic particles through a synergistic effect with diffusiophoretic forces. Our experiments successfully demonstrate the ability to trap and dynamically manipulate small extracellular vesicles and 100 nm polystyrene beads, showcasing the platform's potential for assembly at the nanoscale. Remarkably, this method maintains stable trapping performance even at a laser power of . The demonstration of stable trapping of small extracellular vesicles showcases the compatibility of this platform with bio species. This study introduces a promising avenue for the precise and efficient manipulation of nanoscale particles, with wide‐ranging implications in nanotechnology, biophysics, and nanomedicine. This research opens new opportunities for advancing nanoscale particle studies and applications, ushering in a new era of nanoscale manipulation techniques.

Inertial migration of rigid particles in shear-thinning fluids under asymmetric wall slip conditions

The determination of flow-induced equilibrium positions in pressure-driven flows in microchannels is of great practical importance in particle manipulation. In the computational analysis presented in this paper, the inertial ordering of neutrally buoyant rigid spheres in shear-thinning fluid flow through a hydrophobic microchannel is investigated. The combined effect of the viscosity index n of a power-law fluid and fluid slippage at the wall on the lateral focusing of microspheres is examined in detail. Using the finite element method, the Eulerian flow field between partially slipping parallel walls is simulated, and the Lagrangian movement of particles is continuously tracked. The Navier slip model is used to ensure a finite fluid velocity at the wall, and it is tuned by modifying the slip-length. It is observed that inertial particles concentrate at a standard equilibrium position of 0.6 times the channel half-width H, irrespective of fluid slip due to the symmetry of the flow field. However, this equilibrium position shifts closer to the walls as the viscosity index increases; for instance, when n = 0.5, particles stabilize at 0.75H. As a consequence of asymmetry in hydrodynamic behavior due to different fluid slippages at the upper and lower walls, the particle migration path is altered. In a channel with a no-slip upper wall and a partially slipping lower wall (β/H = 0.4), particles settle closer to the lower wall at 0.8H. Most importantly, the lateral movement of a particle released at a given vertical position can be altered by tailoring the wall hydrophobicity and viscosity index, thus enabling multiple equilibrium locations to be achieved.

Recent Advances in Dielectrophoretic Manipulation and Separation of Microparticles and Biological Cells.

Dielectrophoresis (DEP) is an advanced microfluidic manipulation technique that is based on the interaction of polarized particles with the spatial gradient of a non-uniform electric field to achieve non-contact and highly selective manipulation of particles. In recent years, DEP has made remarkable progress in the field of microfluidics, and it has gradually transitioned from laboratory-scale research to high-throughput manipulation in practical applications. This paper reviews the recent advances in dielectric manipulation and separation of microparticles and biological cells and discusses in detail the design of chip structures for the two main methods, direct current dielectrophoresis (DC-DEP) and alternating current dielectrophoresis (AC-DEP). The working principles, technical implementation details, and other improved designs of electrode-based and insulator-based chips are summarized. Functional customization of DEP systems with specific capabilities, including separation, capture, purification, aggregation, and assembly of particles and cells, is then performed. The aim of this paper is to provide new ideas for the design of novel DEP micro/nano platforms with the desired high throughput for further development in practical applications.

Pearcey Talbot-like plasmon: a plasmonic bottle array generation scheme.

In this Letter, a surface wave, the Pearcey Talbot-like plasmon, which has the properties of self-imaging and multiple autofocusing, is presented as a novel, to the best of our knowledge, plasmonic bottle array generation scheme. With originality, the overall structure and the partial intensity of the plasmonic bottle array can be adjusted through the initial input, and modifying the Pearcey function enables the plasmonic bottle array to exhibit self-bending characteristics, which makes particle capture and manipulation easier and more flexible. A scheme to generate the plasmon is proposed, and we prove it by the finite-difference time-domain numerical simulations.

Particle manipulation based on the controllable light field of graphene nano-butterfly structures

In this Letter, we have proposed a nano-optical convey belt consisting of three sets of graphene nano-butterfly structures (GNBS) with different lengths arranged in a periodic pattern to trap, transport, and sort particles depending on controlling the Fermi level of graphene. The graphene nano-butterfly structure, based on a couple of trapezoids, can form a potential well to capture particles by localized surface plasmon resonance under the excitation of an incident laser. There are three adjustable geometric parameters containing width (W1, W2) and length (L) that make the GNBS have a high degree of design flexibility. Graphene can support surface plasmons in the mid-infrared region, and at the same time, it possesses a more flexible tuning mechanism compared to metals. When the incident light power is 1 mW/μm2 and the resonance wavelength is 10.6 μm, the depth of the potential well is greater than 10KbT for 50 nm particles. Moreover, the sorting of particles with different diameters has also been validated under appropriate power and switching time. Based on the capabilities of capture and sorting verified by numerical analysis, our design offers a new scheme for on-chip optofluidic applications.

A numerical study of Elasto-inertial particle-focusing in straight and serpentine microchannels

Microfluidic devices have gained popularity in recent years due to their low cost and simplicity. Cell focusing linked with cell counting and cell separation used in clinical tests and point-of-care devices stands towards the top of every list of microfluidic applications. To focus and manipulate particles in a Newtonian medium, inertial microfluidics has been widely used. There is a requirement to replace a significantly more efficient approach given various particle-focusing positions near the channel walls recorded by inertial microfluidics. Here, the synergetic effect of elastic and inertial forces in relatively low-concentration viscoelastic fluids was investigated numerically. Utilizing particle-focusing behavior in straight and serpentine channels with different corner angles, by applying the numerical results obtained using the developed direct numerical simulation method (DNS) for elastic and inertial forces, we created a microchannel with a remarkable performance. As the flow regime transitions to elasto-inertial, where inertial forces are comparable to elastic forces in a straight microchannel, particles tend to concentrate at the channel centerline. As the flow rate increases, however, particle defocusing develops, and shear gradient lift forces ultimately overcome elastic forces in the channel's central region. Given that fluid flows at a higher velocity in the serpentine channel with a corner angle of 75° than in other channels, the Dean drag force induced by secondary flow serves to reduce particle defocusing rate at a given flow rate, making this channel a desirable platform for Elasto-inertial microfluidics. Particle focusing in a vertical direction was noticed as a benefit of elasto-inertial microfluidics, regardless of the geometry or flow rate of the particles passing through the channel. Finally, the impact of particle diameter on focusing behavior was studied. As particle diameter decreases, focusing width decreases and the focusing band shifts to the left side of the cross-section. We expect that the numerical evaluation of using viscoelastic medium in complex geometries can contribute to accelerate the three dimensional particle-focusing mechanism and enhance the efficiency of microdevices for cell and particle manipulation.

Dual-Function Multichannel Acoustofluidic Particle Manipulation Enabled by a PMUT Array

Dual-Function Multichannel Acoustofluidic Particle Manipulation Enabled by a PMUT Array

Quantitative determination of fractional topological charge based on the rotational Doppler effect

The utilization of fractional-order vortex beams extends the diversity of optical field manipulation, permits for more flexible control over beam propagation, and provides novel applications in optical communications, edge enhancement imaging, and particle manipulation. However, compared with the integer-order vortex beams, the topological charge measurement techniques for fractional-order vortex beams are not well developed, impeding the further exploration of its applications. In this paper, the frequency signal of rotational Doppler effect and corresponding broadening behavior under the fractional-order vortex beam illumination were analyzed. When the fractional topological charge approaches a half integer, the broadening is minimized. Leveraging this relationship, we designed a phase-compensated scheme coupled with signal-to-noise ratio detection to realize the real-time fractional topological charge measurement. The single pixel photodetector was used and eliminated the need for two-dimensional image acquisition and analysis, ensuring efficient acquisition and quantitative analysis. Both theoretical and experimental results confirm the feasibility of this method, thereby advancing the comprehension of the optical Doppler effect and potentially paving the way for future investigations into fractional vortex beams.

Numerical and experimental demonstrations of optical trapping and manipulation of a selective red blood cell using a photonic hook based on broken symmetry tapered fiber probe

Optical tweezers and trapping technologies have a crucial impact on scientific research by precisely manipulating mesoscale objects at wavelength scales. The development of simple fiber-based optical tweezers foreseeing sorting and manipulation of a single cell has been firstly encouraged by biomedical requirements. The ability to manipulate mesoscale objects with high flexibility and precision is essential for a wide class of different fields. The ability to precisely arrange cells into desired structures is important for numerous biomedical and physical applications. This study experimentally reports for the first time a simple and low-cost strategy to produce an optical fiber-based photonic hook for achieving new unprecedented functionalities to selective particle manipulation in a lab-on-tip platform. We show perspectives opened by combining the fields of structured light in the form of the photonic hook and optical manipulation method. This enables new applications for optical trapping setups based on structured fields in the form of the photonic hook produced by an optical fiber tip with broken symmetry, where it becomes possible to manipulate and sort cells selectively.

Liquid Springs for High‐Speed Contamination‐Free Manipulation of Droplets and Solid Particles

AbstractAccurate and flexible control of droplets is essential in many industrial applications, such as water harvesting, chemical assays, and biological detection. Magnetic force‐based methods have been broadly exploited to fulfill the goals due to the advantage of non‐contact, easy control, and long‐range navigation. Nevertheless, it still suffers from some challenges, such as sample fouling, and the paradox between the droplet efficient motion and the large volume. Here a ferrofluid‐based liquid spring to achieve contamination‐free and fast droplet transportation on non‐wetting solid surfaces is proposed. The liquid spring is based on the actuation of a ferrofluid droplet in an external uniform magnetic field. The actuation enables the liquid spring to propel tiny objects, including the non‐magnetic miscible droplets and water‐repellent solid particles, with adjustable motion velocity. Furthermore, the magnetic force, applied on the ferrofluid via an additional permanent magnet, makes it possible to navigate the liquid spring in a programmable way. With the aid of the liquid spring, the single or multiple droplets/solid particles advancing, on‐demand droplets coalescence, and out‐of‐plane droplet motion are achievable.

Opto-Thermal-Tension Mediated Precision Large-Scale Particle Manipulation and Flexible Patterning.

Large-scale particle manipulation with single-particle precision and further flexible patterning into functional structures is of huge potentials in many fields including bio-optoelectronic sensing, colloidal lithography, and wearable devices. However, it is very challenging for the precision manipulation and flexible patterning of particles on complicated curved and functional substrates. In this work, opto-thermal-tension (OTT) mediated precision large-scale particle manipulation and flexible patterning based on soap film are reported. Flexible manipulation and subsequent patterning of particles with single-particle resolution is realized by optothermal regulated surface tension on soap films. Reconfigurable patterning of particle structures with different shapes as well as large-scale ordered structures (up to 2000 particles) with particle sizes spanning two orders of magnitude (0.5-20µm) is realized using this OTT mediation method. Importantly, due to the high flexibility of soap films, the patterned large-scale particle structures can be non-destructively transferred to curved and rough substrates, including rough iron pipe surface, leaf and skin surface. This OTT mediated method provides a new method for precision large-scale particle manipulation and flexible patterning with high versatility on complicated functional substrates, with great potentials for optoelectronic and biophotonic sensing and wearable device design on different curved and rough functional substrates.

Layer-by-Layer Nanoparticle Assembly for Biomedicine: Mechanisms, Technologies, and Advancement via Acoustofluidics.

The deposition of thin films plays a crucial role in surface engineering, tailoring structural modifications, and functionalization across diverse applications. Layer-by-layer self-assembly, a prominent thin-film deposition method, has witnessed substantial growth since its mid-20th-century inception, driven by the discovery of eligible materials and innovative assembly technologies. Of these materials, micro- and nanoscopic substrates have received far less interest than their macroscopic counterparts; however, this is changing. The catalogue of eligible materials, including nanoparticles, quantum dots, polymers, proteins, cells and liposomes, along with some well-established layer-by-layer technologies, have combined to unlock impactful applications in biomedicine, as well as other areas like food fortification, and water remediation. To access these fields, several well-established technologies have been used, including tangential flow filtration, fluidized bed, atomization, electrophoretic assembly, and dielectrophoresis. Despite the invention of these technologies, the field of particle layer-by-layer still requires further technological development to achieve a high-yield, automatable, and industrially ready process, a requirement for the diverse, reactionary field of biomedicine and high-throughput pharmaceutical industry. This review provides a background on layer-by-layer, focusing on how its constituent building blocks and bonding mechanisms enable unmatched versatility. The discussion then extends to established and recent technologies employed for coating micro- and nanoscopic matter, evaluating their drawbacks and advantages, and highlighting promising areas in microfluidic approaches, where one distinctly auspicious technology emerges, acoustofluidics. The review also explores the potential and demonstrated application of acoustofluidics in layer-by-layer technology, as well as analyzing existing acoustofluidic technologies beyond LbL coating in areas such as cell trapping, cell sorting, and multidimensional particle manipulation. Finally, the review concludes with future perspectives on layer-by-layer nanoparticle coating and the potential impact of integrating acoustofluidic methods.