Manipulation Of Micro Research Articles

Acoustofluidics-Assisted Fluorescence-SERS Bimodal Biosensors.

Acoustofluidics, the fusion of acoustics and microfluidic techniques, has recently seen increased research attention across multiple disciplines due in part to its capabilities in contactless, biocompatible, and precise manipulation of micro-/nano-objects. Herein, a bimodal signal amplification platform which relies on acoustofluidics-induced enrichment of nanoparticles is introduced. The dual-function biosensor can perform sensitive immunofluorescent or surface-enhanced Raman spectroscopy (SERS) detection. The platform functions by using surface acoustic waves to concentrate nanoparticles at either the center or perimeter of a glass capillary; the concentration location is adjusted simply by varying the input frequency. The immunofluorescence assay is achieved by concentrating fluorescent analytes and functionalized nanoparticles at the center of the microchannel, thereby improving the visibility of the fluorescent output. By modifying the inner wall of the glass capillary with plasmonic Ag nanoparticle-deposited ZnO nanorod arrays and focusing analytes toward the perimeter of the microchannel, SERS sensing using the same device setup is achieved. Nanosized exosomes are used as a proof-of-concept to validate the performance of the acoustofluidic bimodal biosensor. With its sample-enrichment functionality, bimodal sensing, short processing time, and minute sample consumption, the acoustofluidic chip holds great potential for the development of lab-on-a-chip based analysis systems in many real-world applications.

Optical Manipulation of Micro- and Nanoobjects Based on Structured Mesoscale Particles: a Brief Review

Spatial resolution of conventional optics, which is necessary for nondestructive trapping of microobjects, is limited by diffraction to a value equal to half of the radiation wavelength. Despite this limitation, use of optical methods is one of the main directions in biological and biomedical researches because only these methods have a minimal impact on living organisms. The rapid advance in this area is largely owing to the development of new optical technologies and the considerable advance in mesoscale photonics, which has allowed researchers to develop techniques for controlling structured beams for optical traps. In this work, we consider some recent trends in the field of optical manipulation based on mesoscale dielectric particles.

The Entangled Structure of Elastic Dipoles and a Twist Disclination Line in a Nematic Phase

The studies concerning 1/2 disclinations started with a focus on the fact that the interactions between the disclination and the microparticle accompanied by topological defects can be explained in a similar manner with electrostatic interactions. Therefore, the interactions in the elastic field have been revealed but the details concerning how the microparticles are entangled with the disclination lines have not been studied. However, because the applications of the entangled structures and the disclination itself are growing in periodic assembling and manipulation of micro- and nanoparticles, further detailed study is necessary. Thus, the detailed entangled structure of the twist disclination line and elastic dipoles is discussed in this work and we were able to conclude that the disclination line through the middle of the bead in the entangled structure acts as a −1/2 disclination line and the hedgehog point defect around the bead disappears because of the change of the director field configuration. In addition, zigzag entangled structures are created in order to lower the elastic energy due to the bend deformation. Based on these results, we will be able to discuss the entangled structure of ±1/2 disclination lines and elastic dipoles.

Influence of components of optical momentum and spin of evanescent waves on micro- and nanoobjects (Review)

Background: Mechanical properties of light are widely used in applied areas, such as optical trapping and manipulation, sorting, deformation of biological cells and molecules. In general, the evanescent field may exhibit three components of optical momentum and spin angular momentum (spin), which manifest themselves in the occurrence of corresponding components of optical force and torque. Such extraordinary properties of evanescent waves open up new possibilities for manipulating of micro- and nanoobjects, in comparing with classical optical tweezers and manipulators, which can be used for solving the applied problems, in particular, of biomedicine. Objectives: Aim of this work is to analyze and summarize recent studies regarding to the mechanical influence of evanescent field on micro- and nanoobjects, in particular, related to the influence of transverse components of optical momentum and spin. Materials and methods: Method of momenta allows one to distinguish in an evanescent field the action of optical forces and torques, associated with the components of optical momentum and angular momentum of different nature and action direction, depending on the polarization of the incident wave. Experimental methods of particle manipulation in the near field allow visualizing such an influence, which makes it possible for solving the applied problems. Results: Recent studies demonstrate the action on nano- and microobjects of such "extraordinary" optical momentum and spin components, as transverse spin momentum, transverse spin, transverse imaginary optical momentum component, and vertical spin. Using, in particular, the latter, to solve the applied problems of biomedicine is proposed, such as transporting of therapeutic agents to pathological areas or restoring vascular patency and tissue blood supply. Conclusions: Obtained results of theoretical and experimental investigation of the mechanical action of the optical momentum and spin components of evanescent field allow us to extend the approaches of optical manipulation of micro- and nanoobjects, with the possibility of applications, in particular, for the problems of biomedicine.

Recent advances in manipulation of micro- and nano-objects with magnetic fields at small scales

Magnetic manipulation is very promising for the motion control of micro- and nano-objects, which has wide applications in the mixing, trapping, colloidal assembly and object transport, and the recent progress in these areas is reviewed in this work.

Manipulation of micro- and nanoparticles in viscoelastic fluid flows within microfluid systems.

Manipulation of micro- and nanoparticles in complex biofluids is highly demanded in most biological and biomedical applications. A significant number of microfluidic platforms have been developed for inexpensive, rapid, accurate, and efficient particle manipulation. Due to the enormous potential of viscoelastic fluids (VEFs) for particle manipulation, various emerging microfluidic-based VEFs techniques have been presented over the last decade. This review provides an intuitive understanding of VEF physics for particle separation in different microchannel geometries. Besides, active and passive VEF methods are critically reviewed, highlighting the potential and practical challenges of each technique for particle/cell focusing, sorting, and separation. The outcome of this study could enable recognizing deliverable VEF technology with the promising prospect in the manipulation of submicron biological samples (e.g., exosomes, DNA, and proteins).

Optical-force-directed single-particle-based track etching in polystyrene films

The establishment of optical trapping theory by A Ashkin almost half a century ago led to the trapping and manipulation of micro-/nano-objects and atoms by laser beams, which is now applied in many fields. However, in a complex system where multi-physical effects interact synergistically, light–matter interaction becomes dynamic and complicated and is still poorly understood. Here, by utilising plasmonic heating, nanolithography of polystyrene (PS) films and nanomanipulation of gold nanoparticles are realised. We find that laser power and PS film thickness as well as particle shape strongly affect the etching behaviour of the PS films, which is a synergistic effect of photothermal ablation and optical forces. Theoretical calculations and simulations rationalise the proposed mechanism, which is also verified by experimental observation. This understanding not only sheds light on how the synergistic effect of photo-ablation and optical forces acts on the particles and polymer films, but also provides a guideline for light-directed single-particle-based nanolithography and nanomanipulation.

Measuring local properties inside a cell-mimicking structure using rotating optical tweezers.

Exploring the rheological properties of intracellular materials is essential for understanding cellular and subcellular processes. Optical traps have been widely used for physical manipulation of micro and nano objects within fluids enabling studies of biological systems. However, experiments remain challenging as it is unclear how the probe particle's mobility is influenced by the nearby membranes and organelles. We use liposomes (unilamellar lipid vesicles) as a simple biomimetic model of living cells, together with a trapped particle rotated by optical tweezers to study mechanical and rheological properties inside a liposome both theoretically and experimentally. Here, we demonstrate that this system has the capacity to predict the hydrodynamic interaction between three-dimensional spatial membranes and internal probe particles within submicron distances, and it has the potential to aid in the design of high resolution optical micro/nanorheology techniques to be used inside living cells.

An Interdisciplinary Approach to the Nanomanipulation of SiO2 Nanoparticles: Design, Fabrication and Feasibility

Although some recent developments in nanotechnology made the prospects of a direct mechanical manipulation of micro- or nano-objects quite realistic, there are still several concerns and difficulties that affect such an endeavor. This is probably due to the large base of knowledge that is necessary to approach the problem of handling a nano-object by means of a nano- or micro-device. Therefore, any progress in this field is possible only by means of an integrated and interdisciplinary approach, which takes into account different aspects of the phenomenon. During the actual pioneering phase, there is a certain convenience in handling nano-objects that: (a) have peculiar known characteristics; (b) are easily recognizable, and (c) are interesting to the scientific community. This paper presents the interdisciplinary activities that were necessary to set up an experiment where specifically synthesized SiO2 particles came in contact with the tips of specifically-designed and -fabricated nanomanipulators. SiO2 mesoporous nanoparticles (KCC-1), having a peculiar dendritic structure, have been selected as a suitable nano-object because of the possibility to easily modulate their morphology. The expected contact force has been also calculated by means of Finite Element Analysis (FEA) electro-mechanical simulations.

Thermophoretic Manipulation of Micro- and Nanoparticle Flow through a Sudden Contraction in a Microchannel with Near-Infrared Laser Irradiation

Micro- and nanochannels are promising for state-of-the-art sensing technologies in biomedical devices, but the accurate and selective control of nanomaterials near the sensing elements is a challenge. This paper rises to the challenge by introducing an unconventional manipulation technique, combining laser-induced thermophoresis with a sudden narrowing of the channel. The strength of thermophoresis, compared to other transport mechanisms, lies in its selectivity: Targets can be guided to the sudden contraction, while unwanted particles are repelled. Also, the nearby flow field leads to dynamical concentration of target materials.

Hypersonic‐Induced 3D Hydrodynamic Tweezers for Versatile Manipulations of Micro/Nanoscale Objects

AbstractDeveloping microrobots for precisely manipulating micro/nanoscale objects has triggered tremendous research interest for various applications in biology, chemistry, physics, and engineering. Here, a novel hypersonic‐induced hydrodynamic tweezers (HSHTs), which use gigahertz nano‐electromechanical resonator to create localized 3D vortex streaming array for the capture and manipulation of micro‐ and nanoparticles in three orientations: transportation in a plane and self‐rotation in place, are presented. 3D vortex streaming can effectively pick up particles from the flow, whereas the high‐speed rotating vortices are used to drive self‐rotation simultaneously. By tuning flow rate, the captured particles can be delivered, queued, and selectively sorted through the 3D HSHTs. Through numerical simulations and theoretical analysis, the generation of the 3D vortex and the mechanism of the particles manipulation by ultrahigh frequency acoustic wave are demonstrated. Benefitting from the advantages of the acoustic and hydrodynamic method, the developed HSHTs work in a precise, noninvasive, label‐free, and contact‐free manner, enabling wide applications in micro/nanoscale manipulations and biomedical research.

Micro-Dumbbells-A Versatile Tool for Optical Tweezers.

Manipulation of micro- and nano-sized objects with optical tweezers is a well-established, albeit still evolving technique. While many objects can be trapped directly with focused laser beam(s), for some applications indirect manipulation with tweezers-operated tools is preferred. We introduce a simple, versatile micro-tool operated with holographic optical tweezers. The 40 µm long dumbbell-shaped tool, fabricated with two-photon laser 3D photolithography has two beads for efficient optical trapping and a probing spike on one end. We demonstrate fluids viscosity measurements and vibration detection as examples of possible applications.

Plasmonic Manipulation of Targeted Metallic Particles by Polarization-Sensitive Metalens

As a tool in the manipulation of micro- and nano-objects, optical tweezers are found in applications in many areas. However, selective trapping still poses challenges. Recently, a meta-surface technique offers an approach to improve optical trapping and manipulation capabilities. Here, we demonstrate the selective trapping of metallic nanoparticles with tailored plasmonic fields using a polarization sensitive metalens. We show, both by theory and experiments, modulated trapping and antitrapping forces when beam polarizations are tuned. Combining the effects of two orthogonal circular polarizations, single target particles were stably trapped in the center, while all other particles were repelled. This particle isolation points toward targeted manipulations that may find applications in single-particle assistant molecular Raman detection and assembly of plasmonic structures.

Acoustic Manipulation of Bio-Particles at High Frequencies: An Analytical and Simulation Approach.

Manipulation of micro and nano particles in microfluidic devices with high resolution is a challenge especially in bioengineering applications where bio-particles (BPs) are separated or patterned. While acoustic forces have been used to control the position of BPs, its theoretical aspects need further investigation particularly for high-resolution manipulation where the wavelength and particle size are comparable. In this study, we used a finite element method (FEM) to amend analytical calculations of acoustic radiation force (ARF) arising from an imposed standing ultrasound field. First, an acoustic solid interaction (ASI) approach was implemented to calculate the ARF exerted on BPs and resultant deformation induced to them. The results were then used to derive a revised expression for the ARF beyond the small particle assumption. The expression was further assessed in numerical simulations of one- and multi-directional standing acoustic waves (SAWs). Furthermore, a particle tracing scheme was used to investigate the effect of actual ARF on separation and patterning applications under experimentally-relevant conditions. The results demonstrated a significant mismatch between the actual force and previous analytical predictions especially for high frequencies of manipulation. This deviation found to be not only because of the shifted ARF values but also due to the variation in force maps in multidirectional wave propagation. Findings of this work can tackle the simulation limitations for spatiotemporal control of BPs using a high resolution acoustic actuation.

Motion Manipulation of Micro- and Nanomotors.

Inspired by the self-migration of microorganisms in nature, artificial micro- and nanomotors can mimic this fantastic behavior by converting chemical fuel or external energy into mechanical motion. These self-propelled micro- and nanomotors, designed either by top-down or bottom-up approaches, are able to achieve different applications, such as environmental remediation, sensing, cargo/sperm transportation, drug delivery, and even precision micro-/nanosurgery. For these various applications, especially biomedical applications, regulating on-demand the motion of micro- and nanomotors is quite essential. However, it remains a continuing challenge to increase the controllability over motors themselves. Here, we will discuss the recent advancements regarding the motion manipulation of micro- and nanomotors by different approaches.

Micro- and nano-patterned conductive graphene-PEG hybrid scaffolds for cardiac tissue engineering.

A lack of electrical conductivity and structural organization in currently available biomaterial scaffolds limits their utility for generating physiologically representative models of functional cardiac tissue. Here we report on the development of scalable, graphene-functionalized topographies with anisotropic electrical conductivity for engineering the structural and functional phenotypes of macroscopic cardiac tissue constructs. Guided by anisotropic electroconductive and topographic cues, the tissue constructs displayed structural property enhancement in myofibrils and sarcomeres, and exhibited significant increases in the expression of cell-cell coupling and calcium handling proteins, as well as in action potential duration and peak calcium release.

Polarization conversion when focusing cylindrically polarized vortex beams.

Currently, cylindrical beams with radial or azimuthal polarization are being used successfully for the optical manipulation of micro- and nano-particles as well as in microscopy, lithography, nonlinear optics, materials processing, and telecommunication applications. The creation of these laser beams is carried out using segmented polarizing plates, subwavelength gratings, interference, or light modulators. Here, we demonstrate the conversion of cylindrically polarized laser beams from a radial to an azimuthal polarization, or vice versa, by introducing a higher-order vortex phase singularity. To simultaneously generate several vortex phase singularities of different orders, we utilized a multi-order diffractive optical element. Both the theoretical and the experimental results regarding the radiation transmitted through the diffractive optical element show that increasing the order of the phase singularity leads to more efficient conversation of the polarization from radial to azimuthal. This demonstrates a close connection between the polarization and phase states of electromagnetic beams, which has important implications in many optical experiments.

Optical forces in nanorod metamaterial.

Optomechanical manipulation of micro and nano-scale objects with laser beams finds use in a large span of multidisciplinary applications. Auxiliary nanostructuring could substantially improve performances of classical optical tweezers by means of spatial localization of objects and intensity required for trapping. Here we investigate a three-dimensional nanorod metamaterial platform, serving as an auxiliary tool for the optical manipulation, able to support and control near-field interactions and generate both steep and flat optical potential profiles. It was shown that the ‘topological transition’ from the elliptic to hyperbolic dispersion regime of the metamaterial, usually having a significant impact on various light-matter interaction processes, does not strongly affect the distribution of optical forces in the metamaterial. This effect is explained by the predominant near-fields contributions of the nanostructure to optomechanical interactions. Semi-analytical model, approximating the finite size nanoparticle by a point dipole and neglecting the mutual re-scattering between the particle and nanorod array, was found to be in a good agreement with full-wave numerical simulation. In-plane (perpendicular to the rods) trapping regime, saddle equilibrium points and optical puling forces (directed along the rods towards the light source), acting on a particle situated inside or at the nearby the metamaterial, were found.

LiNbO3: A photovoltaic substrate for massive parallel manipulation and patterning of nano-objects

The application of evanescent photovoltaic (PV) fields, generated by visible illumination of Fe:LiNbO3 substrates, for parallel massive trapping and manipulation of micro- and nano-objects is critically reviewed. The technique has been often referred to as photovoltaic or photorefractive tweezers. The main advantage of the new method is that the involved electrophoretic and/or dielectrophoretic forces do not require any electrodes and large scale manipulation of nano-objects can be easily achieved using the patterning capabilities of light. The paper describes the experimental techniques for particle trapping and the main reported experimental results obtained with a variety of micro- and nano-particles (dielectric and conductive) and different illumination configurations (single beam, holographic geometry, and spatial light modulator projection). The report also pays attention to the physical basis of the method, namely, the coupling of the evanescent photorefractive fields to the dielectric response of the nano-particles. The role of a number of physical parameters such as the contrast and spatial periodicities of the illumination pattern or the particle deposition method is discussed. Moreover, the main properties of the obtained particle patterns in relation to potential applications are summarized, and first demonstrations reviewed. Finally, the PV method is discussed in comparison to other patterning strategies, such as those based on the pyroelectric response and the electric fields associated to domain poling of ferroelectric materials.

Automated Robotic Manipulation of Individual Colloidal Particles Using Vision-Based Control

Automated manipulation of micro- and nanosized objects using robotic setups constitutes a major challenge due to the force-scaling laws and the limited control possibilities on that scale. This paper presents a new developed approach for automated manipulation of individual colloidal particles using a dedicated dual-probe setup inside a scanning electron microscope. Based on tailored probe geometries, the setup allows for reliable pick-up and release sequences of individual particles. Applying image processing of the visual feedback provided by the microscope enables for direct and fast control of the complex manipulation routines and thus allows for fully automated alignment sequences. Experimental results reveal a high repeatability of the process with hitherto unrivaled precision. The advantages and limits of this technique are highlighted with respect to further application scenarios.