scholarly journals Microrheology With an Anisotropic Optical Trap

2021 ◽  
Vol 9 ◽  
Author(s):  
Andrew B. Matheson ◽  
Tania Mendonca ◽  
Graham M. Gibson ◽  
Paul A. Dalgarno ◽  
Amanda J. Wright ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Optical Trap ◽  
Threshold Level ◽  
Optical Traps ◽  
Elliptical Cross ◽  
Maximum Variance ◽  
The Difference ◽  
Axes Of Symmetry ◽  
Spurious Results ◽  
Arbitrary Axis

Microrheology with optical tweezers (MOT) measurements are usually performed using optical traps that are close to isotropic across the plane being imaged, but little is known about what happens when this is not the case. In this work, we investigate the effect of anisotropic optical traps on microrheology measurements. This is an interesting problem from a fundamental physics perspective, but it also has practical ramifications because in 3D all optical traps are anisotropic due to the difference in the intensity distribution of the trapping laser along axes parallel and perpendicular to the direction of beam propagation. We find that attempting viscosity measurements with highly anisotropic optical traps will return spurious results, unless the axis with maximum variance in bead position is identified. However, for anisotropic traps with two axes of symmetry such as traps with an elliptical cross section, the analytical approach introduced in this work allows us to explore a wider range of time scales than those accessible with symmetric traps. We have also identified a threshold level of anisotropy in optical trap strength of ~30%, below which conventional methods using a single arbitrary axis can still be used to extract valuable microrheological results. We envisage that the outcomes of this study will have important practical ramifications on how all MOT measurements should be conducted and analyzed in future applications.

scholarly journals Reliable and mobile all-fiber modular optical tweezers

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Chaoyang Ti ◽  
Yao Shen ◽  
Minh-Tri Ho Thanh ◽  
Qi Wen ◽  
Yuxiang Liu
Keyword(s):  
Optical Tweezers ◽  
Optical Fibers ◽  
Point Of Care ◽  
Optical Trap ◽  
Optical Traps ◽  
Modular System ◽  
Breast Epithelial Cell ◽  
Epithelial Cell Line ◽  
Position Detection ◽  
Breast Epithelial Cell Line

AbstractMiniaturization and integration of optical tweezers are attractive. Optical fiber-based trapping systems allow optical traps to be realized in miniature systems, but the optical traps in these systems lack reliability or mobility. Here, we present the all-fiber modular optical tweezers (AFMOTs), in which an optical trap can be reliably created and freely moved on a sample substrate. Two inclined optical fibers are permanently fixed to a common board, rendering a modular system where fiber alignments are maintained over months. The freely movable optical trap allows particles to be trapped in their native locations. As a demonstration, we applied AFMOTs to trap and deform freely floating individual cells. By the cell mechanical responses, we differentiated the nontumorigenic breast epithelial cell line (MCF10A) from its cancerous PTEN mutants (MCF10 PTEN-/-). To further expand the functionalities, three modalities of AFMOTs are demonstrated by changing the types of fibers for both the optical trap creation and particle position detection. As a miniature and modular system that creates a reliable and mobile optical trap, AFMOTs can find potential applications ranging from point-of-care diagnostics to education, as well as helping transition the optical trapping technology from the research lab to the field.

Enhancing Range of Transport in Optical Tweezers Assisted Microfluidic Chambers Using Automated Stage Motion

2013 ◽  
Author(s):  
Sagar Chowdhury ◽  
Petr Švec ◽  
Atul Thakur ◽  
Chenlu Wang ◽  
Wolfgang Losert ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
High Speed ◽  
Optical Trap ◽  
Heuristic Method ◽  
Optical Traps ◽  
Greedy Heuristic ◽  
Long Distance ◽  
Microfluidic Chamber ◽  
Planning Approach ◽  
Cell Ensemble

In this paper, we present a planning approach for automated high-speed transport of cells over large distances inside an Optical Tweezers (OT) assisted microfluidic chamber. The transport is performed in three steps that combine the optical trap and motorized stage motions. This includes optical trapping and transporting the cells to form a desired cell-ensemble that is suitable for a long distance transport, automatically moving the motorized stage to transport the cell-ensemble over a large distance while avoiding static obstacles, and distributing the cells from the ensemble to the desired locations using OT. The speeds of optical traps and the motorized stage are determined by modeling the motion of the particle under the influence of optical trap. The desired cell-ensemble is automatically determined based on the geometry of the microfluidic chamber. We have developed a greedy heuristic method for optimal selection of the initial and the final location of the cell-ensemble to minimize the overall transport time while satisfying the constraints of the OT workspace. We have discussed the computational complexity of the developed method and compared it with exhaustive combinatorial search. The approach is particularly useful in applications where cells are needed to be rapidly distributed inside a microfluidic chamber. We show the capability of our planning approach using physical experiments.

scholarly journals Generation of Hybrid Optical Trap Array by Holographic Optical Tweezers

2021 ◽  
Vol 9 ◽  
Author(s):  
Xing Li ◽  
Yuan Zhou ◽  
Yanan Cai ◽  
Yanan Zhang ◽  
Shaohui Yan ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Optical Trap ◽  
Optical Traps ◽  
Axial Position ◽  
Spatial Light Modulators ◽  
Light Modulators ◽  
Multiple Particles ◽  
Holographic Optical Tweezers ◽  
Almost All ◽  
Gaussian Point

Enabled by multiple optical traps, holographic optical tweezers can manipulate multiple particles in parallel flexibly. Spatial light modulators are widely used in holographic optical tweezers, in which Gaussian point (GP) trap arrays or special mode optical trap arrays including optical vortex (OV) arrays, perfect vortex (PV) arrays, and Airy beam arrays, etc., can be generated by addressing various phase holograms. However, the optical traps in these arrays are almost all of the same type. Here, we propose a new method for generating a hybrid optical trap array (HOTA), where optical traps such as GPs, OVs, PVs, and Airy beams in the focal plane are combined arbitrarily. Also, the axial position and peak intensity of each them can be adjusted independently. The energy efficiency of this method is theoretically studied, while different micro-manipulations on multiple particles have been realized with the support of HOTA experimentally. The proposed method expands holographic optical tweezers’ capabilities and provides a new possibility of multi-functional optical micro-manipulation.

scholarly journals Positioning Accuracy in Holographic Optical Traps

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 559
Author(s):  
Frederic Català-Castro ◽  
Estela Martín-Badosa
Keyword(s):  
Optical Tweezers ◽  
Dynamic Control ◽  
Optical Trap ◽  
Optical Traps ◽  
Spatial Light Modulators ◽  
Positioning Accuracy ◽  
Light Modulators ◽  
Holographic Optical Tweezers ◽  
The One ◽  
Optically Trapped

Spatial light modulators (SLMs) have been widely used to achieve dynamic control of optical traps. Often, holographic optical tweezers have been presumed to provide nanometer or sub-nanometer positioning accuracy. It is known that some features concerning the digitalized structure of SLMs cause a loss in steering efficiency of the optical trap, but their effect on trap positioning accuracy has been scarcely analyzed. On the one hand, the SLM look-up-table, which we found to depend on laser power, produces positioning deviations when the trap is moved at the micron scale. On the other hand, phase quantization, which makes linear phase gratings become phase staircase profiles, leads to unexpected local errors in the steering angle. We have tracked optically trapped microspheres with sub-nanometer accuracy to study the effects on trap positioning, which can be as high as 2 nm in certain cases. We have also implemented a correction strategy that enabled the reduction of errors down to 0.3 nm.

scholarly journals Enhanced Signal-to-Noise and Fast Calibration of Optical Tweezers Using Single Trapping Events

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 570
Author(s):  
Alexander B. Stilgoe ◽  
Declan J. Armstrong ◽  
Halina Rubinsztein-Dunlop
Keyword(s):  
Brownian Motion ◽  
Optical Tweezers ◽  
Optical Trap ◽  
Force Transducer ◽  
Signal To Noise ◽  
Likelihood Estimator ◽  
Micro Fluidics ◽  
Large Numbers ◽  
Force Reconstruction ◽  
Micron Particle

The trap stiffness us the key property in using optical tweezers as a force transducer. Force reconstruction via maximum-likelihood-estimator analysis (FORMA) determines the optical trap stiffness based on estimation of the particle velocity from statistical trajectories. Using a modification of this technique, we determine the trap stiffness for a two micron particle within 2 ms to a precision of ∼10% using camera measurements at 10 kfps with the contribution of pixel noise to the signal being larger the level Brownian motion. This is done by observing a particle fall into an optical trap once at a high stiffness. This type of calibration is attractive, as it avoids the use of a nanopositioning stage, which makes it ideal for systems of large numbers of particles, e.g., micro-fluidics or active matter systems.

ORIENTATING MANIPULATION OF CYLINDRICAL PARTICLES WITH OPTICAL TWEEZERS

2008 ◽  
Vol 17 (04) ◽  
pp. 387-394 ◽  
Author(s):  
XIUDONG SUN ◽  
XUECONG LI ◽  
JIANLONG ZHANG
Keyword(s):  
Escherichia Coli ◽  
Carbon Nanotubes ◽  
Laser Beam ◽  
Optical Tweezers ◽  
Optical Trap ◽  
Polarization Direction ◽  
Beam Shape ◽  
E Coli ◽  
Potential Applications ◽  
Cylindrical Particles

Orientating manipulations of cylindrical particles were performed by optical tweezers. Vertical and horizontal manipulations of Escherichia coli (E. coli) were carried out by changing the trapping depth and the focused laser beam shape. It was found that carbon nanotubes bundles (CNTBs) could be rotated in the linear polarized optical trap until it orientated its long axis along the linear polarization direction of the laser beam. However, E.coli could not be orientated in this way. Corresponding mechanisms were discussed based on the anisomeric electric characters of CNTBs. These orientation technologies of cylindrical objects with optical trap have potential applications in assembling nano-electric devices.

A semi-hybrid model for malaria with limited superinfection

1998 ◽  
Vol 30 (04) ◽  
pp. 1027-1057 ◽  
Author(s):  
Philippe Picard
Keyword(s):  
Stochastic Model ◽  
Population Size ◽  
Hybrid Model ◽  
Human Population ◽  
Threshold Level ◽  
The Other ◽  
The Difference ◽  
The One

Modelling malaria with consistency necessitates the introduction of at least two families of interconnected processes. Even in a Markovian context the simplest fully stochastic model is intractable and is usually transformed into a hybrid model, by supposing that these two families are stochastically independent and linked only through two deterministic connections. A model closer to the fully stochastic model is presented here, where one of the two families is subordinated to the other and just a unique deterministic connection is required. For this model a threshold theorem can be proved but the threshold level is not the one obtained in a hybrid model. The difference disappears only when the human population size approaches infinity.

Numerical Analysis of Branch Mechanical Response to Loading

2019 ◽  
Vol 45 (4) ◽  
Author(s):  
Barbora Vojáčková ◽  
Jan Tippner ◽  
Petr Horáček ◽  
Luděk Praus ◽  
Václav Sebera ◽  
...  
Keyword(s):  
Finite Element ◽  
Cross Sections ◽  
Mechanical Response ◽  
Mechanical Analysis ◽  
Beam Deflection ◽  
Design System ◽  
Elliptical Cross ◽  
Static Mechanical ◽  
The Difference ◽  
Tree Uprooting

Failure of a tree can be caused by a stem breakage, tree uprooting, or branch failure. While the pulling test is used for assessing the first two cases, there is no device-supported method to assess branch failure. A combination of the optical technique, pulling test, and deflection curve analysis could provide a device-supported tool for this kind of assessment. The aim of the work was to perform a structural analysis of branch response to static mechanical loading. The analyses were carried out by finite element simulations in ANSYS using beam tapered elements of elliptical cross-sections. The numerical analyses were verified by the pulling test combined with a sophisticated optical assessment of deflection evaluation. The Probabilistic Design System was used to find the parameters that influence branch mechanical response to loading considering the use of cantilever beam deflection for stability analysis. The difference in the branch’s deflection between the simulation and the experiment is 0.5% to 26%. The high variability may be explained by the variable modulus of the elasticity of branches. The finite element (FE) sensitivity analysis showed a higher significance of geometry parameters (diameter, length, tapering, elliptical cross-section) than material properties (elastic moduli). The anchorage rotation was found to be significant, implying that this parameter may affect the outcome in mechanical analysis of branch behavior. The branch anchorage can influence the deflection of the whole branch, which should be considered in stability assessment.

Optimal trap velocity in a dynamic holographic optical trap using a nematic liquid crystal spatial light modulator

2022 ◽  
Author(s):  
Karuna Sindhu Malik ◽  
Bosanta Ranjan Boruah
Keyword(s):  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Spatial Light Modulator ◽  
Optical Trap ◽  
Optical Element ◽  
Optical Traps ◽  
Light Modulator ◽  
Step Size ◽  
Microscopic Object ◽  
Optimal Velocity

Abstract A dynamic holographic optical trap uses a dynamic diffractive optical element such as a liquid crystal spatial light modulator to realize one or more optical traps with independent controls. Such holographic optical traps provide a number of flexibilities and conveniences useful in various applications. One key requirement for such a trap is the ability to move the trapped microscopic object from one point to the other with the optimal velocity. In this paper we develop a nematic liquid crystal spatial light modulator based holographic optical trap and experimentally investigate the optimal velocity feasible for trapped beads of different sizes, in such a trap. Our results show that the achievable velocity of the trapped bead is a function of size of the bead, step size, interval between two steps and power carried by the laser beam. We observe that the refresh rate of a nematic liquid crystal spatial light modulator is sufficient to achieve an optimal velocity approaching the theoretical limit in the respective holographic trap for beads with radius larger than the wavelength of light.

scholarly journals Bio-Molecular Applications of Recent Developments in Optical Tweezers

Biomolecules ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 23 ◽  
Author(s):  
Dhawal Choudhary ◽  
Alessandro Mossa ◽  
Milind Jadhav ◽  
Ciro Cecconi
Keyword(s):  
Photonic Crystal ◽  
Optical Tweezers ◽  
Single Molecule ◽  
Continuous Wave ◽  
Imaging Techniques ◽  
Resolving Power ◽  
Optical Traps ◽  
Laser Source ◽  
One Dimensional

In the past three decades, the ability to optically manipulate biomolecules has spurred a new era of medical and biophysical research. Optical tweezers (OT) have enabled experimenters to trap, sort, and probe cells, as well as discern the structural dynamics of proteins and nucleic acids at single molecule level. The steady improvement in OT’s resolving power has progressively pushed the envelope of their applications; there are, however, some inherent limitations that are prompting researchers to look for alternatives to the conventional techniques. To begin with, OT are restricted by their one-dimensional approach, which makes it difficult to conjure an exhaustive three-dimensional picture of biological systems. The high-intensity trapping laser can damage biological samples, a fact that restricts the feasibility of in vivo applications. Finally, direct manipulation of biological matter at nanometer scale remains a significant challenge for conventional OT. A significant amount of literature has been dedicated in the last 10 years to address the aforementioned shortcomings. Innovations in laser technology and advances in various other spheres of applied physics have been capitalized upon to evolve the next generation OT systems. In this review, we elucidate a few of these developments, with particular focus on their biological applications. The manipulation of nanoscopic objects has been achieved by means of plasmonic optical tweezers (POT), which utilize localized surface plasmons to generate optical traps with enhanced trapping potential, and photonic crystal optical tweezers (PhC OT), which attain the same goal by employing different photonic crystal geometries. Femtosecond optical tweezers (fs OT), constructed by replacing the continuous wave (cw) laser source with a femtosecond laser, promise to greatly reduce the damage to living samples. Finally, one way to transcend the one-dimensional nature of the data gained by OT is to couple them to the other large family of single molecule tools, i.e., fluorescence-based imaging techniques. We discuss the distinct advantages of the aforementioned techniques as well as the alternative experimental perspective they provide in comparison to conventional OT.

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