Evaluation of a Trapping Potential Measurement Technique for Optical Tweezers Using Simulations and Experiments

2009 ◽  
Author(s):  
Arvind Balijepalli ◽  
Thomas W. LeBrun ◽  
Jason J. Gorman ◽  
Satyandra K. Gupta
Keyword(s):  
Optical Tweezers ◽  
Measurement Method ◽  
Force Measurement ◽  
Optical Trap ◽  
Two Dimensions ◽  
Trapping Potential ◽  
Potential Measurement ◽  
Trapping Force ◽  
Dynamics Simulations ◽  
Trapping Forces

A technique to measure the trapping force in an optical tweezers, without making any prior assumptions about the trap shape, has been extended to two-dimensions. The response of a trapped micro or nanoparticle to a step input is measured and then used to calculate the trapping force experienced by the particle as a function of its position in the trap. Langevin dynamics simulations have been implemented to evaluate the performance of this measurement method in two-dimensions and to evaluate whether the particle’s motion away from the measurement plane due to diffusion gives rise to an error in the trapping force measurement. Preliminary experimental results are also presented to demonstrate this method in the laboratory. This force measurement method provides insight into the trapping behavior of micro and nanoparticles in an optical trap beyond the region, close to the trap center, where the trapping force is assumed to vary linearly with the particle’s displacement. The measured trapping forces, from simulations and laboratory experiments, are then integrated to recover the shape of the optical trapping potential.

ANALYSIS OF TRANSVERSE AND LONGITUDINAL OPTICAL TRAP STIFFNESS AND ITS APPLICATION IN A NOVEL MEASUREMENT METHOD OF MICRO-PARTICLE REFRACTIVE INDEX

2010 ◽  
Vol 24 (23) ◽  
pp. 2431-2443 ◽  
Author(s):  
JIXIANG LI ◽  
XIAOLIN ZHANG ◽  
YOULI YU ◽  
WENJING LI ◽  
PENG LIU
Keyword(s):  
Refractive Index ◽  
Optical Tweezers ◽  
Measurement Method ◽  
Environmental Science ◽  
Medical Science ◽  
Optical Trap ◽  
Longitudinal Optical ◽  
Mineral Science ◽  
Micro Particles ◽  
Important Relationship

Based on the model of the single TEM00 Gaussian beam optical tweezers, the transverse and longitudinal optical trapping forces of micro-particles are calculated by ray-optics theory. The similarities and differences of the longitudinal optical trap shapes, which are computed by two different methods, are analyzed. We studied the relation between the optical trap stiffness and the particle parameters which include the size and refractive index (RI), and found that the ratio of the transverse and longitudinal stiffness is a constant when the refractive indices of the particles are the same. Through the analysis, the results show that there is an important relationship between the optical stiffness and the product of particle RI and radius. With this relationship, we can obtain the particle RI by measuring the optical stiffness and the particle radius. This novel micro-particle RI measurement method is of great usefulness in atmospheric environmental science, polymer chemistry science, identification of mineral science and bio-medical science.

scholarly journals Experimental investigation on optical vortex tweezers for microbubble trapping

Open Physics ◽  
2018 ◽  
Vol 16 (1) ◽  
pp. 383-386 ◽  
Author(s):  
Xiaoming Zhou ◽  
Ziyang Chen ◽  
Zetian Liu ◽  
Jixiong Pu
Keyword(s):  
Optical Tweezers ◽  
Laser Power ◽  
Topological Charge ◽  
Force Measurement ◽  
Numerical Aperture ◽  
Optical Vortex ◽  
Gradient Force ◽  
Vortex Beam ◽  
Trapping Forces ◽  
Topological Charges

AbstractIn this paper, we investigated the microbubble trapping using optical vortex tweezers. It is shown that the microbubble can be trapped by the vortex optical tweezers, in which the trapping light beam is of vortex beam. We studied a relationship between the transverse capture gradient force and the topological charges of the illuminating vortex beam. For objective lenses with numerical aperture of 1.25 (100×), the force measurement was performed by the power spectral density (PSD) roll-off method. It was shown that transverse trapping forces of vortex optical tweezers increase with the increment of the laser power for fixed topological charge. Whereas, the increase in the topological charges of vortex beam for the same laser power results in the decrease of the transverse trapping forces. The experimental results demonstrated that the laser mode (topological charge) has significant influence on the lateral trapping force.

Nanometric plasmonic optical trapping on gold nanostructures

2019 ◽  
Vol 86 (3) ◽  
pp. 30501
Author(s):  
Domna G. Kotsifaki ◽  
Mersini Makropoulou ◽  
Alexander A. Searfetinides
Keyword(s):  
Optical Tweezers ◽  
Single Molecule ◽  
Optical Trapping ◽  
Numerical Aperture ◽  
Resonance Wavelength ◽  
Objective Lens ◽  
Plasmonic Nanostructures ◽  
Theoretical Support ◽  
Trapping Force ◽  
Trapping Forces

The precise noninvasive optical manipulation of nanometer-sized particles by evanescent fields, instead of the conventional optical tweezers, has recently awaken an increasing interest, opening a way for investigating phenomena relevant to both fundamental and applied science. In this work, the optical trapping force exerted on trapped dielectric nanoparticle was theoretically investigated as a function on the trapping beam wavelength and as a function of several plasmonic nanostructures schemes based on numerical simulation. The maximum optical trapping forces are obtained at the resonance wavelength for each plasmonic nanostructure geometry. Prominent tunabilities, such as radius and separation of gold nanoparticles as well as the numerical aperture of objective lens were examined. This work will provide theoretical support for developing new types of plasmonic sensing substrates for exciting biomedical applications such as single-molecule fluorescence.

Tuning the Electric Field Response of MOFs by Rotatable Dipolar Linkers

2019 ◽  
Author(s):  
Johannes P. Dürholt ◽  
Babak Farhadi Jahromi ◽  
Rochus Schmid
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Structural Changes ◽  
Dielectric Behavior ◽  
Two Dimensions ◽  
Dielectric Constants ◽  
Electric Response ◽  
Dipole Strength ◽  
Metal Organic ◽  
Dynamics Simulations

Recently the possibility of using electric fields as a further stimulus to trigger structural changes in metal-organic frameworks (MOFs) has been investigated. In general, rotatable groups or other types of mechanical motion can be driven by electric fields. In this study we demonstrate how the electric response of MOFs can be tuned by adding rotatable dipolar linkers, generating a material that exhibits paralectric behavior in two dimensions and dielectric behavior in one dimension. The suitability of four different methods to compute the relative permittivity κ by means of molecular dynamics simulations was validated. The dependency of the permittivity on temperature T and dipole strength μ was determined. It was found that the herein investigated systems exhibit a high degree of tunability and substantially larger dielectric constants as expected for MOFs in general. The temperature dependency of κ obeys the Curie-Weiss law. In addition, the influence of dipolar linkers on the electric field induced breathing behavior was investigated. With increasing dipole moment, lower field strength are required to trigger the contraction. These investigations set the stage for an application of such systems as dielectric sensors, order-disorder ferroelectrics or any scenario where movable dipolar fragments respond to external electric fields.

Insights into the roles of charged residues in substrate binding and mode of action of mannuronan C-5 epimerase AlgE4

Glycobiology ◽  
2021 ◽  
Author(s):  
Margrethe Gaardløs ◽  
Sergey A Samsonov ◽  
Marit Sletmoen ◽  
Maya Hjørnevik ◽  
Gerd Inger Sætrom ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Conformational Changes ◽  
Molecular Mechanisms ◽  
Hydrophobic Interactions ◽  
Substrate Binding ◽  
Interdisciplinary Approach ◽  
Product Formation ◽  
Titration Calorimetry ◽  
Binding Groove ◽  
Dynamics Simulations

Abstract Mannuronan C-5 epimerases catalyse the epimerization of monomer residues in the polysaccharide alginate, changing the physical properties of the biopolymer. The enzymes are utilized to tailor alginate to numerous biological functions by alginate-producing organisms. The underlying molecular mechanisms that control the processive movement of the epimerase along the substrate chain is still elusive. To study this, we have used an interdisciplinary approach combining molecular dynamics simulations with experimental methods from mutant studies of AlgE4, where initial epimerase activity and product formation were addressed with NMR spectroscopy, and characteristics of enzyme-substrate interactions were obtained with isothermal titration calorimetry and optical tweezers. Positive charges lining the substrate-binding groove of AlgE4 appear to control the initial binding of poly-mannuronate, and binding also seems to be mediated by both electrostatic and hydrophobic interactions. After the catalytic reaction, negatively charged enzyme residues might facilitate dissociation of alginate from the positive residues, working like electrostatic switches, allowing the substrate to translocate in the binding groove. Molecular simulations show translocation increments of two monosaccharide units before the next productive binding event resulting in MG-block formation, with the epimerase moving with its N-terminus towards the reducing end of the alginate chain. Our results indicate that the charge pair R343-D345 might be directly involved in conformational changes of a loop that can be important for binding and dissociation. The computational and experimental approaches used in this study complement each other, allowing for a better understanding of individual residues’ roles in binding and movement along the alginate chains.

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.

Ultrasonic measurement of clamping force for injection molding machine

2019 ◽  
Vol 39 (4) ◽  
pp. 388-396 ◽  
Author(s):  
Peng Zhao ◽  
Yao Zhao ◽  
Jianfeng Zhang ◽  
Junye Huang ◽  
Neng Xia ◽  
...  
Keyword(s):  
Injection Molding ◽  
Measurement Method ◽  
Large Scale ◽  
Force Measurement ◽  
Low Cost ◽  
Ultrasonic Method ◽  
Injection Molding Process ◽  
Propagation Time ◽  
Clamping Force ◽  
Molding Process

AbstractAn online and feasible clamping force measurement method is important in the injection molding process and equipment. Based on the sono-elasticity theory, anin situclamping force measurement method using ultrasonic technology is proposed in this paper. A mathematical model is established to describe the relationship between the ultrasonic propagation time, mold thickness, and clamping force. A series of experiments are performed to verify the proposed method. Experimental findings show that the measurement results of the proposed method agree well with those of the magnetic enclosed-type clamping force tester method, with difference squares less than 2 (MPa)2and errors bars less than 0.7 MPa. The ultrasonic method can be applied in molds of different thickness, injection molding machines of different clamping scales, and large-scale injection cycles. The proposed method offers advantages of being highly accurate, highly stable, simple, feasible, non-destructive, and low-cost, providing significant application prospects in the injection molding industry.

scholarly journals Hard discs under steady shear: comparison of Brownian dynamics simulations and mode coupling theory

2009 ◽  
Vol 367 (1909) ◽  
pp. 5033-5050 ◽  
Author(s):  
Oliver Henrich ◽  
Fabian Weysser ◽  
Michael E. Cates ◽  
Matthias Fuchs
Keyword(s):  
Brownian Dynamics ◽  
Mode Coupling ◽  
Transition Density ◽  
Two Dimensions ◽  
Coupling Theory ◽  
Mode Coupling Theory ◽  
Stationary Structure ◽  
Homogeneous Shear Flow ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

Brownian dynamics simulations of bidisperse hard discs moving in two dimensions in a given steady and homogeneous shear flow are presented close to and above the glass transition density. The stationary structure functions and stresses of shear-melted glass are compared quantitatively to parameter-free numerical calculations of monodisperse hard discs using mode coupling theory within the integration through transients framework. Theory qualitatively explains the properties of the yielding glass but quantitatively overestimates the shear-driven stresses and structural anisotropies.

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.

Crystal to Glass Transition and Melting in Two Dimensions

1993 ◽  
Vol 321 ◽  
Author(s):  
M. Li ◽  
W. L. Johnson ◽  
W. A. Goddard
Keyword(s):  
Glass Transition ◽  
Intermediate Phase ◽  
Orientational Order ◽  
Finite Size ◽  
Two Dimensions ◽  
Size Difference ◽  
Two Dimensional ◽  
Atomic Size ◽  
Bond Orientational Order ◽  
Dynamics Simulations

ABSTRACTThermodynamic properties, structures, defects and their configurations of a two-dimensional Lennard-Jones (LJ) system are investigated close to crystal to glass transition (CGT) via molecular dynamics simulations. The CGT is achieved by saturating the LJ binary arrays below glass transition temperature with one type of the atoms which has different atomic size from that of the host atoms. It was found that for a given atomic size difference larger than a critical value, the CGT proceeds with increasing solute concentrations in three stages, each of which is characterized by distinct behaviors of translational and bond-orientational order correlation functions. An intermediate phase which has a quasi-long range orientational order but short range translational order has been found to exist prior to the formation of the amorphous phase. The destabilization of crystallinity is observed to be directly related to defects. We examine these results in the context of two dimensional (2D) melting theory. Finite size effects on these results, in particular on the intermediate phase formation, are discussed.

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