Measuring the interaction between a pair of emulsion droplets using dual-trap optical tweezers

Griffiths, Marjorie; Raudsepp, Allan; McGrath, Kathryn M.; Williams, Martin A. K.

doi:10.1039/c5ra25073k

Cited by 18 publications

(9 citation statements)

References 24 publications

(36 reference statements)

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“…Additionally, this poses a particular barrier for the use of microrobots in biological research, where studies are often carried out in particular fluids which are intended to mimic in vivo conditions. Some of these fluids, such as the tris-buffered saline used for DNA stretching [117], have relatively high salt concentrations, leading to a shortening of the Debye length and thus a decreasing importance of any stabilising electrostatic interactions [118]. Methods for reducing adhesion forces in microrobotics are based around reducing contact area between objects [112,119].…”

Section: Optical Microrobots: Achievements To Date and Challengesmentioning

confidence: 99%

Optical Micromachines for Biological Studies

2020

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Optical tweezers have been used for biological studies since shortly after their inception. However, over the years research has suggested that the intense laser light used to create optical traps may damage the specimens being studied. This review aims to provide a brief overview of optical tweezers and the possible mechanisms for damage, and more importantly examines the role of optical micromachines as tools for biological studies. This review covers the achievements to date in the field of optical micromachines: improvements in the ability to produce micromachines, including multi-body microrobots; and design considerations for both optical microrobots and the optical trapping set-up used for controlling them are all discussed. The review focuses especially on the role of micromachines in biological research, and explores some of the potential that the technology has in this area.

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Section: Optical Microrobots: Achievements To Date and Challengesmentioning

confidence: 99%

Optical Micromachines for Biological Studies

2020

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“…Both parts of the micromachine are made from the same material, and immersed in the same fluid, and so it is assumed that the charge on the surfaces will be similar, and consequently repulsive. The expression for this interaction relies on the Debye length [19], as can be seen in (2), which gives the electrostatic force between two identical spheres, positioned a distance x apart, where x < 2R. In this equation R is the diameter of the particles, Z is the surface charge, κ −1 is the Debye length, 0 is the permittivity of free space, r is the relative permittivity and e c is the elementary charge.…”

Section: A Theorymentioning

confidence: 99%

“…This is important as the ionic strength of the surrounding medium has been demonstrated to affect the properties of biological samples; for instance the elasticity of DNA is affected by the amount of salt in the medium [18]. Salts screen repulsive electrostatic interactions between objects due to reduction of the Debye length [19], thus, adhesion between parts of multicomponent micromanipulators becomes more of an issue as salt increases. This work aims to determine the geometry required for levers with equal-length arms to function in tris-buffered saline (TBS), which has a molarity of 150 mMol sodium chloride (NaCl), and contains 45 mMol of Tris and hydrochloric acid in order to maintain a slightly alkaline pH of 7.5.…”

Section: Introductionmentioning

confidence: 99%

Design of Optical Micromachines for Use in Biologically Relevant Environments

Andrew

Fan

Raudsepp

et al. 2020

2020 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM)

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Advances in nanofabrication over the past twenty years have enabled the creation and use of ever-more interesting and useful micromachines. Optical micromachines are a particularly attractive subset of these for researchers in biological and soft-matter sciences, due to their potential to aid in optical tweezer studies of laser-sensitive samples. However, the development of multi-component micromachines is made difficult due to the dominance of surface forces at this scale, which is made all the more relevant in the high-salt concentrations used for biological studies. This study concerns the design of simple, first-class lever micromachines for use in environments with different salt concentrations, in an attempt to provide a guideline for design requirements of functional optical micromachines for use in physiological conditions.

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“…Optical tweezers (OT) are powerful tools that use focused laser light to trap and manipulate tiny objects (submicrometer to micrometer scale) without engaging in any mechanical contact. , This technology enables not only the noninvasive manipulation of samples in solution such as living cells and colloidal particles but also the single-molecule force spectroscopy at the surface of optically trapped samples. − In the colloidal dispersions, the interparticle force that occurs as two optically trapped particles become close to or apart from each other can be monitored as a function of the separation distance with the OT system. By taking advantage of this system, the interaction forces between various microparticles including the emulsion droplets have been studied under various conditions. − …”

Section: Introductionmentioning

confidence: 99%

Terminal Sequence-Specific Interparticle Attraction between DNA Duplex-Carrying Polystyrene Microparticles in Aqueous Salt Solution Assessed by Optical Tweezers

2021

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The dispersion behavior of DNA duplex-carrying colloidal particles in aqueous high-salt solutions shows extraordinary selectivity against the duplex terminal sequence. We investigated the interparticle force between DNA duplex-carrying polystyrene (dsDNA-PS) microparticles in aqueous salt solutions and examined their behavior in relation to the duplex terminal sequences. Force−distance (F−D) curves for a pair of dsDNA-PS particles were recorded with a dual-beam optical tweezers system with the two optically trapped particles closely approaching each other. Interestingly, only 3− 5% of the oligo-DNA strands on the dsDNA-PS particles formed a duplex with complementary DNAs, and the F−D curves showed a distinct specificity to the duplex terminal sequences in the interparticle force at a high-NaCl concentration; a clear attraction peak was observed in F−D curves only when the duplex terminal was a complementary base pair. The attractive strength reached 2.6 ± 0.5 pN at 500 mM NaCl and 4.3 ± 1.0 pN at 750 mM NaCl. By sharp contrast, no significant attraction occurred for the particles with mismatched duplex terminals even at 750 mM NaCl. Similar duplex terminal-specificity in the interparticle force was also confirmed for dsDNA-PS particles in divalent MgCl 2 solutions. Considering that the duplex terminal sequences on the dsDNA-PS particles showed only a negligible difference in their surface charges under identical salt conditions, we concluded that the interparticle attraction observed only for the dsDNA-PS particles with complementary duplex terminals is attributable to the salt-facilitated stacking interaction between the paired terminal nucleobases (i.e., blunt-end stacking) on the dsDNA-PS surfaces. Our results thus demonstrate the occurrence of a duplex terminal-specific interparticle force between dsDNA-PS particles under high-salt conditions.

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Measuring the interaction between a pair of emulsion droplets using dual-trap optical tweezers

Abstract: Force–separation curves measured from a singe pair of emulsion droplets as a function of salt concentration (fits are DLVO theory).

Cited by 18 publications

References 24 publications

Optical Micromachines for Biological Studies

Optical Micromachines for Biological Studies

Design of Optical Micromachines for Use in Biologically Relevant Environments

Terminal Sequence-Specific Interparticle Attraction between DNA Duplex-Carrying Polystyrene Microparticles in Aqueous Salt Solution Assessed by Optical Tweezers

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