Three-dimensional force calibration of optical tweezers

Singer, Wolfgang; Bernet, Stefan; Hecker, N. E.; Ritsch‐Marte, Monika

doi:10.1080/095003400750039799

Cited by 17 publications

(15 citation statements)

References 6 publications

(10 reference statements)

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“…63,64 As shown in Fig. 11, we have verified that this is indeed the case for κ and β in our setup by measuring power spectra of a free bead at a fixed stage displacement of 2 μm for several laser intensities.…”

Section: Dna Force-versus-extension At Several Laser Powersmentioning

confidence: 64%

Practical axial optical trapping

Mack

Schlingman

Regan

et al. 2012

Review of Scientific Instruments

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We describe a new method for calibrating optical trapping measurements in which tension is applied in the direction of the laser beam to a molecule tethered between a surface and an optically trapped bead. Specifically, we present a generally-applicable procedure for converting from the measured scattering intensity and the measured stage displacement to applied tension and bead-coverslip separation, using measurements of the light intensity scattered from an untethered, trapped bead. Our calibration accounts for a number of effects, including aberrations and the interference of forwardreflected bead-scattered light with the trapping beam. To demonstrate the accuracy of our method, we show measurements of the DNA force-versus-extension relation using a range of laser intensities, and show that these measurements match the expected extensible wormlike-chain (WLC) behavior. Finally, we also demonstrate a force-clamp, in which the tension in a tether is held fixed while the extension varies as a result of molecular events.

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Section: Dna Force-versus-extension At Several Laser Powersmentioning

confidence: 64%

Practical axial optical trapping

Mack

Schlingman

Regan

et al. 2012

Review of Scientific Instruments

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“…A special feature of the BS detection compared to the FS case is that the same lens is used both for trapping and for collecting the scattering light. In the literature, the use of the BS light for position and force detection is mentioned [26][27][28][29][30][31] but, contrary to the FS light detection, has not been discussed extensively.…”

Section: Introductionmentioning

confidence: 99%

Backscattering position detection for photonic force microscopy

Volpe

Kozyreff

Petrov

2007

Journal of Applied Physics

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An optically trapped particle is an extremely sensitive probe for the measurement of pico-and femto-Newton forces between the particle and its environment in microscopic systems ͑photonic force microscopy͒. A typical setup comprises an optical trap, which holds the probe, and a position sensing system, which uses the scattering of a beam illuminating the probe. Usually the position is accurately determined by measuring the deflection of the forward-scattered light transmitted through the probe. However, geometrical constraints may prevent access to this side of the trap, forcing one to make use of the backscattered light instead. A theory is presented together with numerical results that describes the use of the backscattered light for position detection. With a Mie-Debye approach, we compute the total ͑incident plus scattered͒ field and follow its evolution as it is collected by the condenser lenses and projected onto the position detectors and the responses of position sensitive detectors and quadrant photodetectors to the displacement of the probe in the optical trap, both in forward and backward configurations. We find out that in the case of backward detection, for both types of detectors the displacement sensitivity can change sign as a function of the probe size and is null for some critical sizes. In addition, we study the influence of the numerical aperture of the detection system, polarization, and the cross talk between position measurements in orthogonal directions. We finally discuss how these features should be taken into account in experimental designs.

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“…The method is based on the measurement of trapping dynamics between two traps and is described in Ref. 15 for twobeam laser tweezers. In our single-beam layout, the stiffness can be estimated in the same way by use of a two-site pattern of the multiple-trap option, with a distance between sites approximately equal to the diameter of the bead (d).…”

Section: Multitrapping Stiffness Measurementmentioning

confidence: 99%

Dynamics of multiple trapping by a single-beam laser tweezer

et al. 2005

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A multiple-trap single-beam scanning laser tweezer system was developed and characterized. Different stationary and mobile multiple-trap modes were generated for polystyrene beads in a water environment. Trapping efficiency and stability were investigated for several dynamic parameters such as transition time between the sites, waiting time on a single site, number of trapping sites, and IR laser power. Optimal parameters for efficient generation of complex arrays and matrices were determined. We demonstrate an example of a single laser beam multiple-trap application by measuring the trap's stiffness in water for our laser tweezer setup.

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Three-dimensional force calibration of optical tweezers

Cited by 17 publications

References 6 publications

Practical axial optical trapping

Practical axial optical trapping

Backscattering position detection for photonic force microscopy

Dynamics of multiple trapping by a single-beam laser tweezer

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