dorsal/arxiv
View SchemaTowards absolute calibration of optical tweezers
| Authors | N. B. Viana, M. S. Rocha, O. N. Mesquita, A. Mazolli, P. A. Maia Neto, H. M. Nussenzveig |
|---|---|
| Categories | |
| ArXiv ID | physics/0612252 |
| URL | https://arxiv.org/abs/physics/0612252 |
| DOI | 10.1063/1.2189148 |
Abstract
Aiming at absolute force calibration of optical tweezers, following a critical review of proposed theoretical models, we present and test the results of MDSA (Mie-Debye-Spherical Aberration) theory, an extension of a previous (MD) model, taking account of spherical aberration at the glass/water interface. This first-principles theory is formulated entirely in terms of experimentally accessible parameters (none adjustable). Careful experimental tests of the MDSA theory, undertaken at two laboratories, with very different setups, are described. A detailed description is given of the procedures employed to measure laser beam waist, local beam power at the transparent microspheres trapped by the tweezers, microsphere radius and the trap transverse stiffness, as a function of radius and height in the (inverted microscope) sample chamber. We find generally very good agreement with MDSA theory predictions, for a wide size range, from the Rayleigh domain to large radii, including the values most often employed in practice, and at different chamber heights, both with objective overfilling and underfilling. The results asymptotically approach geometrical optics in the mean over size intervals, as they should, and this already happens for size parameters not much larger than unity. MDSA predictions for the trapping threshold, position of stiffness peak, stiffness variation with height, multiple equilibrium points and `hopping' effects among them are verified. Remaining discrepancies are ascribed to focus degradation, possibly arising from objective aberrations in the infrared, not yet included in MDSA theory.
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"abstract": "Aiming at absolute force calibration of optical tweezers, following a\ncritical review of proposed theoretical models, we present and test the results\nof MDSA (Mie-Debye-Spherical Aberration) theory, an extension of a previous\n(MD) model, taking account of spherical aberration at the glass/water\ninterface. This first-principles theory is formulated entirely in terms of\nexperimentally accessible parameters (none adjustable). Careful experimental\ntests of the MDSA theory, undertaken at two laboratories, with very different\nsetups, are described. A detailed description is given of the procedures\nemployed to measure laser beam waist, local beam power at the transparent\nmicrospheres trapped by the tweezers, microsphere radius and the trap\ntransverse stiffness, as a function of radius and height in the (inverted\nmicroscope) sample chamber. We find generally very good agreement with MDSA\ntheory predictions, for a wide size range, from the Rayleigh domain to large\nradii, including the values most often employed in practice, and at different\nchamber heights, both with objective overfilling and underfilling. The results\nasymptotically approach geometrical optics in the mean over size intervals, as\nthey should, and this already happens for size parameters not much larger than\nunity. MDSA predictions for the trapping threshold, position of stiffness peak,\nstiffness variation with height, multiple equilibrium points and `hopping\u0027\neffects among them are verified. Remaining discrepancies are ascribed to focus\ndegradation, possibly arising from objective aberrations in the infrared, not\nyet included in MDSA theory.",
"arxiv_id": "physics/0612252",
"authors": [
"N. B. Viana",
"M. S. Rocha",
"O. N. Mesquita",
"A. Mazolli",
"P. A. Maia Neto",
"H. M. Nussenzveig"
],
"categories": [
"physics.optics",
"physics.bio-ph"
],
"doi": "10.1063/1.2189148",
"title": "Towards absolute calibration of optical tweezers",
"url": "https://arxiv.org/abs/physics/0612252"
},
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