Towards absolute calibration of optical tweezers.
Phys Rev E Stat Nonlin Soft Matter Phys
; 75(2 Pt 1): 021914, 2007 Feb.
Article
em En
| MEDLINE
| ID: mdl-17358374
ABSTRACT
Aiming at absolute force calibration of optical tweezers, following a critical review of proposed theoretical models, we present and test the results of Mie-Debye-spherical aberration (MDSA) 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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Base de dados:
MEDLINE
Assunto principal:
Algoritmos
/
Calibragem
/
Análise de Falha de Equipamento
/
Pinças Ópticas
/
Modelos Teóricos
Tipo de estudo:
Evaluation_studies
/
Prognostic_studies
País/Região como assunto:
America do sul
/
Brasil
Idioma:
En
Revista:
Phys Rev E Stat Nonlin Soft Matter Phys
Assunto da revista:
BIOFISICA
/
FISIOLOGIA
Ano de publicação:
2007
Tipo de documento:
Article
País de afiliação:
Brasil