Surface imaging using holographic optical tweezers

Phillips, D., Grieve, J.A., Olof, S.N., Kocher, S.J., Bowman, R., Padgett, M.J. , Miles, M.J. and Carberry, D.M. (2011) Surface imaging using holographic optical tweezers. Nanotechnology, 22(28), p. 285503. (doi: 10.1088/0957-4484/22/28/285503)

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We present an imaging technique using an optically trapped cigar-shaped probe controlled using holographic optical tweezers. The probe is raster scanned over a surface, allowing an image to be taken in a manner analogous to scanning probe microscopy (SPM), with automatic closed loop feedback control provided by analysis of the probe position recorded using a high speed CMOS camera. The probe is held using two optical traps centred at least 10 µm from the ends, minimizing laser illumination of the tip, so reducing the chance of optical damage to delicate samples. The technique imparts less force on samples than contact SPM techniques, and allows highly curved and strongly scattering samples to be imaged, which present difficulties for imaging using photonic force microscopy. To calibrate our technique, we first image a known sample—the interface between two 8 µm polystyrene beads. We then demonstrate the advantages of this technique by imaging the surface of the soft alga <i>Pseudopediastrum</i>. The scattering force of our laser applied directly onto this sample is enough to remove it from the surface, but we can use our technique to image the algal surface with minimal disruption while it is alive, not adhered and in physiological conditions. The resolution is currently equivalent to confocal microscopy, but as our technique is not diffraction limited, there is scope for significant improvement by reducing the tip diameter and limiting the thermal motio

Item Type:Articles
Glasgow Author(s) Enlighten ID:Padgett, Professor Miles and Bowman, Mr Richard and Phillips, Dr David
Authors: Phillips, D., Grieve, J.A., Olof, S.N., Kocher, S.J., Bowman, R., Padgett, M.J., Miles, M.J., and Carberry, D.M.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Nanotechnology
Publisher:IOP Publishing
ISSN (Online):1361-6528
Published Online:01 January 2011

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
542471Optical Atomic Force MicroscopyMiles PadgettEngineering & Physical Sciences Research Council (EPSRC)EP/I007822/1Physics and Astronomy