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dc.contributor.advisorKäs, Josef A.en
dc.creatorGuck, Jochen Reinholden
dc.date.accessioned2011-03-14T21:43:44Zen
dc.date.available2011-03-14T21:43:44Zen
dc.date.issued2001-12en
dc.identifier.urihttp://hdl.handle.net/2152/10501en
dc.descriptiontexten
dc.description.abstractWhen a laser beam is incident on the surface of a transparent object, the optical surface forces, generated by the interaction of the light with the material, are directed away from the denser material and normal to its surface. This physical phenomenon can be used to probe the mechanical properties of dielectric materials. This optical deformability was exploited for the measurement of cellular elasticities with a novel micromanipulation device based on a two-beam fiber-based laser trap, the optical stretcher, which can generate surface forces from 1 pN–1 nN at frequencies ranging from static experiments to several MHz. The feasibility of accurately determining the elastic properties of biological cells with the optical stretcher was demonstrated by stretching human erythrocytes. A simple ray-optics treatment was used to explain and quantify the stresses on the surface of the cell, while their resulting deformation was recorded by video viii microscopy. Subsequent analysis of these data, modeling the erythrocyte as a thin shell, resulted in a cortical shear modulus of (1.3 ± 0.5) × 10–5 Nm–1, which is in excellent agreement with literature values. This result validates the ray-optics treatment. Higher developed, eukaryotic cells have an extensive threedimensional cytoskeleton throughout their cytoplasm, which renders them much more resistant to deformation. Using the optical stretcher, human neutrophils, normal and malignantly transformed mouse fibroblasts, and rat precursor cells were successfully stretched. These cells could be distinguished based on their optical deformability, with less differentiated cells showing lower elastic strength. The viability of the cells stretched was not jeopardized even when irradiated with 1.4 W of 780 nm laser light in both beams. By incorporation into a microfluidic flow chamber, the optical stretcher has the potential to measure up to several cells per minute, taking the speed of cell elasticity measurements to a new level and predisposing it for applications in biomedical diagnostic applications. As examples, the implications for cancer diagnosis and stem cell sorting are discussed in detail. Other applications of optical surface forces are envisioned.
dc.format.mediumelectronicen
dc.language.isoengen
dc.rightsCopyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.en
dc.subjectMicroelectromechanical systemsen
dc.subjectErythrocytesen
dc.subjectCytology--Researchen
dc.subjectMicromechanicsen
dc.titleOptical deformability : micromechanics from cell research to biomedicineen
dc.description.departmentPhysicsen
thesis.degree.departmentPhysicsen
thesis.degree.disciplinePhysicsen
thesis.degree.grantorThe University of Texas at Austinen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen
dc.rights.restrictionRestricteden


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