Conference Agenda

Large cell clusters, such as organoids, cancer spheroids or developing embryos are often optically too opaque for imaging under illumination from only one side. Rotating or re-orienting the sample for multi-angle illumination is a solution to this problem, in the best case enabling 3D tomographic reconstruction of the refractive index distribution. Tailored optical and acoustic fields  can exert controlled forces on microscopic biomedical samples in suspension in a non-contact way. Large and therefore heavy particles, however, can only be levitated by acoustic forces - optical tweezers could not handle them without adverse high-power effects. By tuning standing MHz ultrasound waves it is possible to rotate or re-orient a sample inside a micro-fluidic chamber around one or more chosen axes perpendicular to the optical imaging direction, thus avoiding the ‘missing-cone’ problem which commonly leads to artifacts. As examples, the 3D reconstruction of a levitated zebrafish larva by optical coherence tomography (OCT) and of cell clusters by optical diffraction tomography (ODT) will be presented.

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