The lack of an effective technique for three-dimensional flow visualization has limited the experimental exploration of the “coffee ring effect” to the two dimensional, top-down viewpoint. In this report, high-speed, cross-sectional imaging of the flow fields was obtained by using optical coherence tomography to track particle motion in an evaporating colloidal water drop. This approach enables z-dimensional mapping of primary and secondary flow fields and changes in these fields over time. These sectional images show that 1μm diameter polystyrene particles have a highly non-uniform vertical distribution with particles accumulating at both the air-water interface and water-glass interface during drop ...

We investigated the feasibility of constructing an implantable optical-based sensor for seminoninvasive continuous monitoring of analytes. In this novel sensor, analyte concentration-dependent changes induced in the degree of optical turbidity of the sensing element can be accurately monitored by optical coherence tomography (OCT), an interferometric technique. To demonstrate proof-of-concept, we engineered a sensor for monitoring glucose concentration that enabled us to quantitatively monitor the glucose-specific changes induced in bulk scattering (turbidity) of the sensor. The sensor consists of a glucose-permeable membrane housing that contains a suspension of macroporous hydrogel particles and concanavalin A (ConA), a glucose-specific lectin, that are designed ...