Richard Bergman

Self-referencing a single waveguide grating sensor in a micron-sized deep flow chamber for label-free biomolecular binding assays

In order to allow the design of increasingly sensitive label-free biosensors, compensation of environmental fluctuations is emerging as the dominant hurdle. The system and technique presented here utilize a unique combination of microfluidics, optical instrumentation, and image processing to provide a reference signal for each label-free biomolecular binding assay. Moreover, this reference signal is generated from the same sensor used to detect the biomolecular binding events. In this manner, the reference signal and the binding signal share nearly all common-mode noise sources (temperature, pressure, vibration, etc.) and their subtraction leaves the purest binding signal possible. Computational fluid dynamic simulations have been used to validate the flow behavior and thermal characteristics of the fluids inside the sensing region. This system has been demonstrated in simple bulk refractive index tests, as well as small molecule (biotin/streptavidin) binding experiments. The ability to perform not only simple binding but also control experiments has been discussed, indicating the wide applicability of the technique.

Numerical Mixing Analysis of a Vaned Circular Micromixer

Mixing of fluids is a common and often critical step in microfluidic systems. In typical large scale processes turbulence greatly speeds the mixing process. At the mini and micro-scales, however, the flow is laminar and the benefits of turbulent mixing are not present. Mixing at the mini- and micro-scales tends to become a more highly engineered process of bringing fluids together in predictable ways to achieve a predetermined and acceptable level of mixing. This paper summarizes a numerical analysis of the mixing performance of a vaned circular micromixer. A newly developed mixing metric suitable for reacting fluids is developed for this study. Applying the basic steps of stretching, cutting, and stacking to effect mixing, a useful micromixer is analyzed numerically for its mixing efficiency. A parametric study of flow and viscosity indicate that a flow Re of 12 or higher is sufficient to achieve effective and rapid mixing in this device.Copyright