Microscale Flow Visualization

Sinton D (2004) Microscale flow visualization. Microfluid Nanofluid 1(1) 2—21... 

Flow visualization is a branch of fluid mechanics that provides visual perception of the dynamic behavior of fluids flows. The fundamental principle of any flow visualization technique lies in the detection of fluid transport by altering the fluid properties while leaving the fluid motion unaltered. Microscale flow visualization focuses on imaging microfluidic flows, with the most common techniques broadly classified into particle-based and scalar-based methods. 

Microscale flow visualization has played a key role in the development of the microfluidics and LOC fields. It is central to fundamental understanding of microflows, developing novel microfluidic processes, investigating nonideal and nonlinear behaviors, and providing data for numerical simulations. Many microfluidic applications such as mixing, pumping, and filtering require flow visualization to characterize device efficiency. To date, most microscale flow... 

Particle-based flow visualization techniques introduce marker particles into the flow field to study the motion of the bulk by determining the velocity vectors associated with these particles. Laser Doppler velocimetiy (LDV), optical Doppler tomography (ODT), and particle image velocimetiy (PIV) are the different methods that have been developed in this regard. However, of these methods, microscale PIV (p-PlV) is the most well-developed and popular microscale flow visualization technique. 

Microscale Flow Visualization, Fig. 1 (a) Velocity profile across 175-pm-wide glass microchannel obtained by LDV [4]. (b) Velocity field across a 120-pm-wide acrylic microchannel, obtained experimentally with both PIV and PTV and compared with simulation data [18]... 

Microscale Flow Visualization, Fig. 3 Schematic illus- a known time delay, the flow velocity vectors can be trating the principle of flow characterization using PIV calculated technique. By calculating the displacement of a particle In... 

As mentioned earlier, most microscale flow visualization techniques have focused on determination of flow velocity in liquids (or velocimetry). Fluorescence-based techniques, e.g., LIF and PF, have been extensively used for this application. However, in this section, we will look at another microfluidic application for which the development of microscale flow visualization techniques have been critical-micromixing. 

The field of microscale flow visualization has been receiving wide attention in the recent years due to developments in microfluidics and LOCs. Most of the developed techniques are capable of high spatial and velocity resolution, with p-PIV and fluorescence imaging being the most widely used. 

Microscale Flow Visualization Particle Image Velocimetry (PIV) Shear Stress Sensors... 

Transport phenomena on the microscale have gained particular importance due to an increasing demand for more efficient and sustainable processes. Especially the bridge between nano- and micro technologies requires a deep understanding of multiscale coherences. Advances in microfluidic and nanofluidic technologies have been paralleled by advances in methods for direct optical measurement of transport phenomena on these scales. A variety of methods for microscale flow visualization have appeared and evolved since the late 1990s. These methods and their applications to date are reviewed here in detail, and in the context of the fundamental phenomena that they exploit and the fundamental phenomena that they are applied to measure. 

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