FLOW MODELING AND VISUALIZATION IN MICROFLUIDICS
Prof. Wei-Hsin Tien, National Taiwan University of Science and Technology
Dr. Rune Barnkob, Technical University of Munich
Prof. Henrik Bruus, Technical University of Denmark
Prof. Yuki Minamoto, Nora Scientific

Workshop Description:
In the process of developing lab-on-a-chip systems, computational and experimental tools for modeling and visualization of fluid flow are essential for characterization of microfluidic flows and determine forces acting on suspended particles. These tools used to be difficult and expensive to setup and required specific knowledge to operate. With the help of technological advances and efforts from the research community, they become more affordable and accessible nowadays.

The aim of this workshop is therefore to introduce the participants of MicroTAS 2020 to some of the most popular flow visualization and modeling tools, particularly particle image velocimetry (PIV), particle tracking velocimetry (PTV), and multi-physics simulation with finite element method (FEM). The participants will learn the fundamental knowledge and tools for performing 2D PIV and 2D/3D PTV analyses on their own microfluidic systems. Here, free tools such as PIVLab and DefocusTracker will be used to help the participants to gain hand-on experiences. For modeling, the participants will be introduced to the fundamental aspects of theoretical microfluidics as well as to the basic principles and constrains of computational fluid dynamics (CFD). The participants will learn to use a handy and free CFD software, Flowsquare+.

Overview of Material to Be Covered and What Attendees Can Expect to Take Away From the Workshop:
This workshop part contains 4 lectures:

1. The first lecture focuses on the classic 2-D flow visualization technique, PIV and PTV. In-plane 2D PIV and PTV analyses with both theoretical and practical aspects will be discussed, as well as an introduction to and work-through examples with the freely-available MATLAB PIVlab toolbox (https://pivlab.blogspot.com/).
2. The second lecture focuses on a general 3-D particle tracking method. In particular, the lecture will focus on the fundamental and practical aspects of General Defocusing Particle Tracking (GDPT), which is a single-camera 3D particle tracking based on particle-image defocusing principle and relies only on standard microfluidics laboratory equipment: microscope, light source, and camera. Examples of application of GDPT will be given together with an introduction to the freely-available and open-source MATLAB GDPT toolbox DefocusTracker (to be published summer 2020, https://defocustracking.com/). Additionally, the participants will be provided with work-through examples of real experimental datasets for a hands-on experience with GDPT and DefocusTracker.
3. The third lecture gives an introduction to the basics of theoretical microfluidics. It will provide the participants with important information needed to get started in modeling microfluidic systems. In particular, often-encountered governing equations and boundary conditions will be highlighted, and suggestions for modeling verification and validation will be given. On www.fysik.dtu.dk/microfluidics, more than 115 peer-reviewed papers and 50 PhD/MSc theses on various aspects of theoretical microfluidics are available for download, including topics such as acoustofluidics, electrokinetics, magnetophoresis, cell handling, flow in bio-microreactors and plants, osmosis, topology optimization, two-phase flow, nanofluidics, and ac microfluidics.
4. The fourth lecture will give general knowledge about performing CFD and judging the reasonability of colorful images generated by the CFD software, Flowsquare+ (https://fsp.norasci.com/en/). It is a handy (possibly the handiest) CFD tool and is used in undergraduate CFD courses at many universities. Thus, the course material is also good for the young researchers who are considering joining universities as academic staff future.

Who Should Attend:
The workshop is intended for a broad audience, such as biologists, chemists, and engineers, and is particularly suited for scientists with few or no experience in velocimetry that need easy-to-use, yet powerful tools for performing 2D and 3D PIV/PTV analysis in microfluidic applications. It is also suitable for those who are interested in establishing computational models based on experimental results, but have no idea or very few experiences of CFD, or seeking a good CFD tool to teach their students CFD in university / summer school lectures.

Participants Will Need the Following:

1. Computer with MATLAB (if they want to run the provided work-through examples), preferably with PIVlab and DefocusTracker downloaded and installed.
2. PC-based computers with a Windows 10 environment is required for running Flowsquare+. It can be downloaded from https://fsp.norasci.com/en/. All users can use the software under the trial license for free without license activation. Students can apply a free student license.