10 Summary
Overview of the Course
At a first glance, macro- and microfluidics seem to be very similar but after a closer look we find substantial differences.
In this course we have learned about different fluid properties and the underlying physics that are applied to flow on different scales. The flow properties of most flows can be replicated on different scales when match-ing the related dimensionless numbers, like the Reynolds or Womersley number. Nevertheless, it is important to consider special factors that only occur on very small scales like the capillary effect in narrow tubes.
Macro and Micro-fluidics
Apply the following points to compare and contrast the differences between:
Macrofluidics
- Importance of scale – Waterbug example > weight ^3, area ^2 and surface tension ^1
- Types of fluid (Newtonian vs non-Newtonian with shear thinning, thickening) and their properties ( density, viscosity, etc.)
- Most important dimensionless number in fluid dynamics? Re = inertia / viscous forces, hydraulic diameter, entrance length
- Name important characteristics for the biological domain!
- Why does a giraffes head doesn’t explode? What equation can we use to describe this principal?
Microfluidics
- What does microfluidics mean? Why is it so relevant for biological applications?
- Why do we go small?
- What can be achieved with microbiodevices?
- Can you name examples of applications?
- Industry and future opportunities
The following questions cover topics across macro and micro-fluidics.
Biofluidics
When applying knowledge about microfluidics to biological fluids, many assumptions need to be adjusted to match the properties.
Key Example: Blood Flow
Blood in particular is an interesting but difficult fluid to work with be-cause of its non-Newtonian behaviour and the unsteady, pulsatile flow in a cardio-vascular system. Also, the fact that blood flow is pseudo-parabolic is important to consider because it affects the entrance length into an artery before being a fully developed flow.
The following questions cover topics across biofluidics:
Micro and Bio-fluidic Devices and Fabrication
To be able to understand and simulate micro and biofluidic flows, studies in silico and in vitro are necessary. With the help of computational fluid dynamics (CFD) and Laser Doppler Velocimetry (LDV), as well as different flow and shear stress measuring techniques it is possible to predict flows in the human body. Because of that, a vast variety of disease conditions can be understood and partly prevented and implants for the human body can be optimised.
Investigating flows on micro- and nano scale through a simulation is rather easy in comparison to a real-life model. In this course we have discussed how and where it is possible to fabricate flow devices on small scales. Different fabrication techniques can be used like top-down, where larger materials are broken down, or bottom-up, where nanoscale structures are assembled. The fabrication is done in clean rooms.
Microfluidic devices can be used for a lot of different applications. Coupling properties like mechanics and electronics are important considerations. Other applications include stents, piezoelectric printers and microneedles.
The following questions cover topics across microdevice fabrication and applications:
In Vitro, In Vivo and In Silico
In vivo techniques like microscopy, phase contrast MRI or ultrasound can assess in body flows and are powerful complimentary tools.
In silico refers to the computational methods utilised to simulate microfluidic flow, such as computational fluid dynamics. During computational modelling, boundary conditions and assumptions pertaining to the vessel shape and type of flow must be identified before an accurate result can be achieved.
The following questions cover topics across in vivo, in vitro and in silico methods:
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