1. Microfluidics

2. Microfluidics
Microfluidics is the science of designing, manufacturing, and formulating devices and processes that deal with volumes of fluid on the order of nanoliters (symbolized nl and representing units of liter) or picoliters (symbolized pl and representing units of liter).

3. Why use microfluidics?

4. Why use microfluidics? Sample savings – nL of enzyme, not mL
Faster analyses – can heat, cool small volumes quickly
Integration – combine lots of steps onto a single device
Novel physics – diffusion, surface tension, and surface effects dominate
This can actually lead to faster reactions!

5. Motivation for Microfluidics
Automation
Integration
Miniaturization
Test tubes
Automation
Integration
Miniaturization
Robotics
Automation
Integration
Miniaturization
Microfluidics

6. Timeline of the evolution of microfluidic technology

7. Microfluidics

8. Microfluidics field of application

9. The behavior of fluids at the microscale
Effects of micro domain
lamniar flow
surface tension
electrowetting
diffusion

10. Laminar flow Opposite to turbulent flow
Low Reynold’s number (inertial to viscous forces)
Flow follows certain paths
Mixing typically does not occur
Predict the position of a particle

11. Laminar flow

12. Physics of Mixing
Many microfluidic systems create flows with no stirring.
When there is very little mixing, multiple streams of fluid can be used to pattern the chemical species inside a microchannel
The widths of the fluid streams are algebraic functions of the flow rates

13. Microfluidic Mixing
Low mixing enables patterning, but high mixing is required for chemical assays
Mixing is enhanced by “stirring”, or increasing the interfacial area between regions of different scalar concentration, i.e., shortening diffusion length scales

14. Surface Tension
Because of the increased number of interactions, molecules in the bulk of solution are at a lower energy state than those on the surface.
Molecules in any medium experience an attractive force with other molecules.
Mainly hydrogen bonds for polar molecules
Van der Waals forces for other molecules
Molecules in the interiour of a liquid
Molecules at the surface of a liquid
Imbalance of this attractive force at an interface leads to surface tension

15. Capillary Action
Capillary action refers to the movement of liquid through thin tubes, not a specific force.
Several effects can contribute to capillary action, all of which relate to surface tension

16. Electrowetting
Electrical modulation of the solid-liquid interfacial tension
No Potential
A droplet on a hydrophobic surface originally has a large contact angle.
Applied Potential
The droplet’s surface energy increases, which results in a reduced contact angle. The droplet now wets the surface.

17. Microfluidics
Continuous-flow : Permanently etched microchannels, micropumps and microvalves
Digital microfluidic : Manipulation of liquids as discrete droplets
Multiplexing
Mixing: Static, Diffusion Limited
Biosensors:
Optical: SPR, Fluorescence etc.
Electrochemical: Amperometric, Potentiometric etc.

18. Material for the fabrication of microfluidic channels
Silicon/ Si compounds
Classical MEMS approach
Etching involved
Polymer/ plastics
New methods
Easy fabrication

19. Test 1
Test 2
Test 1
Test 2
Test 3
Test 4
Test 3
Test 4

20. Sample Chip Design Top View Side View
We start with a chip design. Below is a simple sample design that we’ll be using as an example.
Top View
70µm x 7µm Channel
70µm x 1µm Channel
Peristaltic Pump
Side View
Hole-Punched Inlet

21. Fabrication by laser abalition Micromachining of silicon and glass

22. Photolithography Mask Positive Resist Negative Resist
There are two types of photoresist:
Positive: Exposure to UV light removes resist
Negative: Exposure to UV light maintains resist
Mask
Positive Resist
Negative Resist

23. Polymers Inexpensive Flexible Easily molded
Surface properties easily modified
Improved biocompatibility

24. Polymethyl methacrylate (PMMA)
Often use as an alternative to glass
Easily scratched
Not malleable
It can come in the form of a powder mixed
with liquid methyl methacrylate, which is an
irritand and possible carcinogen

25. Polydimethylsiloxane (PDMS)
Silicon-based organic polymer
Non toxic
Non flammable
Gas permeable
Most organic solvents can diffuse and
cause it to swell

26. Teflon Polytetrafluoroethylene (PTFE) Synthetic fluoropolymer
Non reactive
Fluorinated Ethylene Propylene (FEP)
Excellent electrical properties
Flam resistant
Excelent chemical resistance

27. Why Teflon Excellent chemical resistance High temperature tolerance
Low gas permeability

28. Replica molding

29. Embossing

30. Injection Molding

31. Laser Ablation

32. Fabrication of nanofluidic with electrospun nanofibers

33. Nanofluidics
Nanofluidics is the study of the behavior, manipulation, and control of fluids that are confined to structures of nanometer (typically 1-100 nm) characteristic dimensions (1 nm = 10−9 m).
Exhibit physical behaviors not observed in larger structures, such as those of micrometer dimensions and above,
Increased viscosity near the pore wall
May effect changes in thermodynamic properties and
May also alter the chemical reactivity of species at the fluid-solid interface

34. Flow behavior in nanofluidics

35. Nanocircuitries :Examples of NEMS

36. Micro Total Analysis system (uTAS)

37. Components Sample injection Puming Sepration Mixing Reaction Trasport
Detection

38. Microfluidic flow

39. Pumps

40. Micromixer

41. Flow (electroosmotic and pressure driven)
Electroosmotic flow is developed in a capillary when the capillary has electrical charges, the fluids are electrolytes and external electric fields are applied

42. Detection

43. Microfluidic application
Integrated microfluidic devices for DNA analysis
Polymerase chain reaction (PCR)
Integrated PCR and separation based detection
Integrated DNA hybridization
Devices for separation based detection
General capillary electrophoresis
Devices for cell handling, sorting and general analysis
Cell handling and cytometry
Devices for protein based applications
Protein digestion, identification and synthesis
Integrated devices for chemical analysis, detection and processing
Integrated microreactors
Chemical detection and monitoring devices
Integrated microfluidic devices for immunoassay

44. Devices for miniaturized PCR
PCR the most widely used process in biotechnology for DNA fragments amplification
Polymer devices for continuous-flow PCR

45. Summary of microfluidic motivation

46. Challenges with Lab-on-Chip

48. Application areas

49. What are the main types of biochips?
Passive (array):
all liquid handling functions are performed by
the instrument. The disposable is simply a
patterned substrate.
Active (lab-on-chip, m-TAS):
some active functions are performed by the
chip itself. These may include flow control,
pumping, separations where necessary, and
even detection.

50. Biochips DNA Protein Microarray Cell Fluid handling Pumping LoC
Microfluidics
DNA
Protein
Cell
Fluid handling
Sample precondition
Mixing
Reaction
Separation
Pumping
Concentration
Dilution
Extraction
Active Mixer
Passive Mixer
Chemical
Enzymatic
Immunoassay
Electrophoresis

52. Some companies

53. Lab-on-Chip for developping countries

54. Point of care (POC)

55. The Not-so-Distant Future
2008
PDA
2308??
Paramount