This is an article that I found interesting, when I attended in BIOMEMS lectures. So I made a presentation slide as a note. The paper highlights centrifugal microfluidic CD platform that use liquid equilibrium valve. Liquid equilibrium valve are consider passive valve. Article used: http://eprints.um.edu.my/9331/1/Novel_liquid_equilibrium_valving_on_centrifugal_microfluidic_CD_platform.pdf

1. Novel Liquid Equilibrium Valving on
Centrifugal Microfluidic CD
Platform
MUHAMMAD ALI AIZAT BIN ABU BAKAR
BIOMEDICAL ENGINEER
6th February 2022

2. What is
Centrifugal
Microfluidic CD
platform?
 Medical diagnostic tool
 Disc-shaped platforms with networks of microchannels
and chambers
 Instead of relying on external pump, it use spinning
technique to manipulate liquid dynamics.
 The flow rate and direction can be controlled by
controlling the spinning speed of the microfluidic CD

3. Application
 Enzyme-Linked Immunosorbent Assay (ELISA) for
dengue detection
 DNA purification
 Polymerase chain reactions (PCR)
 Plasma separation

4. Material
PMMA PSA
Poly-methyl methacrylate
(Acrylic)
Polyester film resin-bonded
to aluminium oxide
Transparent, lightweight
thermoplastic
Pressure sensitive adhesive
*Depends on design

5. Typeof force
 Centrifugal force
 Capillary force
Responsible for pumping and stopping liquid flow in
microfluidic CD.

6. Typeof
parameter Centrifugal force
 Force needed to push liquid towards outer ring of CD

7. Typeof
parameter  p = density of liquid
 w = rotational speed of CD (rads-1)
 Δr = diff. btwn top and bottom liquid levels at rest,
respective to centre of CD
 r = average distance of liquid from centre of CD

8. Typeof
parameter Burst frequency
 Spinning speed of CD where the liquid will burst out of
source chamber

9. Typeof valve
Passive valve
 Valves that control liquid movement without involving
movable part
 Example: capillary valves, siphon valves
Advantages:
 No external trigger/force is required to start/stop liquid
movement
Disadvantages:
 Moderate precision in control of liquid movement on
the CD

10. Typeof valve
Active valve
 Valves that control liquid movement using external
actuations
 Example: wax valves, ice valves
Advantages:
 Sealing of liquid on the microfluidic CD during long
period of storage
 Accurate control of liquid movement on the CD
Disadvantages:
 Requires external trigger for activation

11. Structure
Source chamber
 As sample storage before
centrifugation
Destination chamber
 As sample storage after
centrifugation
Venting chamber
 To manipulate burst
frequency by increasing
liquid height in venting
chamber

12. Process
*using liquid equilibrium valve
(passive valve)

13. Process
1. Low spinning speed, below
burst frequency
 Source chamber pressure <
venting chamber pressure

14. Process
2. High spinning speed, below
burst frequency
 Source chamber pressure ->
destination chamber pressure
 Venting chamber pressure ->
destination chamber pressure
 Result: Air compression
 Source liquid -> microchannel
 Increasing destination
chamber pressure

15. Process
3. Higher spinning speed,
exceed/equal to burst
frequency
 Source chamber pressure >
venting chamber pressure
 Microchannel liquid ->
destination chamber

16. Advantage
By implementing this valving method;
 Only a compact and accurately-controlled motor is
required
 Without the need for external syringe pump
 Eliminate environmental contamination from external
pumping
 Minimize air bubbles from external pumping
mechanisms

17. Disadvantage
The permanent radial outward direction of the
centrifugal force can;
 limit the range of applicable processes
 limit complexity of applicable processes

18. Reference
 Al-Halhouli, A., Far, B. E., Albagdady, A., & Al-Faqheri, W.
(2020). Development of Active Centrifugal Pump for
Microfluidic CD Platforms. Micromachines, 11(2), 140.
https://doi.org/10.3390/mi11020140
 Al-Faqheri W, Ibrahim F, Thio TH, Arof H, Madou M. Novel
liquid equilibrium valving on centrifugal microfluidic CD
platform. Annu Int Conf IEEE Eng Med Biol Soc.
2013;2013:5509-12. doi: 10.1109/EMBC.2013.6610797.
PMID: 24110984.