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Microfluidic Systems in
Environmental Monitoring
Stephan Warnat, PhD Mechanical and Industrial Engineering,
Montana State University 20. October 2017
Water Monitoring Water quality described by: • Physical • Chemical • Biological characteristics of water. Measurements of water quality indicate health of ecosystem.
Remote sampling2,3 1 http://www.shorelinewa.gov/government/departments/public-works/surface-water-utility/water-quality-monitoring 2 www.in-situ.com 3 www.upstatefreshwater.org
Manual sampling1
Expensive Low spatial and temporal resolution
Determining Water Quality Parameters
Physical
• Temperature
• Pressure
• Flow
Biological
• Cell count
• DNA/RNA
• Fluorescence
Chemical
• pH
• pCO2
• Conductivity
Harmful Algae Bloom
T. Sellers Dramatic Algal Blooms in Lake of the Woods Call for Dramatic Action. 01.12.2015 http://tpwd.texas.gov/landwater/water/environconcerns/hab/ga/killphotos.phtml
Some Toxins are dangerous for animals and humans
How to measure changes?
Cell vs. system size
Plant, animal & human cells
Bakteria
MEMS, Microdluidic
Virus
Protine
DNA
Atoms
Transistor size
Structural sizes of
modern transistors
Mic
ro-E
lectr
onic
s
& M
EM
S
NE
MS
What is MEMS?
MEMS is an engineering discipline that studies the design and fabrication of micrometer to centimeter scale systems.
MEMS allow us to create artifical systems that are on the same scale and functionality as insects.
M icro E lectro M echanical S ystem
Scandia Lab
MEMS Example
Accelerometers, gyroscopes (airbag, Wii, EPS, …)
Flow sensors (Mass flow controller,
breath control, …)
Microoptics (Navigation Systems,
optical communication, …)
Microphones in cell phones Needles (Atomic force microsscope,
Medical applications,…)
And more!
Reference on request.
MEMS advantages
On-Chip (phosphate) in microfluidic package1.
Numerous benefits: - Reducing the sensor cost (batch fabrication) - Precise control of dimensions - higher processing speed, high accuracy - High abundance (multiple sensors of same and different kind on small foot
print) - reproducibility, - making the entire sensing system portable
1 Am Jang et al 2011 Meas. Sci. Technol. 22 032001
Challenges
Box
Sensor Sensor
Concept Challenges • Sensors
• Stiffness • Chemical
• Actuators • Media mixing • DEP
• Peripheries • Filter • Pumps
Science Translational Medicine 6 May 2015 Vol 7 Issue 286
Actuator: Media mixing RP Mixing nozzle
Herringbone mixer
Mixing of two fluorescent media
Biological: Cellular Stiffness
10 µm
Biogeochemistry1 Harmful Algal Blooms2 Stiffness change during chemical treatment
10 µm
Allow to study dynamics of cell state.
1 Wilken S. et al, Limnol. Oceanogr., 56(4), 2011, 1399-1410 2 B. Tesson, B. Charrier. Frontiers in Plant Science, V5, Article 471, 2014
Sensor: cell stiffness
Substrate
Frame (d ~ 0,7-0,9 dCell)
Glass
Cell
Stiffness ∝ ∆𝑡, 𝑑𝐹𝑟𝑎𝑚𝑒, 𝑑𝐶𝑒𝑙𝑙 0, Media
Hydrodynamic measurements
Easy to integrate in fluidic system
Micro-Squeezer
Si fabrication with permanent cover (bond)
Material and design development on the micro scale.
MSU Microfabrication Centre
Yeast : Cell differentiation
Compressed State
Non-Compressed State
Viable vs non-viable
S. Warnat, H. King, C. Forbrigger, T. Hubbard. JMM. 25,2,1420-25. JMM Highlight 2015
Reliability
System in seawater: • Corrosion of adhesion promotor • Electrical short between electrodes
Device not functional
Si Atomic Layer Deposition
TiO2 , Al2O3 – lamination stack
5min 80 µm
Not coated
S. Warnat, C. Forbrigger, T. Hubbard, T. Bertuch, G. Sundaram. JVAC A, 33 01A126, 2015
Summary
• Water sampling is important • High spatial and temporal density of multi parameter
field • MEMS allows ‘low-cost’ development
– … and more advantages
• Integration is challenging • Examples:
– Stiffness – Rupture Force – Reliability – (electrochemical sensor)
Acknowledgements
• Mechanical Engineering Dr. T. Hubbard, Dr. M. Kujath, Dr. D. Groulx
R. Schwartz, H. King, C. Forbrigger, B. Barazani
• Process Engineering and Food Science Dr. A. Macintosh, Dr. A. Donaldson
• Medicine Dr. A. Fine
S. Boyd
• Oceanography Dr. D. Wallace, Dr. H. MacIntyre
• Physics Dr. L. Kreplak, Dr. I. Hill
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