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MEMS- MicroElectroMechanical Systems Batch Fabrication Processes Cell Traps High-throughput experimentation Complex biochemical analysis Single cell analysis Reagent conservation Quick environmental changes
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Optimization of T-Cell Trapping in a Microfluidic Device
Group #19Jeff Chamberlain
Matt HoustonEric Kim
Advisors: Dr. John Wikswo, Dr. Kevin Seale
MEMS- MicroElectroMechanical Systems
• Batch Fabrication Processes
• Cell Traps– High-throughput
experimentation– Complex biochemical
analysis– Single cell analysis– Reagent
conservation– Quick environmental
changes
Our Project
• Maximize trap efficiency by improving upon current trap designs.
– Maximize total number of cells trapped or minimize total number of cells wasted
– Maximize number of traps with 1 cell / trap
Trap Efficiency
Success
– Define a trap type that optimizes each trapping efficiency definition.
For example:
SolidWorks® Rendering of a Single Well
Picture of Well Array• Square or rectangular
shaped well of any depth
• Thousands of mirrored wells in one etching
• Front Surface Mirrors with high reflectivity
• Nearly orthogonal views of specimen
200 um200 um
Background & MotivationThree Dimensional Image Information May
Be Important for Biological Studies
• Chemotaxis• Developmental Biology• Cellular Division• Pinocytic Loading • Volumetric Measurements
Our System is Constructed From Silicon Wafer <100>
Methods: FabricationSilicon Wafer Silicon Wafer <100><100>Grow SiOGrow SiO22
Spin Coat Mask Spin Coat Mask LayerLayerPattern with Pattern with PhotolithographyPhotolithography Etch with HFEtch with HF
Remove Remove PhotoresistPhotoresistEtch with KOHEtch with KOH
Coat with Platinum Coat with Platinum or Aluminumor Aluminum
Cutaway ViewCutaway View
Micromirror Well DimensionsLIGHT RAY
Well Dimension Requirements• Bottom should be 40% larger than the cell diameter
• Reflected light ray should be above the top of the cell
19.4O
hd
Equations• Minimum Etch Depth
h = d + w/2 * tan(19.4o)
• Well Bottom Size
b = w – 2*h / tan(54.7o)
w
b
h - d
54.7O
54.7O
h
h / tan(54.7o)
Micromirror Well DimensionsLIGHT RAY
19.4O
hd
w
b
h - d
54.7O
54.7O
h
h / tan(54.7o)
Cell Type Cell Diameter, d (um) Minimum Required Depth, h (um)
Outside Dimensions, w (um)
T-cells 5.5 8.8 21Jurkats 10 16.6 37.5Dendritic 15 25 57Dicti 10 (height, d = 20-30) 16.6 37.5
Coupling Microfluidics With the Pyramidal Wells
Si Wafer
Cross Section of One Well
PDMS
Flow
Flow
PDMSGlass
Device Layout
Traps & Device for Primary T-cells (d = 5.5µm)
Jurkat Cells in Traps
Defining Success
• Trapping efficiency implies two things:– Highest % of Traps Filled– Highest % of Traps with 1 Cell
• Goals:– % of Traps Filled above 90%– % of Traps with 1 Cell above 10%– Identify strengths of individual traps for future
use
Data Analysis
Mean Percentages for Trap Types
0
20
40
60
80
100
120
SFLD TSLD SSLD TSHD TFHD
Perc
ent
Percent Traps Filled
Percent Traps with 1 Cell
Data Analysis
Low Density Vs High Density
0
20
40
60
80
100
120
140
160
180
200
% Traps Filled % Traps with 1 Cell
Perc
ent
Low Density
High Density
Data Analysis
Front to Back
0
20
40
60
80
100
120
0 20 40 60 80 100 120
Column #
Perc
ent
% Traps Filled% Traps with 1 Cell
Successes and Future Goals
• Goals Achieved:– % of Traps Filled above 90% with all but
SFLD– % of Traps with 1 Cell above 10% with all but
TSLD• Future Goals:
– Test new trap designs with observed characteristics
– Test “front to back” hypothesis
Future Plans
• Create and test micromirror coupled devices– Micromirror synthesis beginning this week– Masks expected within the next two weeks
• Develop fluid flow profiles for traps and wells for further and future study and optimization