1. Optimization of T-Cell Trapping in a Microfluidic Device Group #19
Jeff Chamberlain
Matt Houston
Eric Kim
Advisors: Dr. John Wikswo, Dr. Kevin Seale

2. MEMS- MicroElectroMechanical Systems
Batch Fabrication Processes
Cell Traps
High-throughput experimentation
Complex biochemical analysis
Single cell analysis
Reagent conservation
Quick environmental changes

3. Our Project
Maximize trap efficiency by improving upon current trap designs.

4. Trap Efficiency
Maximize total number of cells trapped or minimize total number of cells wasted
Maximize number of traps with 1 cell / trap

5. Success
Define a trap type that optimizes each trapping efficiency definition.
For example:

6. SolidWorks® Rendering of a Single Well
Four images are seen here, a fifth is hidden behind the real object
Important to notice that the overall size of the well and the size and angle of the mirrors affect the simultaneity of the images.

7. 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
Shown here is a pattern of a few thousand wells next to a regular sized paper clip, before metal coating
Here is a microscope image of twenty 200 wells that are 200 microns at the top and about 100 microns at the bottom – the mirrors appear dark.
These wells are about 70 microns deep, but they can be made any size and depth constrained only by the geometry defined by the etch angle of 35.3 degrees.
200 um

8. Background & Motivation
Three Dimensional Image Information May Be Important for Biological Studies
Chemotaxis
Developmental Biology
Cellular Division
Pinocytic Loading
Volumetric Measurements
Immune synapse and cytoskeletal trunk from the membrane to the nucleus are orthogonal
Rearrangement of the cytoskeleton during chemotaxis occurs in three dimensions
Embryo development is an orchestrated movement of cells in all three dimensions simultaneously
My research
Jake’s research

9. Our System is Constructed From Silicon Wafer <100>
We fabricate the wells on the <100> plane of silicon wafers
Shown here are 2” 3” and 5” wafers, all of which are very flat, polished single crystals of silicon
These are commonly available because of their use in semiconducter manufacturer

10. Methods: Fabrication Silicon Wafer <100> Grow SiO2
Spin Coat Mask Layer
Pattern with Photolithography
Etch with HF
Walk through fabrication
1) The silicon etches anisotropically, so that the side walls of the wells are at very specific angles to the <100> plane.
Remove Photoresist
Etch with KOH
Cutaway View
Coat with Platinum or Aluminum

11. Micromirror Well Dimensions
LIGHT RAY
19.4O
54.7O w
h - d h h d
54.7O
h / tan(54.7o) b
Well Dimension Requirements
Bottom should be 40% larger than the cell diameter
Reflected light ray should be above the top of the cell
Equations
Minimum Etch Depth
h = d + w/2 * tan(19.4o)
Well Bottom Size
b = w – 2*h / tan(54.7o)

12. Micromirror Well Dimensions
LIGHT RAY
19.4O
54.7O w
h - d h h d
54.7O
h / tan(54.7o) b
Cell Type
Cell Diameter, d (um)
Minimum Required Depth, h (um)
Outside Dimensions, w (um)
T-cells
5.5
8.8 21
Jurkats 10
16.6
37.5
Dendritic 15 25 57
Dicti
10 (height, d = 20-30)

13. Coupling Microfluidics With the Pyramidal Wells
Flow
PDMS
Glass
PDMS
Flow
Si Wafer
Cross Section of One Well

14. Device Layout Jurkat Cells in Traps
Traps & Device for Primary T-cells (d = 5.5µm)

15. Defining Success Trapping efficiency implies two things: Goals:
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

16. Data Analysis

17. Data Analysis

18. Data Analysis

19. 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

20. 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