Optimization of T-Cell Trapping in a Microfluidic Device Group #19

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