Cell Adhesion

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Cell Adhesion

• Matt Tanke
• Will Howerton
• Stewart Bewley
• Jeff Mills

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Cell Adhesion Measurement Device

• Cell sits between two plates
• One plate fixed, one plate attached to linear
  spring
• Actuator pulls spring into tension

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Adhesion of Cell

• Cell will have a smooth outer membrane or
  flagellum
• Both exhibit non-linear cell/plate separation

Flagellum
Smooth Membrane
http//fig.cox.miami.edu/Faculty/Dana/105F00_4.htm
l
http//library.thinkquest.org/16985/cellmain.htm
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Adhesion of Cell
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Current Design Optical Tweezers

• Nm displacement
• pN force
• Glass bead dependent

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Scratch Drive

• µN forces
• 500 µm displacement
• Difficult to model

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Nano-tractor

• 40 nm step size
• Moves at 3 mm/s
• Stalls when 2.5 mN max tangential force is reached

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How it works
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Accuracy
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SUMMiT V Process Flow

• Conformal Deposition
• Planar Depostion
• Dry Etch
• Wet Etch
• Release Etch

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Diagram and Variables
ks
kc
D1
D2
P2
P1

• kc is the spring constant of the cell
• ks is the spring constant of the spring

• D2 is controlled by nano-tractor
• P2 is the force needed for nano-tractor

• P1 is the force needed to pull the cell
• D1 is the displacement of the cell

• 6 variables D2, P2, ks, D1, P1, kc
• 2 equations can be derived
• P1 D1(kc ks) D2ks
• P2 ks(D2 D1)

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Assumptions
ks
kc
D1
D2
P2
P1

• Finding kc
• Assumptions
• Cell is a cylinder
• Diameter equals length
• Diameter roughly 10-50 um
• Calculation
• kc Epid/4
• kc .0076-.0393 N/m

• P2 is not needed
• Assumptions need to be made for other variables
  in order to find values for ks

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Finding ks
ks
kc
D1
D2
P2
P1

• Verification
• Find increment for D2 that works for range
• Must be greater than 40 nm
• Selected 250 nm
• Check if increment will be detectable

• Assumptions
• P1 1-100 nN
• D2 11 um ls D1
• Due to limit of optical measuring tool
• Assume ls 8 um
• Made spreadsheet
• ks 0.0246 N/m

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Overview of Range
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Spring Dimensions

• 2 double cantilever beams
• ks Et(w/l)3
• w 2.25 um
• l 785 um
• T 7 um

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Results
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Thank You

• Questions?