Cell Adhesion

Matt TankeWill HowertonStewart BewleyJeff Mills

Cell Adhesion Measurement Device

Cell sits between two plates

One plate fixed, one plate attached to linear spring

Actuator pulls spring into tension

Adhesion of Cell

Cell will have a smooth outer membrane or flagellum

Both exhibit non-linear cell/plate separation

Flagellum

Smooth Membrane

http://library.thinkquest.org/16985/cellmain.htm

http://fig.cox.miami.edu/Faculty/Dana/105F00_4.html

Adhesion of Cell

Current Design: Optical Tweezers

Nm displacement

pN force

Glass bead dependent

Scratch Drive

μN forces

500 μm displacement

Difficult to model

Nano-tractor

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

How it works

Accuracy

SUMMiT V Process Flow

Conformal Deposition

Planar Depostion

Dry Etch

Wet Etch

Release Etch

Diagram and Variables

6 variables: D2, P2, ks, D1, P1, kc

2 equations can be derived: P1 = D1*(kc + ks) – D2*ks

P2 = ks*(D2 – D1)

D2

P2

ks kc

D1

P1

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

kc is the spring constant of the cell

ks is the spring constant of the spring

Assumptions

P2 is not needed

Assumptions need to be made for other variables in order to find values for k’s

D2

P2

ks kc

D1

P1

Finding kc

Assumptions Cell is a cylinder Diameter equals length Diameter roughly 10-50 um

Calculation kc = E*pi*d/4 kc = .0076-.0393 N/m

Finding ks

D2

P2

ks kc

D1

P1

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

Verification Find increment for D2 that works for range

Must be greater than 40 nm Selected 250 nm

Check if increment will be detectable

Overview of Range

Case Ks (N/m)

Kc (N/m)

P1 (nN)

D1 (um)

D2 (um)

# of Increments

Most Elastic Cell

.0246 .0076 100 22.0 25.0 100

Least Elastic Cell

.0246 .0393 1 1.74 4.74 20

Spring Dimensions

2 double cantilever beams

ks = E*t*(w/l)3

w = 2.25 um l = 785 um T = 7 um

Results

Thank You

Questions?