Force Spectroscopy

Question 1

What is the basic principles of Force Spectroscopy?

Answer 1

1. Cantilever moves in vertical direction (z-axis).
2. Cantilever deflection recorded, as a function of displacement versus displacement curve.
3. Converted to force-distance curve after Hooke’s Law

Question 2

What is Hooke’s law of elasticity?

Answer 2

F = - k . Δx
F: force
k: spring constant
Δx: length of deflection

Question 3

What does the force-distance curve depend on?

Answer 3

1. Tip
2. Sample
3. Medium composition

Question 4

How does Force Spectroscopy work?

Answer 4

1. Cantilever approaches surface
2. Attractive force exceeds value of spring constant
3. tip deflects and jumps in contact with surface
4. Tip presses on sample, deflection and repulsive force increase
5. Tip begins retracts from sample
6. Upward movement overcomes tip-sample interacting force
7. Tip released away from sample

Question 5

What effect does gelatin have on YM?

Answer 5

YM increases with gelatin concentration.
YM from slope.