The Atomic Force Microscope

1. The Atomic Force Microscope

2. The Braille Game! Can you feel the surface and identify the features?

4. What is nano? 10-9 meters (one billionth of a meter) Objects between 1-100 nm 1 mm = 1000 μm μm, micrometer, micron 1 μm = 1000 nm

5. Individual fibers are 18 ± 1 μmHow many mm?How many nm? Blue mouse pad 400X

6. How can we visualize or “see” such small items?

7. The first AFM Invented and built in 1985 by Calvin F. Quate , Gerd Binnig, and Christoph Gerber. This is the first Atomic Force Microscope. The AFM works by ‘touching’ objects with the probe and reading the surface rather than looking at them. sciencemuseum.org.uk

9. What is the AFM? An analog!

10. AFM Chip, Cantilever + Tip holder http://www.tedpella.com/probes_html/budgetsensors.htm 7/13/11

11. AFM cantilever and AFM tips The tip is roughly 20 µm long, the cantilever is 450 µm in length and 20-50 µm wide, and the thickness is usually 3-4 µm thick. http://www.tedpella.com/probes_html/budgetsensors.htm 7/13/11 www.veeco.com, 7/13/11

12. Basic operation of the AFM AFMs monitors the forces of attraction and repulsion between a tip and a sample surface The tip is attached to a cantilever which moves up and down in response to forces of attraction or repulsion with the sample surface Movement of the cantilever is detected by a laser and photodetector

13. AFM Schematic Let’s talk about contact mode Actuator contains a piezoelectic crystal that expands and contacts as a voltage is applied across its crystal surfaces…a few hundred volts can be applied to move the scanner tens of microns Nanosurf AFM acquires an image by scanning a sharp probe across the surface

14. Two common AFM system designs Sample movesrelative to the tip Tip moves relative to the sample

15. The powerful, versatile AFM Resolutions: X and Y 2 -10 nm Z 0.05 nm Microstructure of solids: CD, glass beads, circuits Biological samples: skin cross section, viruses, bacteria, blood, DNA and RNA ~30 um scan http://www.nanotech-now.com/Art_Gallery/antonio-siber.htm July 13, 2011

16. Feedback loop and gains To make a topographical image in contact mode, a feedback loop is implemented to keep the deflection of the cantilever constant as the Z height changes to bumps on the surface. The topographical image is created by recording the Z output as a function of x and y position.

17. Borrowed image to illustrate scanning

18. Limitations on the tip size

19. Double effect – tip artifact Salt crystals imbedded in a polymer matrix borrowed image

20. Gains control In which image are the gains too high, too low, or just about right? borrowed image

21. Thank you!

22. AFM Image Library

23. Dan Witt’s AFM images – calibration gridMishawaka High School Teacher, July 2010

24. Silicon calibration grid, vgoss – AFM

25. Ram memory chip, vgoss - AFM

26. Ram memory chip, vgoss - AFM

27. CD, vgoss - AFM

28. staphylococcus aureus bacteria on glass substrate, vgoss -AFM

29. staphylococcus aureus bacteria, on glass substrate, vgoss - AFM

30. 2 nM DNA origami in air, vgoss -AFM

31. 2 nm DNA origami in liquid, vgoss - AFM