NANO203 2025 Homework #2
Instructions: You may use the literature and library resources but not Chegg or similar sites. You may not work with other classmates. Please upload a Word file or PDF to Canvas. 120 total points.
Due: Due at 5:00 PM on Friday March 14. I will post the key shortly after that so you can use it to study for the final.
1. We discussed the Hall-Petch effect in our discussion of nanoarchitectures: There is a grain size of ~30 – 100 nm where the material is strongest. Is the Hall-Petch effect discussing single crystalline systems or polycrystalline systems? Why do grain sizes < 30 nm have decreased strength? Why do grain sizes greater than ~ 100 nm have decreased strength? (15)
2. Layer-by-layer assembly using spinning usually offers films that are smooth and stratified. Why would you ever want to use an immersive process? Also, name and describe three ways that people characterize systems created by layer-by-layer assembly. (14)
3. Which two forces underly the adhesion properties of natural gecko setae? Which one predominates? (4)
4. We discussed three printing-based approaches to assembly: nanoimprint lithography, transfer printing, and inkjet printing (6)
a. Rank them in terms of costs: most expensive first to cheapest.
b. Rank them in terms of spatial resolution: best (smallest) resolution to worst.
5. What’s the difference between a z statistic and a t statistic on Student’s t-table? (6)
6. Explain why nanoparticle size is so critical in dielectrophoresis-based self-assembly. Name other knobs you have to increase the strength of dipole/dipole interactions in dielectrophoresis-based assembly? Which direction would you turn them to increase the strength? (15)
7. You have developed a couple new methods to make coatings on a substrate. You measure the new coating thickness multiple times and note that it is 2.80 nm, which is roughly 13% higher than the old method (2.48 nm).
a. What is the 99% confidence interval of these two data sets? What about the 90% confidence interval? Which interval is wider? Does that make sense? Note: people use both t-statistic and z-statistic here; please use the z statistic for grading consistency. Do this by hand and show all work. (15)
b. How much confidence do you have that method 2 makes thicker coatings than method 1? Do this by hand and show all work. Then do this with excel. Compare methods. (15)
c. The 3.50 nm trial seems to be an outlier. Can you reject this data point? If so, how much confidence do you have in doing this? (10)