Biomedical Engineering Reference
In-Depth Information
Exercise A.1.8.
If a wafer is spun with the photoresist SU-8 (speciically, SU8 2035) at 2000
rpm for 30 seconds, what will be the ilm thickness? What if it is spun for 2 minutes at 2000 rpm?
(Please check the data sheet available at http://www.microchem.com/Prod-SU82000.htm). What
speed would you have to spin SU-8 2050 to achieve the same thickness?
Exercise A.1.9.
A photolithography machine with known dose of UV light (6.5 mJ/cm
2
per
second) is used to expose a silicon wafer that has been coated with 75-μm-thick SU-8 photo-
resist. he SU-8 data sheet suggests that the exposure energy should be 150 to 215 mJ/cm
2
for a
thickness of 45 to 80 μm of SU-8 (please check the data sheet from www.microchem.com). How
many seconds should the wafer be exposed to properly cross-link 75-μm-thick SU-8?
(a) 20-26 seconds
(b) 28-34 seconds
(c) 37-43 seconds
A.2 Suggested Exercises for Chapter 2
Exercise A.2.1.
Describe three diferent methods for creating protein micropatterns. Ater you
have described all three methods step by step, describe four diferent applications of protein pat-
terning. For each application, choose which method you think would be the best of the three and
explain why you have chosen that one (and not the other two).
Exercise A.2.2.
Describe (using cross-sectional schematics) two alternative microfabrication
processes that yield the cellular microstructures seen in
Figure A.3
. he inset shows a large-
scale view to give an idea of the pattern. Assume that the substrate is polystyrene for one of the
processes and glass for the other alternative.
Exercise A.2.3.
Draw, in cross-sectional schematics, two diferent step-by-step microfabrica-
tion processes (one using only photolithography, the other using sot lithography) for producing
the cellular microarray in
Figure A.4
on a lat surface. Please be speciic when explaining how
the materials/molecules are immobilized on the surface—that is, is it by physisorption or by
chemisorption, and if the latter, make sure that the chemical reaction that you are proposing is
not vague or ambiguous.
Exercise A.2.4.
A suspension of cells (luorescently labeled blue, in serum-free medium) is
added onto a surface that contains a micropattern of many islands just like the luorescence
micrograph shown in
Figure A.5a
. he X, Y, and Z letters denote surface coatings or grats
(i.e., they can be physisorbed or chemisorbed; you will have to igure it out in this exercise).
Albumin
Collagen
100 µm
Hepatocytes
FIGURE A.3
Cellular.micropattern.
