Teaching Materials - Introduction to BioMEMS - page 430

shown in class. Unless the purpose of the exercise is to show your ability to invent
new devices, it is a very risky strategy in an exam: most of them, I ind, have serious
laws. he processes taught in class were optimized ater considerable trial and error
and are only the tip of the iceberg of what very smart researchers tried out. If you are
an incoming student to the BioMEMS discipline, the way to succeed in designing
microfabrication processes is by studying (i.e., memorizing and understanding) lots
of them. Bottom line: if you invent in an exam or in a homework assignment, your
teacher will be able to tell.
Just answer the question(s). No student ever got credit for volunteering more infor-
mation than what was being asked. On the contrary, if you add something that is not
asked but is very wrong, it might inluence negatively on your grades. For the same
reason, do not write questions for the teacher or grader (“What protein will work bet-
ter?”)—you are the one being examined.
Some students use the concepts “chemisorption” and “physisorption” too liberally.
hese are processes that only apply to molecules on surfaces. herefore, it is incorrect
to say that “cells attach by chemisorption” (or by physisorption).
In photolithography, photoresist does not get “etched” (unless in the very particular
case in which it is attacked by a plasma). It gets developed or dissolved .
In exams, my students have repeatedly invented a type of photoresist that, much to
my regret, does not exist: one that can be spun and UV-patterned like most photore-
sists, and ater seeding cells on the photoresist pattern, it can be magically dissolved
without afecting cells. he closest that anyone has ever come to this goal is shown
in Figure 1.6 , in which Stefan Diez and coworkers were able to pattern proteins with
a photoresist whose water solubility changes with temperature. However, although
the process is compatible with proteins, there is no evidence that the polymer that is
crucial for the temperature phase transition, poly-NIPAM, is biocompatible enough
as to be compatible with cells. I am looking forward to the day when my students are
right!
A.10 Microluidics Outreach and Education
Fluids ofer endless opportunities to introduce scientiic concepts to kids in many areas that
are related to their everyday experiences, ranging from physics (swimming, rain formation)
and chemistry (cooking, explosions) to biology (bodily luids, marine life) and art (color mix-
ing). In our experience with children in science fairs, microluidics is equal to “luids with
a technology lavor” because it requires some component of fabrication or (if the device has
already been made for them) of observation of a new phenomenon, generally with a micro-
scope (which looks “cool”). Hands-on education (where students get to construct some device,
even if rudimentary) is most efective because the children actively think and learn while they
have fun. Two microluidic technologies have emerged as ideal for the classroom: paper and
Jell-O ( Figure A.7 ). hey are extremely low-cost, very safe, and simple to use and construct
(~5-10 minutes per device). If a CO 2 lase is available, more sophisticated microluidic devices
can be produced by laser cutting of plastic laminates in a few minutes (see Section 1.4.4),
which allows for teaching complex phenomena such as droplet formation and chaotic mixing
(e.g., for advanced undergradute laboratories).