Biomedical Engineering Reference
In-Depth Information
Exercise A.7.2.
Describe three diferent methods for micropatterning gel-encapsulating
hydrogels.
Exercise A.7.3.
Encapsulating cells in a certain type of hydrogel is a common way to generate
3-D culture platforms. A microluidic laboratory is trying to reproduce this technique by mix-
ing C2C12 myoblasts with Matrigel and infuse the mixture into an open microtrench. We will
use confocal microscopy to observe a 1 mm × 1 mm ield of view with the ideal cell number of
500 in each
z
plane (depth of focus, ~10 μm). What is the concentration of the cell suspension in
the Matrigel we should use initially? he dimension of the trench is 5 mm in length, 500 μm in
width, and 200 μm in height.
A.8 Suggested Exercises for Chapter 8
Exercise A.8.1.
Discuss (a) what afects the signal/noise ratio and (b) biocompatibility risks in
(i) traditional EEG recordings, (ii) ECoG recordings, and (iii) recordings using microfabricated
intracortical multielectrodes produced by silicon micromachining. Note that you need to state
which material the electrode is made of (if diferent materials have been used in the literature,
you may choose one and stick to that one for the purposes of discussion).
Exercise A.8.2.
Name three diferent technologies for recording electrical signals from the
brain at diferent length scales. Describe, for each technology: (a) the dimensions and materials
used to make the electrodes, (b) the location/depth of recording, (c) the spatial resolution of the
recording (order of magnitude), (d) the typical duration (order of magnitude) of a recording, and
(e) the biocompatibility risks.
Exercise A.8.3.
Research the literature to ind published microfabrication processes for the
three main types of microneedles (one example each): in-plane microneedles, out-of-plane solid
microneedles, and out-of-plane hollow microneedles.
Exercise A.8.4.
Discuss challenges and possible solutions in the design of a microfabri-
cated cochlear implant with improved cell-electrode impedance and greater number of elec-
trodes compared with the Nucleus 24, one of the most prevailing and popular cochlear implants.
Exercise A.8.5 (Design Challenge).
Suppose you work for a consulting irm that assesses the
feasibility of engineering ideas before they actually go into research and development. A major
manufacturer of biomedical implants commissions you to assess whether it would be possible to
develop an implant for blind people that would directly stimulate the brain with the output of
a camera (rather than with retinal implants—the manufacturer has already tried that approach
and is not happy with it). hink of the assessment as the irst phase of the design, in which at
the beginning you are still open to any design and you have to narrow down the options of, for
example, materials of the device and biological principles of stimulation. he manufacturer is
not looking for a inal design—only an assessment of (a) the engineering challenges and (b) the
fundamental obstacles, which the manufacturer needs in order to determine the cost (of fabri-
cation, implantation procedure, etc.) and the targeted market (e.g., it may not work for all blind
people or it may only allow for partial vision).
Exercise A.8.6 (Design Challenge).
Propose the design of a retinal implant and discuss the
various challenges ahead, for example, signal processing, biocompatibility, power consumption,
surgery, ield of vision, and dynamic range.
A.9 Tips for a Good BioMEMS Exam
here is no substitute for serious study. Students oten make the mistake of invent-
ing things in exams. For example, when asked to come up with the microfabrication
process that leads to a given device, they might invent processes that have never been
