Schuab 4:00
R18
BIODEGRADABLE CIRCUITS DEVELOPED FOR TEMPORARY MEDICAL
DEVICES
Bodhisatwa Biswas (bob11@pitt.edu)
device, made of disposable circuits, would be implanted at
the site of surgery and sutured up. Here, the device would
serve its antibacterial purpose for a few weeks, and
eventually dissolve [4].
Degradable circuits will create many medical opportunities
for us, even beyond facilitating post-surgical recovery. We
have the potential to create devices that can me implanted to
deliver drugs to certain parts in the body [4]. Jeffrey
Borenstein, a bio engineer at Draper Laboratory, even
speculates the use of disposable circuits to monitor soldiers’
health on the battlefield [1].
BREAKING FROM THE CURRENT TREND
IN CIRCUITS
Presently, the popular goal in computer electronics is to
manufacture products that are durable and can withstand
deterioration. Over the last few years, computer circuits
have become more stable and longer lasting [1]. Engineers
from Tufts University and the University of Illinois have
collaborated to show that the opposite goal is also a worthy
investment to the medical field [2]. They have been able to
create simple electronic devices and circuits out of
biodegradable components like silicon and magnesium.
Normally, devices that are implanted into a patient during
surgery must be surgically removed once it has served its
purpose. Otherwise, the patient is burdened with having the
machine stuck inside forever. With the development of
biodegradable circuits, medical devices may be implanted in
a patient, and harmlessly deteriorate after a set time period
[3]. By implementing biodegradable circuits, mechanical
implants can become a more effective method for medical
treatment. Likewise, we will discuss the ethical reasons why
biodegradable devices are worth investing time and money
into developing for the public market.
MANUFACTURING A BIODEGRADABLE
CIRCUIT
Implanting Temporary Sensors
“Many of the devices we implant into patients are only
needed temporarily,” says Dr. Marvin J Slepian, a
cardiologist and professor of medicine at the University of
Arizona [2]. The current limitations in temporary medical
devices make many surgical procedures riskier than
necessary. He further elaborates by using artificial heart
transplant as an example. After the operation, doctors are
blind to the status of the implant in the patient’s chest. By
placing biodegradable sensors alongside the artificial heart
during the implant, we could track the blood pressure and
heartbeat of the patient. This would be critical data in the
first two weeks post-implant, when the new heart is most
likely to malfunction. These sensors would be invaluable in
monitoring any organ such as the kidney or the lungs for a
set amount of time, be it days, weeks, or months [2].
FIGURE. 1. Transient chip created using silicon,
magnesium, magnesium oxide, silicon dioxide, and silk [5]
FIGURE. 2. Transient chip degrading after 5 and 10 minutes
dissolving in water [5]
The biodegradable circuit, coined the “transient circuit,” is
the result of the joint effort of bioengineers at Tufts
University who focus on the medical application of silk and
electrical engineers at the University of Illinois who
specialize in very small silicon-based electronics [2]. In
order for the transient chip to be truly degradable, it had to
be built using novel components that were both
Preventing Surgical Infections
Another use of disposable circuits currently being tested
seeks to prevent infections to surgical sites. The leading
cause of post-surgical revisits is infection [1]. A new
medical device is being developed that creates heat and
effectively kills all bacteria in the surrounding tissue. This
University of Pittsburgh, Swanson School of Engineering
October, 30, 2012
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Bodhisatwa Biswas
biodegradable and harmless for the human body. The
transient circuit is built upon a silicon base serving as a
semiconductor [5]. Silicon naturally degrades (forming
silicon tetraoxide) in bio-fluids at approximately 1nm per
day. This rate is negligible in normal sized chips, but
becomes relevant when the silicon base is close to 100nm
thick. In fact, the transient circuit in Fig. 1 was produced
using <1 microgram of silicon, which takes approximately
30 microliters of bio-fluid to dissolve [5]. Furthermore, the
circuit pathways themselves are made of magnesium, while
the dielectrics are made of magnesium oxide and silicon
dioxide. Magnesium is a compound that is naturally found
in our bodies, and biodegrades quickly with no harmful
effects [5]. The circuit is designed to degrade after
absorbing a certain amount of water, but may also be
signaled to degrade through pH and temperature change [4].
A new substance is now needed to time the moment when
the circuit starts degrading. To combat this problem, the
researchers at the University of Illinois decided to
experiment with silk. They extracted it from silkworm
cocoons, boiled it, and created a biodegradable compound
that coats the circuit [1]. Silk is a more attractive compound
than other synthetic polymers because of its “ability to tailor
the dissolution, and/or biodegradation rates from hours to
years, the formation of non-inflammatory amino acid
degradation products, and the option to prepare the materials
at ambient conditions to preserve sensitive electronic
functions” [6]. Furthermore, silk has proved to be medically
safe because of its extensive use as surgical suture for
decades [4]. Once the circuit is properly coated, the
laminating layer of silk slowly degrades and serves as a
timer for when the circuit makes contact with the
surrounding bio-fluid. Depending on the number of silk
layers, this can range from “under a minute to months” [6].
procedures. 58 out of the 64 (>90%) pixels functioned
correctly [6]. The only problem faced while developing the
camera was finding a source for energy. As of now, the best
solution is the use of silicon-based solar cells, which are
non-degradable due to their relatively mammoth size (~3mm
thick) [6]. Further development in transient chips may
allow us to implant temporary cameras that monitor the
human body in ways previously not possible.
ETHICS OF DEVELOPING
BIODEGRADABLE MEDICAL DEVICES
Transient machines could easily evolve from animal to
human testing, since biodegradability of these compounds is
seemingly identical between our species. However, we must
be prudent and patient in developing any medical equipment
that will directly affect the health of human patients. As
stated in the first canon of the National Society of
Professional Engineers code of ethics, the welfare of the
public is top priority [7].
The adverse effects of
biodegradable chips are not fully known, especially not in
the long-term. This means that a lengthy testing procedure
is required for these newly invented devices.
The
Biomedical Engineering Society possesses its own code of
ethics that specifically deals with the testing and
development of medical equipment. Biomedical engineers
must be aware of a myriad of guidelines as they practice in
their field. They must, “comply fully with legal, ethical,
institutional, governmental, and other applicable research
guidelines” [8]. Likewise, they must respect the rights of
their human and animal subjects. This strict guideline for
medical advancement creates an arduous, but necessary
process. It ensures that whatever medical equipment or
procedure is open to the public, has been certified to be
effective and safe. Though the public application of
biodegradable medical devices may be years in the future,
we can be sure it won’t be a haphazard attempt. It seems
that research in biomedical engineering is slower than most
other engineering fields, but it is thoroughly rewarding in the
fact that you directly help benefit the lives of countless
humans.
The NSPE also mandates that engineers strive to serve the
public interest. More specifically, and with relevance to the
development of biodegradable devices, the NSPE
encourages “sustainable development in order to protect the
environment for future generations” [7]. Currently, the
healthcare industry is the second largest producer of waste in
the United States, second only to the food industry [9].
Traditional medical devices that are no longer needed are
discarded as bio-hazardous waste. With the development of
biodegradable medical devices, we may create a more
sustainable and environmentally friendly healthcare system.
The use of biodegradable materials like silicon for creating
medical devices ties into another ethical clause of the
BMES: biomedical engineers must account for the
TESTING FUNCTIONALITY AND
PROPERTIES OF TRANSIENT CIRCUITS
In order to analyze the effectiveness of these newly
developed transient circuits, their biodegradability as well as
functionality need to be tested.
Researchers at the
University of Arizona have already started implanting these
circuits in mice to gauge how well they perform. Chips that
generate heat to prevent infection in surgical wounds were
wrapped in silk layers and inserted under the dermis of mice.
After three weeks, the sutures were reopened to reveal that
only faint residues of the chip were still left behind [6].
Furthermore, there was no sign of inflammation at the site of
implantation [6]. This signifies that the degradation of the
chip caused no adverse effect to the surrounding tissue.
Next, the researchers at the University of Arizona decided to
test how well the transient circuits could actually function. A
sixty-four pixel camera was built using transient circuits
meant to capture images during and post surgical
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Bodhisatwa Biswas
“consequences of their work in regard to cost, availability,
and delivery of health care” [7]. Silicon is an abundant
material, and much cheaper to manufacture with than more
robust counterparts. Biodegradable devices may be cheaper
to
manufacture
than
non-biodegradable
devices.
Additionally, biodegradable devices make secondary
procedures to “phish out” temporary devices obsolete.
Overall, the implementation of these new devices can drive
down the cost of healthcare for hospitals and patients.
very effective method in retaining them in the field as well
as developing them as engineers. This may have been the
motivation for assigning this paper, but it overlooks a key
fault. During my time writing this paper, I realized I have
been spending most of my time formulating a persuasive
essay. I agree that an engineer should be well rounded in
scientific topics as well as rhetoric, but that is simply not the
top priority, especially in the freshman year. Instead, an
ideal freshman engineering assignment is one where we are
given a real-world engineering problem, have to analyze it
through experiments and real analytical data, and then must
formulate a conclusion or solution by discussing it with
peers. In fact, this exact approach to freshman engineering
was implemented by The South Dakota School of Mines and
Technology in 1997 [10]. They started a two credit
engineering class that dealt with 2-3 engineering problems a
semester. This approach to the freshman curriculum was met
with overwhelming positive feedback from both professors
and alumni groups from local engineering companies. This
method of exposing students to real-world engineering
topics had the added benefits of motivating critical thinking,
integrating technical skills with math and sciences, and
finally, forging communication skills and teamwork [10].
The writing assignment was sufficient in garnering my
interest in bioengineering topics and evaluating the ethics
that go along with being an engineer, but it didn’t have the
benefits found in the curriculum invented by The South
Dakota School of Mines and Technology.
DEGRADABLE MACHINES AND FUTURE
OPPORTUNITIES
It is hard to refute the notion that biodegradable machines
are the future of temporary medical devices. Right now,
there is a great need for supplemental devices that can
monitor body function for a set period of time. After
surgery, doctors are blind to the internal physiology of the
patient [2]. With the development of temporary sensors,
post-surgery recuperation can be accurately monitored
without the need to remove the devices at a later time. A
crucial development to open-heart surgery would be the
implantation of a temporary pacemaker that regulates
heartbeat in the weeks following the operation [2]. The
implementation of heat to prevent bacterial infection is also
an ingenious use of temporary supplemental machines. The
number of postsurgical infection cases would plummet if
these antibacterial machines were widely used [2].
As of now, transient circuits are just in the preliminary
phases of testing. The machines are simple, but there is no
indication that they can’t be as complex as ones made with
larger, more robust components. With continued research, it
will be possible to manipulate even thinner pieces of silicon
to create complex circuits [3]. Further advancements in
technology, as well as further testing is necessary. More
experiments on animals, with higher-functioning transient
machines will certainly spark interest in the medical
community [3], [4]. Though research may be slow, it makes
sense ethically to devote time and energy to developing
these machines if it means bettering countless lives for
cheaper and reducing medical waste in the ecosystem.
REFERENCES
[1] C. Y. Johnson. (2012). “Short-lived Circuits Promise
Range of New Uses.” Boston Globe. (Online Blog)
http://articles.boston.com/2012-1001/business/34177808_1_silk-electronic-devices-researchers
[2] L. Ahlberg, D. Svolte. (2012). “Electronics That Vanish
in the Body.” UANews. (Online Blog)
http://uanews.org/story/electronics-vanish-body
[3] C. Arnaud. (2012). “Implantable Silicon Devices
Designed To Disappear.” Chemical and Engineering News.
(Online Article)
http://cen.acs.org/articles/90/i40/Implantable-SiliconDevices-Designed-Disappear.html
[4] R. Ehrenberg. (2012). “Degradable Devices Vanish After
Use.” Science News. (Online Article)
http://www.sciencenews.org/view/generic/id/345428/title/De
gradable_devices_vanish_after_use
[5] S. Hwang et al. (2012). “A Physically Transient Form of
Silicon Electron.” Science 337, 1640. (Online Article), DOI:
10.1126/science.1226325
[6] D. Kim, Y. Kim, J. Amsden, B, Panilaitis, D. Kaplan.
(2009). “Silicon Electronics on Silk as a Path to
Bioresorbable, Implantable Devices.” American Institute of
Physics. (Online article), doi: 10.1063/1.3238552
EDUCATIONAL VALUE OF THIS PAPER
The role of this paper has been to encourage me, the student,
to research an engineering topic that interested me. I had to
determine the pros and cons of said topic and form my own
conclusion as to what stance is right. Then, I had to research
the ethical codes of professional engineers and relate them o
my topic and the stance I took relating to it. In my opinion,
this writing assignment did have value, and did spark my
interest in a niche topic regarding transient medical devices,
but our engineering curriculum could have used the time for
more valuable assignments. It has been shown that exposing
freshman engineers to real-world engineering problems is a
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Bodhisatwa Biswas
[7] Unknown author. “NSPE Code of Ethics for Engineers.”
NSPE. 2012. (Online Article)
http://www.nspe.org/Ethics/CodeofEthics/index.html
[8] Unknown author. “Biomedical Engineering Code of
Ethics.” BMES. 2012. (Online Article)
http://www.bmes.org/aws/BMES/pt/sp/ethics
[9] A. Atkinson. (2011). “Reprocessed Medical Devices:
Saving Money and Reducing Waste.” Scrubs+Suits. (Online
Article)
http://scrubsandsuits.com/reprocessed-medical-devicessaving-money-and-reducing-waste/
[10] J. Kellar. (2000). “A Problem Based Learning
Approach For Freshman Engineering.” CiteSeer. (Online
Article)
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.19.
7481
ACKNOWLEDGEMENTS
The topic of this paper was chosen because of my interest in
bioengineering. This interest was sparked by my parents
Chandra and Chhanda Biswas, both of whom are
researchers. My excellent chemistry teacher in 12th grade
also bolstered my interest in medical research.
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