Memo
Date: January 27 2015
To:
Inst. Trott & GTA Mohini
From: Joshua Epperson and Group R-Luisa Parish, Brook Ott, and Ben Weisman
Subject: Lab Introduction to Lab-On-A-Chip
Introduction
Lab 1 consisted of analyzing and qualifying a generic lab-on-a-chip design that the team will be
creating throughout the course of the semester. Experimenting with the chip included testing the
channels, the overall design—use of detection wells and the capillary check valves. Testing of the wells,
valves, and channels also allowed the team to examine the performance of the chip and understand the
importance of set procedures and equipment—dirt removal, sterile instruments, and so forth. This
memo examines the observations made while examining the chip, answers specific questions pertaining
to the functionality of nanotechnology in the future, and includes an initial chip design sketch. Without
the aid of Luisa Parish, Brook Ott, and Ben Weisman this lab would not have been possible.
Results
The team began the lab by cleaning the PDMS chip. While cleaning they took into account the general
layout of the staging wells as well as the placement of the holes on the cover of the chip. There were 5
staging wells, they were numbered counter-clockwise with 1 being the well closest to the team label.
When placing the two pieces together the team noticed that the holes above the staging wells were
slightly off, they were unsure if the performance of the chip would be compromised so each well was
tested several times moving the hole around to find the best position. When testing each staging well it
was discovered that wells 2 and 3 worked the best, filling up the staging well as well as allowing the fluid
to proceed through the channels to the detection and waste wells. Behind these in performance was
Well 4—there were an equal number of times where the well would overflow as it would perform as
expected. Meanwhile, wells 1 and 5 performed the worst relatively, overflowing the wells before
reaching the check valve. No matter how much pressure was placed around the wells or the wells were
cleaned they still managed to overflow, therefore there was another issue inhibiting the performance of
the well.
For the majority of trials, when the well and channels worked as expected the check valve worked in
pausing the motion of the fluid for a short period of time. All of the staging wells had check valves a
short distance from the staging well along the channel. For the staging wells that worked well—2, 3,
and 4—the capillary check valves performed as expected. After several trials with each well the team
examined the chip using a 5x magnifying glass. The team noticed that there were lines going through
staging wells 2 and 3 that appeared to be scratches. The same was noticed with the waste well. It was
theorized that the slits helped with the performance of those respective wells, however, a more
thorough investigation would be needed before a conclusion could be arrived at. Also, using the
magnifier it was noticed that there was slight dirt debris in well 2. While this should have hindered the
performance of the well, such was not the case.
Discussion
During the lab the team took into account the exact nature of the instruments being used. For example,
should pressure not be placed correctly the wells would overflow. Also, when the syringe was removed
the lack of suction allowed the fluid to flow into the other wells from either the channel or staging well.
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Due to the nature of the size of the chips cleanliness is an important aspect to address. While handling
the chip it is recommended that the handler wash his or her hands and then wear gloves so as to not
compromise the chip with the dirt from his hands onto the chip. Another practice involves minimalizing
the space that the chip is moved. Since the computer lab is not a state-of-the-art nanotechnology
facility with dirt elimination the amount of time from the chip being cleaned to being tested should be
minimalized so as to decrease the chance of dirt interference. Finally, when testing the chip the surface
that the chip is placed on should be thoroughly cleaned as well—while the surface of the dish will not be
touching the interior of the chip, the lack of dirt will increase chances of success.
To further in the cleanliness of the environment external devices would have benefits. The use of a
sterilized petri dish with a lid would greatly aid in the transport of the chip, keeping contaminates from
the air away from the chip itself. A must when handling the chip is to wear latex gloves so as to keep
oils from the hands away from the chip. As with cleaning the chip, a precise instrument is necessary to
produce the best results, therefore a water pick would be ideal with cleaning the various canals and
wells cut in the chip. While there are many other fine-tuned instruments ideal for cleaning a micro-sized
chip, the listed few are only a couple examples of those instruments.
While the format our chip is being made for is to test for the presence of “dry-eye” syndrome, the chips
can act under a variety of purposes. Another possible application is to test for the presence of
contaminants in waters and river. Only a small portion of water would be necessary, allowing the chip
to serve its purpose well. Another potential application is to aid in the use of detecting diseases in thirdworld countries. Since the chips can be made cheaply in mass quantities and are similar in function to a
blood glucose meter, the devices could be used by trained professionals overseas to test for and locate
cases of certain diseases—ebola, malaria, measles, etc. This would allow the diseases to be discovered
quicker and thus, allows time for an efficient plan of action to manifest before the disease spreads.
Given the context of its use the generic chip design could be altered so that there are fewer wells. Since
5 wells were present on the chip there was less surface contact between the two halves of the chip to
allow for an air-tight seal. Should there be fewer Staging wells the structure may not be as
compromised and allow for the passage of water more smoothly. Another change is that the capillary
check valves could be made larger so as to further slow the progress of the fluid. This would allow a
more precise amount of fluid to be introduced to the chip.
NTM Questions
Because of its size nanotechnology does not require as much capital or natural resources in order to
create an equal number of products. Also, because of its size the devices can be transported easily as
well as used in both formal and informal settings—a hospital, a patient’s home, or in the wilderness.
With these devices results can be achieved at a much more rapid pace, as opposed to sending samples
to a laboratory hours away. This speed and maneuverability allows for doctors to arrive at important
medical decisions in a timely manner, decreasing the amount of time for a patient’s disease to become
worse or infectious. Traditional metal wires have a high resistance over long lengths, however, with
nanotechnology information can be spread at a more rapid pace. This would allow ideas to be spread
with more ease, from even the remotest portions of the world.
Because of the difference in size between nanotechnology products and bulk products, the stress
allowable on the objects differs greatly. Cement blocks, wooden beams, etc. are perfect candidates for
structural items because of their size and relative ease in maneuvering. While carbon fiber is often used
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as structural support on bicycles, planes, and other items with large amounts of stress, the product is
much costlier to create, and thus less cost effective. The micro-chips that our group will be creating
over the next semester are not used for structural purposes, therefore, if they were to be produced in
bulk they would need to be housed inside another component capable of compensating for the lack in
stress acceptance of the chips. While their use at the molecular basis is extensive, the downside is that
the chips must be created and handled with care. One current application of nanotechnology is for
forensic analysis at the scene of the crime. One future application of nano devices is to control the flow
of individual DNA strands to be analyzed at specific points on a chip.
Conclusion
The goal of this lab was to experiment with and analyze the performance of a generic PDMS chip that
the team’s future micro-chip will be based upon. By cleaning and testing the chip the team was able to
understand the intricacies of the chip design as well as understand the importance of proper cleaning
and maintenance of the chip. The proper equipment, procedure, and work environment allows for the
least amount of contaminants to come in contact with the micro-chip as even the smallest amount of
dirt can interfere with the results from the tests.
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