Memo
Date:
To:
From:
Subject:
January 27, 2015
Inst. Bruce Trott and GTA Mohina Dutt
Group R- Ben Weisman
Introduction to Lab on a Chip Lab
Introduction
The tasks performed in the Introduction to Lab on a Chip Lab allowed for experimentation with a general
lab-on-a-chip. The performance of many chip features were tested, recorded, and evaluated. The
information gained through testing will be applied during the chip design and fabrication process. Also,
knowledge on the importance of following lab procedure and using proper equipment was gained. This
memo contains the results of the testing as well as a discussion of the chip and lastly conclusions drawn
from experimentation. Joshua Epperson, Brooke Ott, and Luisa Parish also participated in the activities
that this lab entailed.
Results and Discussion
The chip was tested by adding liquid to each of one of five wells. Each well was first labeled; if looking at
the chip from above, well one was assigned to the well farthest on the right of the chip (closest to what
would be the 3 o’clock position if looking at a clock). Wells two through five were assigned by starting at
well one and going counterclockwise around the chip.
Wells one and five performed the worst of all the wells. Whenever wells one or five was filled a
substantial amount of fluid would begin to overflow from the well instead of going into the channel
connected to the well. The liquid that did flow into the channels did not flow directly to the detection
well and into the waste well. Instead, the liquid would flow up the channels connected to the rest of the
staging wells and into them. However, the check valves associated with wells one and five appeared to
function properly.
Well four performed third best of the wells. The well would not overflow, but rather would leak and
allow fluid to slowly but continuously leave. Well four’s check valves appeared to function properly, and
just like wells one and five, whatever liquid did flow into the channels would flow up the channels
connected to the other staging wells and fill them while also flowing into the detection and waste wells.
Wells two and three both performed the best. Neither well would overflow when liquid was added. Well
three would overflow occasionally when the syringe used to pump liquid into the well was removed. The
check valves for both wells appeared to function properly. Similar to all the other wells, liquid would
flow up the other channels and into the other staging wells while simultaneously flowing into the
detection and waste wells. When investigated with a magnifying class, wells two, three, and the waste
well appeared to have a fine slit running through a diameter of the well. Perhaps this slit allowed small
amounts of fluid to enter it first, then allowed fluid to fill up the well. This could be the reason wells two
and three did not overflow. Small amounts of debris were also found in well two.
The biggest factor preventing a successful chip design appears to be keeping the wells from overflowing.
Many factors could go into the overflow of a staging well. The rate at which liquid is pumped into the
well along with location and magnitude of the pressure is applied on the PDMS chip by an operator (e.g.
if more pressure on right side of PDMS, liquid will flow out left side) could cause the well to overflow.
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This improper pressure factor could have been a possible source of error; the functionality of a well
could have been misjudged because of improperly applied pressure to the surface of the chip.
Impurities, such as the debris observed in well two, could also hinder a successful chip. Debris could
easily clog a channel or well and not allow fluid to flow through it. Cleanliness, therefore, is very
important and must be maintained. The chip should be cleaned before use and after every test. When
cleaning the chip, water and KIM wipes should be used. Touching the surface of the chip and bottom of
the PDMS chip (the surfaces that will come into contact) should also be avoided. Impurities from the
hands could contaminate both chips.
Some external devices needed for use of the chip. KIM wipes and water would be needed to clean the
chip and some sort of glass or plastic case would be used to transport and store the chip in. A syringe
would be needed to introduce liquid into the chip and gloves would also be needed to handle the chip
properly without contamination and to keep potentially hazardous fluids being injected into the chip off
the skin of the operator.
The chip has many possible applications. For example, medically, the chip could be used to measure
small volumes of liquid medications to be administered to patients. Also, it could be used to help with
testing blood sugar levels of diabetics. Lastly, the chip could be used to mix small amounts of chemicals
and observe their reactions.
The chip used in this lab could be improved. Staging wells should be placed higher than the detection
and waste well so that the channels are angled downward; allowing gravity to help move the fluid
through the chip. Also, this angling of the channels would help prevent fluid from flowing back into any
of the staging wells. Furthermore, all of the channels should be straight lines that flow directly to the
detection well. The rounded corners and edges of the chip used in the lab could have allowed some fluid
to be caught in them, meaning a less efficient chip.
Nanotechnology allows many capabilities that were previously not feasible. At the nano scale, the
properties of many objects change. Scientists and engineers working at that nano level now have
unprecedented control over the properties of certain substances. For example, scientists could create a
very strong nano-material that is very light. A material like this could revolutionize both aerial and land
transportation. One example of a material that behaves differently on the nano scale is gold. Gold
appears yellow in color to the naked eye, but at the nano level it appears red. One current application of
nanotechnology is genetically modified foods, these are crops that are genetically manipulated for
human consumption. A future medical application of nanotechnology is injecting a cancer patient with a
nanoparticle that could be used to destroy a tumor.
Initial Chip Design Sketch
Attached is a sketch of a chip design for a 4-hole chip holder. The chip consists of four staging wells a
detection well and a waste well. Each staging well has a channel attached to it that runs directly to the
detection well; the detection well has 3 channels connected to it running to the waste well. The three
channels running from the detection well to waste well are to allow a greater volume of fluid to flow
more quickly into the waste well. As seen in the sketch, the waste well appears to have a banana shape
that curves back toward the center of the chip. This shape is designed to increase the amount of
substance the waste well can hold.
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Conclusion
In conclusion, through the completion of the goals associated with this lab, the team became more
familiar with a general chip design and how all of the features of the chip design function. It became
obvious in the generic chip that not all of the wells functioned the same, some would overflow (wells 1
and 5), others would leak (well 4), and some functioned almost flawlessly (wells 2 and 3). It became
obvious during experimentation that following lab procedure and using suitable lab equipment would be
crucial for the fabrication of a successful chip. In order to avoid many of the shortcomings of the generic
chip (well overflow and leakage) the group must adhere to laboratory procedure and understand how to
properly use laboratory equipment. Lastly, it can be noted that the team worked best during lab when
the work environment was positive, and every group member was involved. This positive, involved work
environment will be critical in designing a successful chip.
Error appeared to be minimal during experimentation. One source of error mentioned earlier was
inconsistent pressure being applied to the PDMS chip may have been responsible for well overflow,
which may have caused the performance of each well to be misinterpreted. This error was noticed
during experimentation and an attempted correction was made by doing multiple tests on each well. By
doing multiple tests, it was more likely that proper pressure was eventually applied and when consistent
results began to occur, it became easier to judge the effectiveness of each well.
Overall the experiments contained in this lab helped group members become more familiar with generic
structure and design of a chip as well as uncovering some potential areas of concern to consider when
designing a chip (such as well overflow and chip contamination). This information can now be applied
during the chip design process to make the chip better and more efficient.
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