Memo
Date: January 20, 2015
To: Inst. Trott and GTA Mohini Dutt
From: Joshua Epperson, Brooke Ott, Benjamin Weisman, and Luisa Parish
Subject: Introduction to Lab on a Chip
Introduction
This experiment allowed the characterization of the polydimethylsiloxane (PDMS) chip. The
goals of the lab was to observe how the dyed water flowed through the PDMS chip and
what characteristic worked best in the staging wells, detection well and waste well. The
experiment involved dyed water so the flow of the water could be easier to see and clear
water to flush the system to test a new staging well. This memo contains the observations
of the flow of water as well as the best characteristics for the PDMS chip. The experiment
was conducted by group R which consists of Luisa Parish, Benjamin Weisman, Brooke Ott,
and Joshua Epperson.
Results
Depending on the well that was filled the colored water travelled differently. All of
the wells had check wells. When performing the experiment there was an issue with the
holes to the staging wells not lining up properly. The staging wells were labeled 1 to 5 with
1 being the one closest to the team label and then going counter clockwise to 5. If the wells
were aligned to wells 2, 3, and 4 the holes would not line up with 1 and 5 at the same
time. It had to be one or the other.
For each staging well the liquid filled the staging wells before going into the detection
well. Well 1 did not fill up itself but made the other staging wells overflow. Well 2 filled
completely and the fluid began to go down the channel towards the detection well; however,
the fluid began to overflow from the top because the syringe was too full. The check value
worked well and the the liquid stopped at the detection well. The colored liquid, depending
on were pressure was put, flowed outside of the channels between the two layers. Because
of this more pressure was put near the staging well but the water went between layer in
different locations. Also when removing the syringe from well 2 liquid came out of the
opening when the syringe was successfully removed. This could have been because there
was a suction effect with syringe and the PDMS chip. Well 3 was similar to well 2 but it
worked slightly better. It filled all of the staging wells and then filled the detection well and
the waste well. Like well 2 the syringe created a suction and some of the water came out of
the hole in well 3 when the syringe was removed. Well 4 worked occasionally based on
where the pressure was put on the PDMS chip. Water would go between the two
layers. Well 5 was similar to well 1. The water overtimes over flowed from the hole and
went in between layers.
When observed with a magnifying glass details in the chip were seen. In well 2
there was some debris that was not removed when the chip was cleaned and this could
have interfered with the flow of the colored liquid. Also in well 2, 3 and the waste well had
slits in them.
Discussion
Factors that affected the chip’s ability to perform include varying pressures and
pressure points, the cleanliness of the chip, and the varying positions of the wells. Below
are ways to fix the issues stated before.
The pressure allowed a vacuum to be present in the channels which allowed the
water to flow into the detection well more easily without water getting in between the two
layers of the chip. The best case scenario would have the chip have uniform pressure
Memo
Date: January 20, 2015
To: Inst. Trott and GTA Mohini Dutt
From: Joshua Epperson, Brooke Ott, Benjamin Weisman, and Luisa Parish
Subject: Introduction to Lab on a Chip
through the chip. This would help the wells such as 1 and 5 from dispersing water in
between the layers.
In regards to the debris found in well 2 the chip should be washed and dried with a
Kimwipe more thoroughly and the side that has been washed should not be touched by
fingers or placed down on the table. Also blowing air through the wells may help with the
issue of debris getting stuck into it and it would dry the chip. For this experiment distilled
water was not used to test the chip. Instead of using tap water distilled water could aid in
keeping the chip more clean.
Lastly, to solve the problem of the varying positions of the holes in the staging wells
more accurate the chip top layer should have been put on top and then using a marker to
place the holes. The holes should have been measured to the center of each staging
well. Also to keep the water from entering all of the staging well before entering the
detection well, the staging well’s holes should be closed which would leave the waste well
the only method of escape for the water and the air.
This chip could have been used for detection of fluorescein in the eye and the
concentration of i within the eye. This can be tested by added on chemical in one stage
well and the teardrops in another. When they meet in the detection well depending on the
color formed and its intensity that would help determine the relative amount of fluorescein in
a person’s eye.
The chip could be improved as stated earlier if the holes into the staging wells could
be closed or the channels could be cut off from the staging well that is having the liquid
being injected into it.
NTM Questions
Nanotechnology allows the observation and manipulation of individual atoms, which
is something that could not be done before the invention of the scanning tunneling
microscope (STM). As the means of interacting with atoms increased governments such as
the US has been funding programs to research and develop applications of
nanotechnologies.
There are two theories in physics: classical mechanics and quantum
mechanics. Classical mechanics focuses on what we can see and quantum mechanics
focuses on molecules and atoms and how they interact. Classical mechanics allows us to
predict where an object will be and where it used to be giving it a sense of
certainty. However, quantum mechanics does not have this same certainty or
predictability. It allows us to guess where an electron is but it cannot be seen to be
proven. At some point the classical mechanics starts to go into the quantum mechanics
and in this area of transition is where nanotechnology comes into play and what it deals
with. Atoms behave differently at this small scale than what the eye can see. There have
been many applications of this phenomena and many more can be discovered. For
example, the tennis balls, Wilson Double Core, used in the Davis Cup tournament has a
clay nanoparticle lining which allows air to escape from them. The tennis balls last twice as
long with that adaptation. An example of a future application that may use
nanotechnologies would be ability to detect biological warfare agents with
nanosensors. This could be used as a defense against those agents.
Chip Design
Memo
Date: January 20, 2015
To: Inst. Trott and GTA Mohini Dutt
From: Joshua Epperson, Brooke Ott, Benjamin Weisman, and Luisa Parish
Subject: Introduction to Lab on a Chip
The sketch of the chip is attached to this lab memo. The chip is designed to be 5.08
cm in diameter and 5 mm thick. The depth of all the features (detection well, staging wells,
and channels) are 200 microns deep. Also the channels will be 350 microns wide. All of
the wells will be in the shape of a circle. This is because it makes it easier to flush out with
water. Also in the staging wells a small slit will be added because this worked the best in
the experiment. All of the components have to be 1 cm away from the edges so that the
chip does not break. Lastly an R will be put on the chip to specify which group the chip
belongs to. Also each staging well has a check valve. This will only allow a liquid or gas to
flow one was through the channel. This makes a vacuum and the liquid will not escape out
of the other staging wells.
Conclusion
The purpose of this experiment was to observe how the dyed water flowed through
the PDMS chip and what characteristic worked best in the staging wells, detection well and
waste well. It was determined that the staging wells with the slits in place as well as a clean
chip. Also the check valves if they worked correctly then the leaking of the water would not
have been an issue. The proper equipment would allow the chip to work much more
effectively. For example if the holes to the staging wells lined up then wells 1 and 5 may
have worked slightly better.