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Phase V: Conduct PIV Study
Month of December

What have we learnt?

• We have learnt how to set up the equipment and apparatus to create a height difference to produce a pressure-driven flow.

• We made use of the Dynamic Studio software to study the particles flow under pressure-driven conditions using various PIV correlations methods.


• We carried out two experiments: two inlet streams without height difference and two inlet streams with height difference.

• For two inlet streams without height difference, the flow is relatively laminar due to low Reynolds number. Mixing is negligible and the flow is towards one direction.

• For inlet streams with height difference, the flow is near to turbulence due to higher pressure applied. Moreover, at the junction where the two inlet streams meet, some mixing is observed from the vectors diagram obtained. However, after the junction and towards the straight channel, the flow becomes laminar and more orderly. Mixing is not observed in that section.

• In short, Reynolds number and pressure do affect flow regime in micro-channel and also contribute to mixing.

Equipment Set-up

As mentioned in previous log entry, we placed our micro-slide on the stage and use the microscope to adjust the focus settings. In Dynamic Studio software, we had to manually re-adjust the knob again to get a better focus on the channel image since the focus on the micro-scope and the focus in the software are different.

Next, the two inlet streams of the micro-channel are connected to two syringe tubes which are then attached to two different syringes. For the first experiment with no height difference between the inlet streams, both the syringes were suspended at the same level above the ground. The syringes were supported with a retort stand. In the second experiment, one inlet syringe is placed at a higher elevation than the other stream to create a height difference.

As for the outlet stream, a syringe tube is connected from the channel outlet to a syringe which is suspended at a height level below the inlet two inlet streams. By doing this, we are creating a pressure-driven force in which the two inlet streams at higher elevation will travel towards the outlet at lower elevation. This is true since the as the height from the ground increases, pressure will also increase.


Dynamic Studio

After the set-up, we carried out our experiments using the Dynamic Studio software.
At the start, calibration is carried out to obtain the the width of the channel so as to obtain the vector, the speed at which the solid particles are moving.

Next, after carrying out pre-experimental settings, the actual acquiration of images is performed. After that, using the images captured, we performed various cross-correlations and masking PIV techniques to get reliable vector diagrams which represent the actual flow of particles. Unwanted regions and vector arrows are removed and masked off. Only wanted regions are kept.

Experiments

Our purpose of doing an additional experiment in which there is height difference between the two inlet streams is to study whether turbulence will be experienced in such condition. Furthermore, by having two different variables, we can make comparisons in our results to note any difference in observations in terms of flow regimes and presence of mixing as well as results.

Problems Encountered / Solution

Several of the problems encountered include problem in removing air bubbles, and distribution of light source on the micro-channel. Removing the air bubbles is a difficult task as the tube is required to be flushed completely with the liquid. At the same time, there is a risk of forming new air bubbles. In order to counter this, we had to flush the tube with the liquid very slowly and patiently so that the probability of forming new bubbles is decreased.

Furthermore, ideal distribution of light source on the channel is also hard to achieve as the light source will never be evenly distributed throughout the image of the channel. In our case, when adjusting the light source, the light was either too concentrated on the channel or too dim. These problems will affect our results especially during the PIV techniques application is performed. As a solution, we adjusted the brightness and the position of the micro-strobe to ensure the light is not too bright and not too dim and focus on the section of the channel which we are interested. Unwanted regions are purposely left in the shadows.


Phase VI: Electro-kinetics

In this phase, we are basing our project on past year’s FYP project on micro-pumps and will be going into further observatory details. We are able to conduct further observatory studies through our FYP’s topic and equipments using micro PIV. This enables us to see how particles flow from one point to the other than just 1 particle by calculating manually the speed of the particle. By having this micro PIV, we are able to see how fast is each particle is moving and in what direction in vector charts by using the micro PIV software. By re-conducting the experiment the previous group has done earlier, we are able to see it visually how the particles move and behave under electric supply. For example, by studying the vector charts a little more detail, the particles vibrates forward and back ward while moving, the particles move from the negative to the positive thus it is suggested that this is caused by electrophoretic forces and electro-osmotic forces acting together.
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Months of October and November

Phase III: Make mould using SU-8

The procedures of this phase are exactly the same as in phase 2 but the main difference between the 2 stages is, in phase 3, there is no more testing of thickness of any trial and error. The layer of SU-8 spin coated on the glass piece is chosen at 1000rpm.

The only test we made was to draw up a few shapes to see if UV light was able to pass through which type of ink from 2 markers. This is important as the print job is not perfect and the ink coated on the transparency is uneven thus UV light is able to pass through these area. Having this problem, we can use the proper marker to draw over these ‘holes’.

The finalised mould design is shown below.



Problems we faced and solutions

When colouring the mould design after printing

After printing, the result of the mould design is not really black. A marker is needed to colour the blacked-region of the design so as to prevent UV-light to pass through.
The problem occurs when colouring, some of the ink smudges to the designed channel area.

Solution

We print out on another piece of paper then cut out the respective design and paste it behind the pattern being printed on transparency using double sided tape


Phase IV: Familiarize and Make chip using PDMS

What have we done?

1) Mixing the PDMS

-PDMS mixed in a 1:10 ratio of curing agent to PDMS monomers base.
-Curing agent will cure the viscous PDMS base.
-Mixture stirred for 3 minutes to ensure uniformity.
-After 3 minutes of stirring, many bubbles are formed.

2) Degassing of PDMS

-Degassing is done to remove bubbles in the PDMS.
-PDMS in cup is placed in the desiccator connected to the vacuum pump.
-Aluminium foil is placed below the PDMS cup to catch any PDMS that spills out of the cup.
-Vacuum pump set at low level (around -200) to allow bubbles to rise up and burst at the surface.
- * Too high vacuum cannot be used as it will cause the PDMS to boil off making the PDMS even more viscous.
-May damage vacuum pump.
-Degassing duration is around 1-2 hours.

3) PDMS Pouring

-After degassing, PDMS is taken out.
-The mould is placed on an aluminium foil on top of a plastic Petri-dish and wrapped the inner side of the Petri dish.
-The aluminium foil wrapped container will contain the glass mould piece so that the PDMS can be filled into it. The purpose of doing this is for easy removal of the PDMS after solidifying instead of sticking onto the Petri dish..
-After that, the PDMS is poured slowly and near to the glass mould piece surface to prevent formation of additional air bubbles.
-The amount of PDMS poured depends on the thickness we want for the PDMS mould. In our case, its about 1mm thick.
-After ensuring the PDMS is evenly spread out, the Petri-dish can then be placed in the oven for 4-6 hours minimum at 60°C. To achieve optimum results, it must be baked for 8 hours in the oven at 60°C.

4) PDMS Unmoulding

- After taking out the PDMS mould from the oven, it is left to cool for about 10 minutes.
- For better efficiency, excess aluminium foil at the side of the PDMS mould is removed.
- Using a pen-knife, aluminium foil at the bottom of the PDMS mould is slowly and completely removed.
- After that, the pen-knife is inserted in between the PDMS mould and the glass piece edge.
- Then, carefully and slowly, the knife is slit around the edge of the PDMS mould and occasionally is inserted deeper to allow the mould to detach from the glass piece.
- After the edges of the PDMS mould is detached from the glass piece, it can be slowly peeled off using hand.
- *Be gentle and extra careful as the PDMS mould is brittle and may break easily.

5) Cleaning

- After cutting out the wanted PDMS layer, wash the layer with soap.
- After washing the layer with soap, rinse it with De-Ionized water.
- For the final washing, rinse it with Isopropyl Alcohol (IPA).
*- After rinsing with IPA, dry it by putting inside the Petri dish and cover it so as to prevent any particles or dust to stick on it.
*note: For proper procedures, after rinsing with IPA, it must be dried using nitrogen gas. Since we do not have a nitrogen gas air gun, it was left in the Petri dish covered and evaporates by itself.

Problems Encountered

i) Zero Error in Weighing Scale. Inaccuracy in weight measurement.

Solution
To overcome this, zero error has to be minus off from reading measurement.

ii) Plastic cup too high to be placed in the desiccator.

Solution
To overcome this, before the PDMS is prepared, the plastic cup is shortened to a height which can fit into the desiccator.

iii) During the PDMS pouring, the PDMS is unevenly spread out on the glass piece. This will cause the PDMS mould layer to be uneven with one side thick the other side thin.

Solution
To overcome this, a suggestion will be to pour the PDMS from the centre of the glass piece to allow more even spread in all directions.

iv) During the PDMS un-moulding, the PDMS mould could easily be damaged or destroyed when not properly handled.

Solution
To prevent this from happening, the aluminium foiled area is removed to the table and a penknife is used to cut round the glass mould. By doing this, it minimizes the chance of the PDMS to be damaged. After cutting, fold the areas at the side of the glass and the wanted area can be taken off the aluminium foil easily and the PDMS on top of the glass mould can be peeled of slowly and easily.
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Month Of September

Our project has been segregated into 6 phases. In this project we come across many new and different chemicals and procedures, the phases are allocated by us so as to give us a target to familiarize with these new procedures and chemicals so as to prepare us for the future portions of our project.

This is done so as to allow us to know the purpose why we are repeating the procedures over again and again. Doing these phases is also a time gauge and target for us to meet and also to what extend we have completed our project to.

In this project the 6 phases are:
Phase 1: familiarize with micro PIV
Phase 2: familiarise with SU-8
Phase 3: mould making
Phase 4: Familiarize with PDMS and making of final chip using mould
Phase 5: Conduct Micro PIV (pressure driven) study
Phase 6: Electro kinetics micro PIV study


Phase I: Familiarize with PIV
Week 4 to 8 of FYP as stated in the earlier log reports

In order to start this project, we must first familiarize with the equipments needed for this project and also how we are able to study the flow pattern within the chip using the software which comes with the equipment. In order to get ourselves familiarize with the system, we make use of the given chip and make ourselves familiarize with the whole system. By doing so it also gives us an idea on how we are able to plan out how we are able to study flow at which areas in the latter part of our project.

Below are the procedures on the micro PIV system and the software.

1. Calibration

1) After focusing, we must change to single frame mode and acquire. The reason this is being done is to do calibration of the width of the channel so as to obtain the vector, the speed at which the solid particles are moving. After we acquire, we switch the window to acquire data to save the image under calibration. Exit acquisition mode. Under the database that the image is saved in, select the image under calibration.

2) Open the image and right click on the image. Select measure scale factor.

3) In the new window that is opened, click on absolute distance and type 1mm (since the distance between opposite walls in the straight channel is 1mm).

4) Then, select X-Y markers below. Using the instructions given, mark points A and B on the image which represents the respective points on opposite walls.

5) Once done, the scale factor will be shown on the right hand side. Calibration is complete.

2. Pre-experiment settings

1) Click preview under system control

2) Estimate the speed of the particles from the ‘preview mode’ and adjust the time between pulses for each frame.


3) Adjust the number of Hertz (Hz). The Hertz value is the number of shots one want to take per second.

4) After setting from step 1 to 3, now select ‘double frame mode’ under system control.
3. Experimental imaging process

1) Use the settings from step 2.1 to 2.4 and click run on ‘double frame mode’
2) Click on ‘acquire’ to view images and save it.
3) After saving images, clear buffer space.
4. Experimental Images analyzing

1) Left click once on saved set of images to highlight the file, and then right click, select analyze.
2) Under analyze, select cross correlation, under cross correlation, go to the option ‘select interrogation areas’.

5. To get rid of unwanted regions on images so as to see a clearer vector image (optional)

1. Right click on ‘saved images’, select ‘analyze’.
2. Under ‘analyze’, select ‘image processing’.
3. Under ‘image processing’ select ‘image mean’ and then press ‘ok’.
4. After obtaining the image mean, right click, select ‘image mean’ obtained from the step above.
5. Go to Image Arithmetic, under ‘Image Map’ select ‘subtract’. This function subtracts the ‘image mean’ from the saved images so as to obtain the channel containing the particles in each saved image. This is done so as to eliminate any waste images which will affect the result due to unwanted vectors.
6. Under ‘Constant’ select ‘multiply by’ constant value ‘X’. ‘X’ is up to one to set. The constant value sets the image clarity.
7. If the resulted images is still not clear, right click on the images, go to ‘display option’ to set the gray scale.
8. Result.
9. To analyze the new set of images, select the file, select ‘analyze’ and then select ‘cross correlation’ to obtain the final vector image.


Phase II: Familiarize with SU-8
Completed on the month of September

In this phase, we split into two phases, one is to practise with an ‘expired’ SU-8 to familiarise with this chemical and the other is to find how different spinning speeds affect the coating thickness.

The first objective, being new to this chemical, we learn how to apply the SU-8 on our project by following the manual provided by the vendor and also understand it by practising a few times to familiarised it before making our final mould. In order to achieve perfection and true understanding of the chemical thus we use the expired SU-8 given by the vendor to practise. By doing this, we will be able to achieve perfection then we can carry on using the actual bottle that was purchased so as to prevent wastages.

Our second objective is to find how different spinning speeds affect the thickness of the SU-8 coating on the glass piece. This is very important as it plays a crucial part in this project. Although all the thickness in all spins are acceptable as our particles for micro PIV is 1 micron, the thickness allows us to make the chip easier and also handle it easier. The reason behind this as we are doing the chip for the first time.

SU-8 is a high contrast, epoxy based Photo resist designed for micromachining and other microelectronic applications, where a thick, chemically and thermally stable image is desired. Film thicknesses of 0.5 to >200 microns can be achieved with a single coat process. The exposed and subsequently thermally cross-linked portions of the film are insoluble to liquid developers. SU-8 has excellent imaging characteristics. SU-8 has very high optical transmission above 360 nm, which makes it ideally suited for imaging near vertical sidewalls in very thick films. SU-8 is best suited for permanent applications where it is imaged, cured and left on the device.

Spin-coating with SU-8 at different speeds

Before spinning can be conducted, the Su-8 chemical must be de-gas using the convection oven for half an hour to an hour at 60 degrees C any higher temperature cannot be used to speed up the de-gassing as the Glass transition temperature (GT) is at 65 degrees C even if at a higher temperature, it may distort the chemical properties of the SU-8 and form unnecessary bonds. Heating was chosen as it helps thins the SU-8 chemical and let air escape as SU-8 is a very viscous chemical. After heating there will still be a little air bubbles mostly on the top layer of the SU-8 chemical in the beaker. Leave the beaker of SU-8 at room temperature to cool it. After cooling there will not be any air bubbles

i) We carried out spin-coating with SU-8 on 3 glass pieces at speeds of 2000rpm, 1500rpm and 1000rpm respectively.
ii) After spinning, we soft-baked the glass pieces in the oven at 95°C for 5mins.
iii) The glass pieces are then cooled down to room temperature.


Results

We are unable to measure the exact thickness but according to the table provided by Microchem, the results we obtained will be the same as theirs.
The results for SU-8 2025, trial chemical are:
At 2000 rpm, 40 microns
At 1500 rpm, 60 microns
At 1000 rpm, 80 microns

The results for SU-8 2075, actual chemical are:
At 2000 rpm, 110 microns
At 1500 rpm, approx 170 microns
At 1000 rpm, 240 microns

Procedures for masking and developing

After choosing a design to be masked on the glass pieces, we exposed them under UV light for 50s.

i) Then, we place the glass pieces in the oven for 5mins at 95ºC for Post Exposure Bake.
ii) Then, we cooled down the glass pieces to room temperature.
iii) After that, we dipped the glass pieces in the SU-8 developer for 5mins.
iv) Lastly, we rinsed the glass pieces with Iso-Propanol followed by water.

For further details, an SU-8 2000 series manual will be attached at the back of this log.


Difficulties faced and solutions that can minimise the effect.

SU-8 2075 and 2025

Problems encountered,

Dimples formed on SU8 layer during heating

This happens as the glass piece sits on the hot plate at 65 degrees then the temperature is ramped up to 95 degrees causing the SU8 to stretch and cause an adhesion effect where by the SU8 stretches and causing some parts to sink down causing a "dimple effect".

Solution
The proper way to do it is to use 2 hotplates one at 65 the other at 95 degrees C

SU-8 must be soft bake immediately, if exposed to the environment, dust will stick on the SU8 layer.

This problem can be avoided when both hot plates is available.

Wave-effect after soft baking

This effect is caused by the spinning effect while spreading the SU8 onto the glass... This effect is caused by the vibrations of the machine while spinning especially at low speeds like 1000rpm that my group had experienced.
This wave effect have minimal effect on SU8 2075, we assume that the viscosity of the liquid do play a part as the wave effect so far effects the SU8 2025 that we have as a trial chemical


Solution

This cannot be avoided but can be minimized for thick SU-8 coating and spinning at low speeds example 1000rpm. However, this problem can be eliminated if the thickness of the SU-8 layer is thin and the speed of the spin coater is high example 3000rpm.
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Month of August

Break & Revision

EXAMS
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enjoy :)














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25 july 2008

What was done

After being briefed about the status of our project the previous week, we proceed with our trial and error in making the micro channel chip usingthe SU-8.

This week focuses on finding the proper way to develop the SU-8 photoresist without affecting the chemical.

We started off by putting the glass pieces under UV light in which a stencil is placed over it to get the desired design that we wanted. This procedure is called UV masking.

Following that, the glass pieces were then heated up again. A point to note is that the heating up of the glass pieces in the oven SHOULD take place immediately after the UV masking. This step is called the post exposure bake.

Following that, the glass pieces were then left fully submerged in a beaker of the SU-8 developer. The glass pieces were then rinsed with tap water for about 10 seconds before being soaked into a beaker of Isopropyl Alcohol (APA) for another 10 seconds.

The end product

Recommended program:

UV masking
We used a stronger UV light machine. Thus, the energy emitted was 150-160MJ in which the glass pieces were exposed for a time of 13 seconds.

Post Exposure Bake
The glass pieces were heated in the oven for 1o minutes.

Developing
This took some time for perfection as the SU-8 always comes of for the first few runs. But we managed to get it right after several tries. The glass pieces should be soaked in the developer for 10 minutes. Not longer than 11 minutes.

Conclusion

For an experiment that was full of trial and error, we did quite well as we managed to find the proper timings in making a good mico channel chip. Though this week was quite a success since we exceed expectations in finding the right blend of timings, we should not be too complacent. This is due to the fact that we have yet to find a way to stick the glass pieces together without melting the micro channels form on the glass pieces. Till then, we have to be constantly be on our toes.

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18 july 2008

What have we done?

· Learning from Mr Ting more details about making our own micro-chips using SU-8.
· Obtaining references for further reading regarding fluid flow in different micro-channels.
· Propose a plan for activities to be done in July, August and September.

What have we learnt?

We have learnt theoretically from Mr Ting on how to make our own micro-chip from SU-8. He told us that common manufacture of micro-chips from SU-8 requires a mould to be made. However, to save time and materials, he suggested that we try to directly produce the cast without having to create the mould. This procedure has not been tried before but that does not mean we cannot try out. Hence, we have decided to make use of the expired SU-8 as a trial to find the best methods to create a reliable micro-chip.

Some Problems encountered

· Since our project is research-based, at some point of time we found ourselves not knowing what to do next.
· Having doubt as to whether we are able to make our own chips.
· Our schedule seems to be changing as our next step is unknown.
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enjoy :)

















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11 July 2008

What was done

We did a continuation of what we did last week which is to make our own micro channel chips.

Before doing anything to the glass pieces which had been left in the lab for a week, we had to heat up the glass at a temperature of 280 degrees Celsius for 10 minutes. This is to prevent any contamination that might have been on the glass pieces and also to ensure the ‘stickiness’ of the glass for the spin coating later on. We also heat up a small beaker at the same conditions for the same reasons.

The SU-8 was then poured into the beaker ,after it had cooled down, to about ¾ full. Following that, the SU-8 was then put in small quantities onto the glass pieces for the spin coating. After spin coating, the glass pieces were then for soft baking.

The recommended program for chemical SU-8 2025

Spin coating
Based on the dimension of our glass piece, 4-5mL of SU-8 was poured with slight excess onto the glass piece as the recommended volume to be poured on to the glass is 1ml per 25mm. Spin coat the glass piece twice with the first one at 500rpm for 5 to 10 seconds with an acceleration of 100rpm/second and the second one at 3000rpm for 30 seconds with an acceleration of 300rpm/second.

Soft baking
It is best to bake on a lead hotplate with good thermal control and uniformity.
For the size of our glass piece, it was bake at a temperature of 65 degrees Celsius for 0 to 3minutes then at 95degrees Celsius for 5 to 6 minutes.

NOTE: After removing the glass piece from the hotplate, be careful of the hot glass pieces. Allow the glass piece to cool. If wrinkles appear, soft bake the piece again at the same temperature at 5 minutes interval. Repeat until there are no more wrinkles on the glass piece.

Problems

There is only 1 problem, which are the air bubbles in the SU-8. We will try to solve the problem but we have not encountered any big problems till date as our SU-8 coating is very thin. Our problem may or will arise in the latter part of this phase when dealing with a much thicker coating

Conclusion

Though this week’s experiment might have been a short session, it was worth noting that we familiarized ourselves with the same equipments we used at the start of our FYP research. Also, we cannot proceed on with the making of the micro channel chips as the chemicals needed for developing the glass pieces are still not ready. Hopefully, the chemicals will be ready next week. If not, we can always start again with the PIV equipment.

This is still early of part of our development of using SU-8. By having this experience from these 2 weeks, it will be a stepping stone for to learn more about this chemical and how to handle it properly. This is because this is our first time handling with this chemical. By having this experience we can also predict what problems it may occur.
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4 July 2008

What was done

Basically, we started to make micro-channel chips again. This time with the SU-8 photo resist which is to familiarize ourselves in making the chips when the real materials come in a few weeks time.

Like the previous experiment that we did in the first 3 weeks, the same procedures can be applied to this week’s experiment.

We started by cutting the glass into smaller desired pieces before the edges were blunted. This is to prevent the glass pieces from having sharp edges which may cut our fingers when handling it. The glass pieces were then rinsed several times so as to ensure that the glass pieces are sterilized.

We ended the experiment by heating up the glass pieces to dry and disinfect in at the same time at a temperature of 200 degrees Celsius for 30 minutes. The glass pieces were then left to cool before being stored at a safe place.

Conclusion

We did not manage to complete the experiment as there was not enough time. Though there was a lot of waiting time, we managed to use the time efficiently by reading up on the chemical SU-8 which will be useful for next week’s experiment. We hope that we can have enough time to play around with the chemical which will require different set of instructions as opposed to the common photo resist in the lab.
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Week 9

We decided to take a break from doing our fyp. This is to allow ample time to study for the upcoming mid semester tests and rest during the holidays.

Week 10

MID SEMESTER TESTS
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10 June 2008

Objectives

We have written an experimental procedure of the PIV system earlier in the week. As Hariz missed the first part of the training, we decided to run the experiment again with our own experimental procedures and Hariz doing it from the start. Also, we wanted to see how the differential pressure between the two inlets will affect the liquid flow in the liquid.

What was done

As we were the pilot research group for this experiment, we were asked to write down a list on procedures by our supervisor Mr. Ting. This is to act as a reference for the future FYP groups that will be doing this experiment and also enable us to do the experiment without any doubts. So as to ensure that the experimental procedures are user-friendly, Hariz was tasked to run the whole experiment by just referring to the experimental procedures.

Our experimental procedures are still subjected to changes. After more feedback from our project supervisor, we will amend it.

For the differential pressure, we decided to try out how the difference in height of the 2 inlet syringes affects the way the fluid flow. By having a difference in the height between the syringes, it creates a differential pressure. Initially we thought that the speed of the higher placed syringe would travel much faster then the lower placed syringe. But after seeing the results from the software, we found out that the liquid flow in the channel within the chip was turbulent as the vectors calculated by the software were all over the place. It also shows some mixing.

We also noticed a particular pattern from the few runs that we conducted is that there is a vacuum effect at the junction where the 2 streams meets, this vacuum effect causes some of the liquid to flow to the lower positioned inlet syringe.

Another pattern we found out is, there is some circular patterns from the vectors after the junction. We conclude that there is mixing occurring at these circular patterns and it continues mixing due to the incoming stream of fluid.

Problems

We are unable to testify fully that the circular patterns plotted out by the software pattern are mixing as we made a mistake by starting with a high differential height between the 2 syringes.
For the vacuum created, we are only able to conduct a firm conclusion when we have tested with various differential heights.

Solution

To solve the above problems, we are going to start of with a minimal differential height to the differential height we did this week. By doing this, we are able to see the pattern on each stage conducted, thus, concluding into a firm statement.

Conclusion

This week’s experiment on the differential height will give us a firm foundation on the topic mixing for micro fluidics. Though the lesson we learnt today is based on gravity creating a differential pressure, we are able to learn the basic foundation of how fluid flows in such condition. By having this foundation knowledge, we are able to proceed into a more challenging task for pressure driven by using 2 syringe pumps, both at different speeds.
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leaving the glass pieces to dry

the spin coat resistor machine

coating the glass piece with photo resist

soft baking the glass pieces the UV ray machine
imprinting the design desired for the glass piece
soaking into for the first bath
checking for any abnormalities after the imprinting
followed by the second bath
the last bath before being dried

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30 May 2008 & 6 June 2008

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23 May 2008

What have we done?

We plan out what are we going to do in the following weeks of our project, how is suppose to go according to our plan with extra time for unforeseen circumstances.
We also went to research out on what equipments are needed for doing our experiment especially for electric driven micro fluidics as the equipments needed is different than the one being used by pressure driven.
We also went to research on various fields that will affect our results and data like viscosity, two inlets both at different speeds.
In conclusion, this week allows ample time to regroup our initial plans that we had and had more concrete ideas on our project research.

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9 May 2008 & 16 May 2008

Purpose of Carrying Out Fabrication of Biochip Practical

The purpose of doing this practical is basically to prepare us for our Final Year Project (FYP). This practical gives us the fundamental understanding on how to manufacture a micro-channel in a chip which is going to be used for our FYP. Due to this understanding, we can now be able to create flow channels in the chip to study closely on how the fluid particles flow within these small channels on various patterns which we are interested in.

What have we learnt?

We learnt how to use the various machines which were useful for our project ahead. By doing this we also get to know why is each step important, what does each step does and how it works, from cutting a piece of glass to cleaning the glass with numerous chemicals, coating the glass pieces with photo-resist to using Ultra-violet light to imprint a pattern on the glass microchip and cleanse it to produce the final product.

What difficulties we encountered

When handling the glass pieces for cleaning and other procedures, we encountered some problems of handling the glass pieces using a pincer as it was quite difficult to grip the glass especially when it was wet

Conclusion

In conclusion, we have learnt that patience and accuracy are the two most important points in doing this practical as every procedures is crucial as a small mistake in any process can ruin the whole chip or it may cause some chemical residues to be left on the glass causing the product to be defective. When doing the actual micro channel, the procedures may vary according to the TSO, but by we were still able to grasp hold of the finer details in making a mircro channel.

Credits

Mr Goh, TSO of the nano frabrication lab in T12a, for helping us and guiding us throughout the whole experiment and the start of our project

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CCD Camera, Progressive Scan
• A charge-coupled device (CCD) is an analog shift register, enabling analog signals (electric charges) to be transported through successive stages (capacitors) controlled by a clock signal.
• Progressive scanning is a method for displaying, storing or transmitting moving images in which all the lines of each frame are drawn in sequence.
• Interlace is a technique of improving the picture quality of a video signal primarily on Cathode Ray Tube (CRT) devices without consuming extra bandwidth.
• Interlacing causes problems on common display devices such as LCDs.

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