The posts on this page are in chronological order, with the most recent appearing at the top whilst the earliest dated posts are to the bottom of the page.
In the month of August
9 Aug 2018 – Day 3 of 6 Aug Bacteria Batch:
The bacteria as shown has continued to grow and is concentrated on one side, presenting a dark pale yellow colour.
The bacteria has grown to be to more visible on one side of the petri dish, presenting a light pale yellow colour.
From the above results, we can tell that the control agar developed a denser layer of bacteria, whereas the plasma-treated agar developed a weaker layer of bacteria.
8 Aug 2018 – Day 2 of 6 Aug Bacteria Batch:
Bacteria is now visible and presents a light pale yellow colour.
Bacteria growth is hardly visible, but some traces can be seen.
7 Aug 2018 – Day 1 of 6 Aug Bacteria Batch:
Of all the 3 different batches we made on 6 Aug, the milk agar batch showed the most obvious growth. Hence, we are using samples from the milk agar batch.
Keyboard Bacteria – Milk Sample – Control; Day 1:
There is no visible bacteria growth yet.
Keyboard bacteria – Milk Sample – Plasma-treated 2 min; Day 1
There is no visible bacteria growth yet.
6 Aug 2018 – New Batch of Petri Dish Samples:
Some time ago we mentioned that the beef stock we used was not entirely appropriate for our experiment. Today we decided to create a batch of agar replacing beef with milk. After this we searched online and confirmed that milk agar does exist in culturing bacteria samples. Satisfied, we proceeded with the experiment.
Because we previously used bacteria monocultures from yoghurt, the resulting colonies that grew were of only one color and it was hard to tell. We decided to try to grow a variety of cultures and hence thought of swabbing a computer keyboard on one of our laptop computers. In case this didn’t work, we wanted to have a backup which using bacteria from the fingers.
Following our plans, these are the bacteria samples on Day 0 of their conception:
Left column T to B: KB (Keyboard swab) – B (Beef stock medium) – Control; KB – B – 2 minutes exposure to cold plasma flame; KB – B – 5 minutes exposure.
Middle column T to B: Finger bacteria – Beef stock medium – Control; Finger bacteria – Beef stock medium – 2 minutes exposure time to cold plasma flame; Finger Bacteria – Beef Stock Medium – 5 min exposure.
Right column T to B: Finger bacteria – Milk medium – Control; F – M – 2 minutes exposure; F – M – 5 minutes exposure.
3 Aug 2018 – Results of the Petri Dish Experiment:
Here are the results of the petri dish experiment.
Plasma Treated Bacteria:
A white film has formed over approximately 1/5th of the agar.
Control:
A white film has formed across more than half of the control agar.
From these results, it seems that plasma has the potential to eradicate bacteria in the absence of a tightly controlled research environment. However, in order to confirm the reliability of such results we need to conduct more tests. Hence we will be filling out more samples at the lab.
2 Aug 2018 :
Today we tried to use the final design printed parts. We had 2 different designs. However with both designs, it feels like a mild electric shock when the finger is placed at the cold plasma location.
We expect that the failure is due to the soldering problems, the aluminium foil ground not being connected sufficiently securely to the wire. Perhaps the exposed ground copper wires emerging from the insulating tube is not By checking using a multimeter, Dr Rainer and us realized the bronze copper wire we’ve been using for the live wire coil is actually insulated everywhere except the wire tip. Hence, we are planning on stripping a thin insulated wire to ensure that the coiled wire is truly live over all its exposed surface area, to ensure that the gas comes into contact with more surface area of the high voltage coil and thus more positive helium gas ions will be produced. Hence, we expect that this was the reason for the sparky prickly feeling we got when putting our finger over the plasma flame; not enough heavy ions, and so more electrons are present concurrently at different regions, hence flowing through the finger at different points of the skin at different times (hence it feels like prickly small shocks that last momentarily in one area but the occurrence of such shocks are continuous). Large enough electrons flowing for it to be registered by the brain as a shock. One reason for feeling the mild electric shocks is that the shoes we are wearing do not have rubber soles that are sufficiently thick.
So we are resoldering the parts to give a more safe design.
1 Aug 2018 – Improving the Final Product Design:
The improvements we made were: Adding an additional part at the back for stabilization of the gas flow tube; prior to this it was very forceful and stubborn against use in our setup, and disrupted our setup many times when it left the gas flow inlet area, because it was originally curled up against the gas tank and so it would retract into a more similar shape quite easily. To combat this, we designed an additional part that would place more weight on the end where our setup is, so it can provide a torque that helps secure the position of the gas flow tube.
We made two products of different colors.
In the month of July
31 July 2018 – Finding out the Flow Rate Specification, and More Batches of Agar:
For the purposes of improving our plasma experiment, we are cooking the agar which will house the bacteria the plasma will attack and plans to modify the solution are as follows:
Make 2 batches of agar, each enough for filling 3 petri dishes. 1st batch will be no-beef-stock, instead replaced by sugar. 2nd batch will be with lesser beef stock than yesterday, perhaps only a few slivers.
Here is a video of us making the agar solution. We added 1.5 teaspoons of beef stock extract, 1.5 teaspoons of sugar, to 1.5 cups of water.
We realized instead of placing the petri dishes from yesterday into the air-conditioned room, we ought to store it in a much warmer area for the bacteria to grow sufficiently. Hence, we are planning on placing the petri dishes near a fridge, where the external cooling system will give off heat generated from the fridge, and hopefully the heat will sufficiently quicken the bacteria growth in the petri dishes.
Today, another eureka moment was when we agreed on a non-expensive solution (not needing any extra equipment like the manometer or pitot tube we mentioned here 2 weeks ago that we found online) to measure the flow rate of the helium gas we have been using from the Making and Tinkering lab.
Here is a picture of our design. 
With improved details:
These are videos of us conducting the actual experiment for calculating flow rate of helium that we use:
At our initial flow setting, the helium flow was too fast and for a 500 ml beaker, the beaker was filled up with air within 2-3 seconds such that we could not accurately ascertain the time at which the water level in the beaker reached the 500 ml mark. Hence, as a rough estimate, we lowered the flow of the gas to a speed lower than what it is usually until we were able to measure it. The good news is we sometimes also use such a low flow speed when starting out, and cold plasma can be observed coming out of the nozzle even at lower speed – just with less intense observable color. Given more time we would have liked to purchase a gas flow meter to measure the flow rate at higher flow speeds. However, this was the best we had with the time limit. We conducted the experiment multiple times to get an average time interval.
Since we timed an average of 7 seconds for 500 ml (0.5 litres) of water to be displaced by the incoming flow of gas from the helium gas tube, that gives a flow rate of 3.75 litres per minute.
Hence, this is the flow rate specification for our device.
30 July 2018 – Update
Okay. So we failed. But it’s not a crippling failure. And we intend to right it. We think it’s important to be open about these things, and let them be stepping stones rather than hindrances to our success.
So we were creating samples for testing how effectively our plasma pen can combat bacterial growth. And, we used a recipe from online. This recipe included beef stock – so we went and got some household beef stock. The problem with this is that the stock was very oily; it contained beef fat and was not powder at all, which the recipe called for one teaspoon of. So, we probably put in a lot more beef stock than necessary. To be fair, we were worried about contaminating the sample. We should have been careful and more thorough with ensuring we pushed the beef stock down into the teaspoon, melding it into a dense block in the teaspoon rather than roughly estimating the amount just by looking at it from the top and leaving lots of large air gaps in between the occasional blobs. The result? Because there was too much beef stock in the agar solution we concocted, the solution ended up being full of salt, which could potentially inhibit the bacteria growth we need to attack with cold plasma. There was also evidence of there being too much beef stock from the conspicuous white film of coagulated fat that gathered largely above the agar layer. But that wasn’t the only setback.
We also failed to regulate the amount of yoghurt we put in. We should have diluted the yoghurt a little into a less viscous solution, and then done it in a spread-out zig-zag fashion only once per petri dish.
So here’s some pictures of our attempt.
We are going to repeat the experiment again, with new dishes. We’ll keep these and observe how bacteria grows on each of these in the meantime.
27 July 2018 – Dr. Rainer Tests Out Our Plasma Pen. Plasma Calamus: First Final-Design Success
We assembled our 3D-printed Plasma Calamus parts for the first time today. This design is improved from yesterday; we made new 3D printed parts that fit even better.
A few days ago, Dr Rainer and us discussed some final milestones, and this which you see in the video is already 90% of the first final milestone: to have a 3D-printed construction in which to encase our “pen” – electrodes, glass tube and all – so it’s safer for a user to pick up with one’s hand. In this video, you can see the pen which finally fits into each other and looks the most aesthetically professional it has ever been.
While in this video, we had not picked up the pen yet, we asked Dr Rainer whether in his esteemed opinion it is safe for us to start to do so. Since Dr Rainer does work with plasma, and is our Principal Investigator, we thought it good to consult him on safety issues prior to chancing any injuries or fatalities. We did not wish to throw caution to the winds.
After consulting with Dr Rainer, we came up with the following amendments to our design:
- Made the inlet for gas flow tube deeper so the tube for gas inflow is more secure.
- Place the two thin wires connected to the electrodes into one bigger insulating wire, so that the finished product (Plasma Calamus) looks increasedly professional.
We also want to create agar to test the efficacy of plasma in inhibiting bacterial growth.
Basically, we are jumping straight into the 3rd Remaining Milestone we aim to hit with the remaining time left for this project.
After receiving 3 petri dishes and agar powder from Dr Rainer’s lab, we found a recipe online from to help us with making nutrient-containing agar solution. We’re excited to conduct the experiment and test out the potential plasma has in inducing bacterial apoptosis (apoptosis : scientific name for cell death).
(Taken from https://tinyurl.com/ya5ppeyj)
Meanwhile, we excitedly called Dr Rainer in to have a look at our apparatus today. He actually tried holding it with his hand! And the verdict went well.
Dr Rainer tests our Plasma Pen:
And thankfully, he pronounced our design safe. This means we have finally reached our goal as listed on our 23rd July post. He also taught us how to safely hold the plasma pen for added measure. We’ll divulge this great secret to you soon. So stay tuned.
26 July 2018:
We made minor amendments to the dimensions of our prototype. The hole for the glass tube in the boot was too large and so we made it smaller. We also printed the body in white. We changed the inner diameter of the body so that the glass tube can fit in the body better.
We also conducted the experiment. It looks like our best yet. Here’s a video below.
However, the parts are loose and do not join together. This means the configuration is not completely safe, since electrical discharge could occur in between the gaps. It also does not look very professional even if we were to glue it together. We will fix this soon by altering our 3D-designs.
23 July 2018 :
So last week we succeeded in creating a prototype that emits non-thermal plasma from the nozzle outlet. This was replicated with various design configurations this morning: Namely, the boot vs the tube wire-collector.
However, this morning, after consulting our Principal Investigator, Professor Rainer Dumke , we decided to first focus on creating a well-insulated plasma calamus design that can safely be held without the risk of electrocution. When that is done, we then plan to get the electrical specifications of our device (such as voltage, current), and as well as the gas flow rate required. To this end, we aim to either purchase or make a glas flow meter. Recent searches online have shown that either the delivery time is too long or the item is unreasonably expensive (speaking in the range of hundreds to thousands of dollars). However, upon slightly further research, it was unearthed that there could be a potentially more affordable idea for measuring gas flow velocity – construction of a pitot tube, a device that measures pressure with respect to a static pressure point (a manometer of sorts). Afterwards there is an equation to obtain velocity in metres per second.
NOTES FROM MEETING: REMAINING MILESTONES
1st- Get a working prototype one can pick up with one’s hands
round 3d printed part in the front to prevent arcing
3d body for the entire setup
2nd- Get the specifications of our device (the output voltage, current flowing through our circuit – Kum Yin will pioneer and we will check the design mathematically, then experimentally, gas flow meter – Bryan and Shuhui will go back and think about how to do it)
A potentially more affordable idea for measuring gas flow velocity is a pitot tube. make a manometer.
3rd- Test on Petri dish with droplets of milk (milk bacteria). Petri dishes and agar jelly from Dr Rainer’s lab
We had been pursing two different 3D-printed designs to be placed at the end of the glass tube.
However, we decided that the boot design is preferred such that all the wires are away from the body of the plasma pen.
20 July 2018:
Today we tested the use of laminar flow and turbulent flow. We found that there is not much difference in the non-thermal plasma flame produced via the two different gas flow methods.
Thus, after trying the abovementioned experiment, today we also began to use a glass tube as our dielectric between the cathode straight wire and the anode aluminium foil – in place of the previous aquarium rubber tubing which is smaller in diameter at about 5 mm. At first we just used the glass tube without any nozzle at the outlet end. Because the diameter of the glass tube is at 10mm, it is too large and the resulting plasma flame emitted is very dispersed. Hence the camera could not capture it, although we could see the flame faintly with our naked eye.
We tried using a plastic pen body over the rubber tubing. We have found out a few days ago that without fail, the rubber we are using (old fish aquarium rubber tubing) will break down at high voltages as the breakdown voltage is not high enough to withstand. Hence, we were thinking of getting a tube open at both ends of higher breakdown voltage than that old plastic. So remember yesterday we talked about thinking of glass tubes instead of plastic/rubber tubes? We sourced for glass tubes. We obtained two tubes as of today:
Marcus gave us his glass straws when he heard we were looking for glass tubes. We commend him for his helpfulness and have put his name in the credits section in our final powerpoint presentation.
The good thing about glass, as we mentioned last post, is that its breakdown voltage is much – much – higher than the plastic/rubber that we’ve been using.
Well, we tested the setup out using the newly obtained glass straws. We did the experiment with a coil of wire as the live wire electrode, to maximize exposure of the gas to a stronger electric field. This was the result:
We also tried it with a longer nozzle to investigate the effect:
Next, we tested how the cold plasma flame feels again. It felt, in all, like a flow of cool air. However, sometimes it felt a pit prickly.
19 July 2o18 – We Try Placing Our Hands in Front of the Plasma Flame
Here it is:
The cold plasma flame, while not only failing to burn paper or be of sufficient heat to cause thermal paper to react, can also be applied onto the hand and it felt cool to the touch.
After this exciting discovery, we then test using different distances from the nozzle tip (the tip of the dielectric tube).
2cm gap from nozzle end to left side of aluminium foil electrode:
The rubber tubing we use here is the same kind used to supply oxygen to fish in aquariums. We snipped some of it from a whole coil of tube, and this tube is open at both ends allowing for gas to enter in one opening and exit from the other. The flame is curved because of the curved nature of the clear rubber tubing, which is the dielectric in our setup. This means that the location of the tip of the cold plasma flame is not as predictable, since it flickers as seen in the video, which is exacerbated by the curving of the flame. To fix the problem, we resolved to get a straight dielectric.
Towards the end of the video above, you would have noticed a sudden small “explosion” with smoke indicating the presence of hot plasma all of a sudden. When the knob on the DC supply was turned beyond half, the rubber tubing breaks down (the voltage has reached its breakdown voltage) and the gas ions pass through the tube towards the aluminium foil ground electrode. We also want to fix this problem of too low a breakdown voltage of the dielectric material we’re using. We are thinking of glass, for it has a higher breakdown voltage. With regards to the earlier problem, it is also much more rigid and geometrically it is straight – fitting what we need to get a strong jet which is our focus at the moment. We are sourcing for such a glass tube, open at each end, with immediate effect.
18 July 2018 – Our Thermal Paper Test
We made a thermal paper test.
As seen online, in the presence of thermal heat will a piece of thermal paper react by darkening:
(taken from https://en.wikipedia.org/wiki/Thermal_paper)
When compared to placing our receipt in the flame, it certainly shows that no heat was present.
More experiments to follow, such as putting our hand in front of the flame.
Final Design
We created this diagram explaining the electrode configuration and materials we are using for plasma production in our final design.
The coil is such that gas atoms come into contact with a larger surface area of the high-voltage coil. Hence, the electrons have a larger surface area at which to “escape” through the live copper wire. This will ensure that, after the drop in potential is registered by the gas at the region enclosed by the ground electrode and some electrons and ions recombine, that significantly more heavier (and thus, lower-energy, and hence colder) ions are present than high-energy (and thus, hotter) electrons. Thus when one places one’s finger at the outlet, the gas will feel colder.
Why coil is at the front and not at the back of the tube: To prevent the positive gas ions from recombining in the middle of the glass tube. Hence if the most gas ions are formed closer to the ground electrode, there are much more heavy positive ions that are emitted, enshrouding a disproportionately smaller number of electrons, and hence this ensures the plasma produced is much more “cold” than thermal.
4 July 2018 – Stars and Stripes – For the First Time Ever, We Produce Cold Plasma!
Not only was 4th of July a cause to celebrate in America – so was it a day of celebration for us here in Singapore. (July 4th is America’s Independence Day)
We found a purple ion discharge between a dielectric and the aluminium foil ground electrode we were using. We used aluminium foil as the positive electrode as well, pasted onto a black rubber casing and placed a few millimeters away. We used a glass plate as the dielectric barrier.
Here’s another one:
And at last, the long-awaited result of the thermal paper test:
As seen in the video above, the newspaper did not burn as is in the case when lightning strikes a grounded object.
3 July 2018:
Today heralded an air of uncertainty: Was that which we saw for the first time… non-thermal, or thermal plasma? In the video below, you’ll see just a few brief seconds of discharge.
In the month of June:
Special Term I Week 7:
We tested our circuit using the plastic prototypes we had printed in Week 3 and Week 4. We also printed more plastic prototypes for testing with the flyback transformer circuit.
We also finally got the DC supply Dr Rainer recommended us to get this week! We connected it to our flyback transformer and continued testing.
However, after turning the voltage setting on the power source higher and higher, at a certain point we realized that electrical arching was occuring between the voltage pins on the back of the flyback transformer. The 4th pin was emitting some electrical discharge that arched onto the 5th pin. Hence you can see the charred black bottom of the 5th pin; damage done from the thermal discharge.
After a few experiments with similar results (the flyback pins would not stop arching), and upon consultation with Dr Rainer, we realized we needed to identify the ground pin. We used a multimeter probe to check between pins and found the 5th pin to be the ground pin, which made sense that discharge from a higher pin (4th pin) occurred towards the 5th pin.
Upon repeated usage, we had to go to increasingly higher powers to get discharge between two wires (one high voltage wire and one ground wire) connected to the circuit. A sample of how we did the experiments for physically testing the flyback circuit is here:
Special Term I Week 6:
We finally have everything ready to test out our circuit!
Setting up was fun:
with the formidable power source we got from Dr Ranjani, courtesy of the Year 1 Physics Lab
Okay, now the all-the-more fun (should I say dangerous.) part! We are finally going to see if it works! Be careful. It might burn through the screen.
So a thermal plasma was produced! Look at that pretty bluish-purple corona discharge, also known as an electrical arc. Arcs can be pretty dangerous, especially if they overcome the dielectric barrier and arc onto the human body – if it’s in more favorable proximity than that wire (which has not been grounded yet at this point! Well what can we say? Literally, we are almost giving our lives for this project 🙂 We’re lucky we didn’t step too close). Perfect! We just wanted to make sure our circuit actually works. And, as you can see from the video, it does! Discharge occurs.
So now we’re going to try it with our designs which were based off of actual designs made by researchers who tried to produce cold plasma.
Progress of project for Special Term I week 5
We researched on soldering. Tried to determine whether we should solder onto the wood. We aimed for the physical connection of the wires. We also tested the mosfats, source drain gate: Results were not very conclusive. Concurrently, we were also considering other sources of voltage such as AC voltage source, versus the pulsed DC voltage source as well as the steady DC voltage source.
Started soldering wires on the perf board we’d gotten earlier to connect the flyback transformer Tin gave us.
We also ordered the steady DC voltage source supply on AliExpress online.
Progress of project for Special Term I week 4
We continued printing the parts for our prototype. We continued buying parts from hardware stores in Singapore based on the circuit diagram.
We also did more research on the plasma pens available and read research articles on applications for plasma technology.
Progress of project for Special Term I week 3
Tin gave us his flyback transformer. We worked on the setup of the circuit. Went and got new circuit components due to following a new circuit diagram that was “neater”, at the request of Dr Rainer.
Image of circuit from instructables
Progress of project for week 2
23 May 2018
Notes on the calculation of current from P=VI:
Flyback transformer – convert DC to AC. We will calculate the power input and get the power output which will be the P that we substitute into the equation
Shuhui will do a design on rings
Questions to ask Dr Ho:
- Approval for buying flyback transformer, Arduino uno/mega (555 chip with capacitor)
- Do we need to record the number of hours in the log book (secretary)
- Our Stream
Progress of project for week 1
Minutes.
15 May 2018
Discovered on a paper that a plasma device used in research paper utilized kilohertz and Megahertz frequencies. How to generate such high frequencies??? Power generator in Y1 physics lab? Asked Dr Ranjani (Y1 Lab Manager)- max frequency available on signal generators: 10 kHz.
16 May 2018
Plasma Pencil:
Composition – 2 metal plates, hole in the centre through which air passes through
Consultation with Dr Amir: What are the parameters? The physics behind it?
Compressed gas (from a pump) through the device, passes through the high voltage AC plate, reaches the grounded plate.
Air flow (fluid dynamics), plasma(ionization), electric current (AC) —-
Find the best example of all the modules we need that can build our situation, get the trial version from COMSOL Singapore of Plasma physics. Plasma module works, but any others?
We found various model application files on COMSOL website related to physics principles we are using. The component Plasma (plas) was used in one Corona Discharge example. However we are using an 2D Axi-Symmetric Domain. Conclusion: We need to have all the modules we are using so that we can apply it on the correct (axial symmetric) domain to get our final.
Dr Amir commissioned us to find more examples of using the applicable physics modules.
Power generator–Use Arbitrary Waveform Generator from Y2 Lab. Permission asked 15 May 2018 and granted. It was agreed that Y2 Lab Manager Aun Mee should be present whenever we use the device in the lab.
How to connect power generator to our plasma pencil? – Borrow BNC cable, connector and crocodile clips from Y2 Lab. Permission not yet asked.
Dielectric Barrier: 3d printed plastic is our first choice
Thursday, 17 May
Met with our assigned professor, Dr Rainer Dumke, at his lab. He suggested we use a DC circuit and prepare following before our next meeting:
- Risk Assessment
- Get a rough calculation of the current that should be flowing through our circuit
- Get a rough calculation of the estimated frequency (using current and capacitance quantities)
- Make a rough design
- Identify the design parameters