Abdullah Irfan

Week Activity 1 Started reading up on confocal microscopy. The following page was particularly useful: http://www.physics.emory.edu/faculty/weeks//confocal/. Made new (more concentrated) microsphere solutions to collect better data and got more accurate results. As far as the new direction of this work is concerned, I narowed down my work to two fundamental problems that I must solve. Firstly, I need to develop a proper treatment of bidisperse solutions. Secondly, I need to develop a treatment for drifting particles. This second problem involves two approaches according to my current understanding. I need to see whether I have to fit the curve to the appropriate function to find the velocity or if I can extract enough information from the decorrelation time of the process. 2 Did a thorough literature review while looking for details about particles drifting in the liquid, and about bidisperse suspensions. The following paper helped understand what I should expect from the analysis of a bidisperse colloidal solution: "Differential dynamic microscopy of bidisperse colloidal suspensions" by Mohammad S. Safari, Ryan Poling-Skutvik, Peter G. Vekilov and Jacinta C. Conrad. If I want to clearly observe two distinct plateau, the size of the larger particles must be atleast ten times greater than the smaller ones.The following paper has turned out to be very useful in two different ways: "Differential Dynamic Microscopy: A High-Throughput Method for Characterizing the Motility of Microorganisms" by Vincent A. Martinez, Rut Besseling, Ottavio A. Croze, Julien Tailleur, Mathias Reufer, Jana Schwarz-Linek, Laurence G. Wilson, Martin A. Bees, and Wilson C. K. Poon. Firstly, it includes diagrama and descriptions that illustrate the difference in the curves for diffusing and drifting particles. Secondly, it neatly describes a method to estimate the fitting paramters, A(q) and B(q), allowing us to isolate and plot f(q, delta t), which then allows us to study how it decays as a function of lag time. The number of decays in this plot tells us how many decorrelation mechanisms are at play (for example a drifting and diffusing system would show two decay mechanisms). 3 Following the method used to estimate A(q) and B(q) by finding D at low and high delta t, I isolated the decorrelation functions. Although the decorrelation drifting spheres did show faster decorrelation than the diffusiing spheres, neither of the functions were decaying to zero. I believe that because the low frame rate of the video results in there being no plateau in D at low t, our estimation of B(q) is very poor, therefore, the estimation of A(q) must also be poor. I have returned to fitting the functions and calculating the paraemters. After this, when I plot the decorrelation functions, the show the trend that I expect, and they decay all the way to zero. 4 I have been working on fitting the curves for drifting spheres to the appropriate function, and the task turned out to be more difficult than I had imagined. I am now trying to fit using Mathematica, since MATLAB has been difficult to use for a complicating fitting model. Apart from that, I wrote a small program that will help me simulate the correlation functions fro diffusing and drifitng spheres, allowing me to see how the function should behave according to the percentage of spheres that are moving with a certain velocity. Update: The fitting program finally worked. I will now look at the fitting parameters to extract the velocity distribution of the particles. Update: Despite the fact that the fitting seemed to be pretty decent, the parameters are not making much sense. Most of the values for the decay time of the diffusive motion are negative. The constants related to the velocity distribution of the particles are varying a lot, while we expect them to remain constant. Wilberforce Analysis: I have made a program that simulates the motion of both coupled pendulums using the initial conditions. I will generalize it to 4 degrees of freedom on Monday morning. 5 It turns out that although MATLAB was fitting the curves, the fitting wasnt good enough. I removed the data that seemed to be unnesecary from the extended regions of the curves, and retained only the region uptil the beginning of the plateaus. The fitting drastically imporved and the parameters started to make sense. The percentage of drifting particles, alpha, varied close to 1, which is correct since the entire system was flowing. The camera noise term is still not constant (this has been a problem since this work started). The average velocity came out to be around 2.9um/s. I opened the video in ImageJ and manually estimated the velocity of several randomly chosen particles. These velocities varied between 2.3 and 3.1um/s, which makes me think that the estimate was pretty decent. I will now repeat the experiment with particles moving at a different velocity in order to make sure that these results really are the result of a proper implementation of this technique, and that I wasn't simply lucky. Moreover, i analyzed a video i had recorded a few months ago. I kept the relolution very low in order to get to 50 fps. The problem is that the curves were not smooth. My guess is that the small number of particles is the problem. I will now repeat this with a much more concentrated solution and try to see how much results could improve if i could work with a 50 fps video insetad of a 20 fps one. 6 I have realized how the fitting routine should work: 1. I identify the range of accessible frequencies. I am currently sticking to curves 60 to 160 since these curves gave time constants for Brownian motion that agreed well with the theoretical values. 2. Next, I move on to the batch-fitting program. In order to give it a good initial guess for the parameters, I open the first curve (curve 60) in Mathematica, and attempt to manually fit it to the appropriate function. I then use those parameters as the guess for my batch-fitting program on MATLAB. The program automatically updates the guess parameter as it moves on to the next curve. It turns out that this fitting routine works well for curves 60 to 110. I use the fitting parameters to estimate the average velocity of the particles. I then open the video in ImageJ, and manually track random particles over a few seconds in order to estuimate their velocities. I estimate the average velocity and compare it to the one obtained using fitting in MATLAB. The latest data I collected showed these results: Fitting -> 1.7 um/s, Manual estimation -> 1.66 um/s. Remaining issues: The value of alpha (the fraction of particles in motion) turned out to be 1.45 for the data set mentioned above, which is certainly not good enough. The variation in the velocity that the fitting parameters give is way too small. Next steps: 1. These remaining fitting issues need to be fixed so that all the parameters make physical sense. 2. I should try DDM with different sized particles. 7 I spent some time going over the work I had been doing before the lockdown. I regenerated the curves that I was working on to get familiar with the fitting routine again. I listed down the important points that I will mention in the report. Unfortunately, there are not too many conclusions I can make from the current analysis. However, I will describe in great detail the process that I brought me to this point and the next immediate problems that need to be solved. Although there is a major issue with one of the three fitting parameters of the velocity autocorelation function, I am confident that the parameter that gives us the average velocity is pretty close to the actual average velocity of the particles. However, before including this conclusion in the report, I need to look into one more decent data set that I have and see if I can also estimate its velocity upto a reasonable accuracy. 8 9 10 11 12 13 14

Usman Baig

Week Activity 1 Read the following texts to understand the physics behnid the phenomenon of 'Surface Plasmon Resonance': 1. Principles of Nano-Optics by Lukas Novotny and Bert Hecht (Chapter 12) 2. Fundamentals of Photonics by B. E. A. Saleh and M. C. Teich (Chapter 5 and 6) 3. Solid State Physics by Neil Ashcroft (Chapter 1) Through these readings, I understood the Drude Model and how it can be used to explain mathematically, the depedence of Perimitivitty, Propogation constant and Refractive Index of a medium on the frequency and how the concept of a plasmon frequency naturally arises from the model's mathematics. Furthermore, I realized why we do not commonly encounter surface plasmons when light is incident through air(acting as a dielectric) on a metal and therefore learned why the experimental setups such as the Otto and Kretschmann configurations exist. 2 Read the following texts to understand the implementation of the principles behind 'Surface Plasmon Resonance' in a laboratory experiment: 1. Laboratory experiments for exploring the surface plasmon resonance by Olivier Pluchery, Romain Vayron and Kha-Man Van 2. Angular Interrogation of Surface Plasmon Resonance by Hassaan Majeed, Junaid Alam and Muhammad Sabieh Anwar Understood the working procedure behind the experimental setup that I am hoping to improve upon. Also, as per Dr. Sabieh's instructions, I met and talked with Eng. Hassaan about the experimental setup that already exists in Physlab 2. The current setup has mechanical limitations whereby the angle through which we can move the incident beam is very constrained. I need to work out a way to significantly enlarge the range of angles for which the setup can work. 3 No practical progress this week. I was injured so could not go to the lab. Could not meet Dr. Sabieh as either he was busy when I had time or I had classes when he was free. 4 Met with Dr. Sabieh to discuss how to proceed forwards with the experiment. Afterwards, discussed the working of the experimental setup with Eng. Hassaan. Had a misunderstanding about the derivation of the formula for converting the measured exterior angle to the interior angle, against which we have to plot the reflection intensity. Spent about an hour and a half explicitly deriving the main formula and correcting this misunderstanding with Akbar Ali. Took three sets of readings and plotted the results. The general shape of the curve corresponds to the theoretical shape the graph should have but the value of the internal angle at which extinction should occur is off by about 15 degrees. Tried to work out the reason for this discrepancy and came up with two possible sources of error: 1) Measured angles not equal to their perceived values 2) Problems with the collimation and polarization of the laser The program used to control the experimental setup only allows discreet steps of minumum one degree for the rotational stage. There is no information marked on the motors to asses whether this is actually the case i.e. when the program is used to move the stage by one degree, is the resulting rotation actually of one degree? I thought about this possible limitation for some time and then divised a rather crude but simple method to check this. I made a small horizontal mark on the stage and suspended a ruler vertically using a retort stand in such a way that its edge coincided with the mark. I then used the program to rotate the stage 360 degrees and then checked to see if the mark I had made again coincided with the ruler's edge and found that it more or less did. I concluded from this that the error between the actual value of rotation and the ideal value cannot be the primary reason for the faulty measurement of the angle at which extinction occurs. I will work on the second assumed reason on Monday along with trying to explore other reasons. I recieved extensive data and results related to this experiment from Dr. Sabieh and reviewed them. Dr. Sabieh had asked me to prepare a shopping list of the instruments needed to produce a collimated laser beam so it could be used in the present experiment and others in the Physlab. I searched them on the web and selected 3 laser diodes, 2 aspheric lenses and a mount and submitted the list to him. 5 Prepared the Shopping List sir had asked me to to prepare. Selected three laser diodes and two mounted aspheric lenses which fit the specifications we were looking for. Also selected a mount to go with the laser diodes and the aspheric lenses. The mount turned out to be too expensive and I have to to look for a cheaper option now. The combination of the the diodes and the lenses would give us a collimated beam radius of around 0.28mm which is much less than any I could find for commercially available on the internet. The links to the selected instruments are listed at the end. To rebuild the experiment, I got a 10 nm gold-coated glass slide cut and used an index matching fluid to pair the slide with the prism to be used in the experiment. The slides were not kept in the container in the correct way so there was no way to determine which side had been coated and which side was not so I examined the slide and guessed which side was coated. I then left the prism to dry and then used it to get a dataset but the data did not show the typical SPR Curve. Since the index matching fluid had already been apllied to to one side of this slide and it was not giving correct results, I got another slide from another conatiner on which it was labelled which side was coated and which side was not. Cutting up the slide required delicacy so I asked Hafiz Sahab to cut it and explicitly asked him to keep track of the coated side. He was busy at the time so told me he would do it and place the cut up slide at my workstation. I then got busy working on the aforementioned shopping list and had to leave the lab for a little while. When I came back, the cut -up slide was at my workstation so I assumed Hafiz Sb had kept track of the coated side and had placed the slide with that side upwards(as I ahd asked). I applied the index-matching fluid and got another dataset which again did not show any typical SPR behaviour. Later, Hafiz Sb told me he ahd lost track of the coated side while cutting and so had guessed while placing the slide on my workstation. I have to work out why my datset is not giving me the correct values and the correct curve? Is it due to the wrong setup or are the values of the angles I am taking the readings for wrong? List: Laser Diodes: 1)https://www.thorlabs.com/thorproduct.cfm?partnumber=L515A1(515 nm) 2)https://www.thorlabs.com/thorproduct.cfm?partnumber=HL6358MG(639 nm) 3)https://www.thorlabs.com/thorproduct.cfm?partnumber=HL6748MG(670 nm) Mounted Lenses: 1)https://www.thorlabs.com/thorproduct.cfm?partnumber=C140TMD-A(1.45 mm) 2)https://www.thorlabs.com/thorproduct.cfm?partnumber=C710TMD-A(1.49 mm) 6 Had a meeting with Dr. Sabieh where we discussed the the instruments I had suggested for collimation purposes. Along with the laser diodes and the aspheric lenses, we needed a collimation tube which could either be built part by part or bought commercially. The commerially available tubes have the disadvantage that we will have to use the lenses that come pre-fiited in the tube so the radius of the collimated beam would increase from 0.28mm to around 0.8mm. Dr. Sabieh said this was acceptable so I looked up the collimation tubes that fit our needs. We then went to the store to check which of the required instruments we already had and whcih we had to buy. There we found multiple Strain Relief Cables of Type A, 2 Collimating Tubes, 2 Laser diodes and 2 LD1100 Drivers. I setup the circuit and checked the collimating tubes and the laser diodes. After testing these instruments, I made another list of the instruments that still needed to be bought and sent them to sir. All of these are listed at the end. I realised that the current design of the SPR setup was limiting the range of the internal angle for which I could get reflectivity measurementst. Therefore, I thought up of three redesigns but ultimately decided it was best that I changed the existing setup minimally so I changed its oreientation in such a way that decreased the upper limit of the range of internal angle but increase the lower limit. With the new setup, I coul now get internal values ranging from 20 to 70 degrees which is exactly the range in which the SPR Curve is expected. I performed the experiment twice and got two new datasets but unfortunately, there seemed to be a problem with the laser so that its intensity varied uncontrollably during the experiment which resulted in faulty datsets. I tried changing the batteries but this did not have much effect on the varying intensity so it seemed the problem is with the laser itself. Since I was performing this experminet on Saturday, I could not get a replacement laser from the store and have to perform it on Monday instead. Resources: (1) The design and construction of a cost-efficient confocal laser scanning microscope Peng Xi and Bartlomiej Rajwa (2) http://www.physics.emory.edu/faculty/weeks//confocal/ (3) https://www.microscopyu.com/techniques/confocal/introductory-confocal-concepts (4) Basic Confocal Microscopy by Robert L.Pierce & W.Gray Jerome Shopping List: Laser Diodes: 1)https://www.thorlabs.com/thorproduct.cfm?partnumber=L515A1(515 nm) 2)https://www.thorlabs.com/thorproduct.cfm?partnumber=HL6358MG(639 nm) Collimation Tube: 1)https://www.thorlabs.com/thorproduct.cfm?partnumber=LT230P-B Instruments Available in the Store: 1)https://www.thorlabs.com/thorproduct.cfm?partnumber=SR9A (Strain Relief Cable) 2)https://www.thorlabs.com/thorproduct.cfm?partnumber=LD1100 (Driver) 3)https://www.thorlabs.com/thorproduct.cfm?partnumber=LT230P-B (Collimation Tube) 4)https://www.thorlabs.com/thorproduct.cfm?partnumber=LT110P-B (Collimation Tube) 7 Got a replacement laser from the store but discovered it had a pretty large beam radius compared to the one I was previously using. So, I decided to try and use one of the collimated lasers I had tested last week. The connections had been broken between the laser diode and the driver, so I soldered them on and tried setting up the experiment. The colimated laser, while being very sharp and focused i.e having a relatively small beam radius, was so low-powered that I could not use it in the present experiment. I then tried using another laser which also had a small beam radius but unfortunately, its intensity was also subject to flickering over any prolonged use. Therefore, the only option I had was to use the red laser with the large beam radius I had gooten form the store at the day's start. I got two datasets using this laser but they were not encouraging, pointing some critical flaw in my experiment. I then decide to test whether my laser was being properly p-polarised and discovered that, unlike the previous laser, this one came polarised out of the box. Hence, I adjusted my polariser to ensure p-polarised light reaching the prism. To reduce the time taken during manually measuring data, I used a Physlogger provided by Dr. Sabieh to automate data aquisition from the photodiode. The associated program allowed various frequencies of data aquisition but since I had set the speed of the prism and the photodiode at 2 and 4 respectively, I thought it best to get data at 2Hz. The speed mentioned is in unkown units so I could not accurately relate the angle through which the prism moves and the corresponding time taken at any given point during the experiment. My goal was to plot the values of the photointensity measured using the Phsylogger with the angle through which prism had moved but due to the above-mentioned constraint, I could not do so directly. So, I assumed a linear relationship with time and in the MATLAB I wrote for data analysis, I worked out the angle at any given point by incrementing the angle according to the time that had passed since the start of the experiment. I averaged over the aquired values according to the frequency to generate an averaged data set and then plotted this against the values of the internal angle. Having automated the data aquisition and analysis process, I proceeded to take multiple datasets but the results showed a lot of variation. While for most datasets there is a sharp decrease in the measured photointensity at the expected value, the prcoess of avaerging is apparently distorting the overall values such that there are sharp peaks and troughs in all the plots even though theoretically the data should be smoothly varying. i think this is due to the sensivity of the data aquisition equipment and the variation in intensity of the laser. Will need to further test next week to come to a conclusion regarding this. 8 9 10 11 12 13 14

Furqan Hashmi

Week Activity 1 1. Understood the theory behind cyclic voltammetry and the working priciple of a potentiostat (and a galvanostat). 2. Performed a thorough literature review of the following papers: (a) Building a Microcontroller Based Potentiostat: A Inexpensive and Versatile Platform for Teaching Electrochemistry and Instrumentation. (b) A Practical Beginner’s Guide to Cyclic Voltammetry. 3. Prepared the Ag/Ag Cl electrode and placed it in the lab drawer for future use. 4. Starting working with the potentiostat. For some reason, the readings were not correct as a constat current value was displayed when a resistor was connected as the load. 2 Tried to solve the problem with the circuit, haven't been succesful yet. It seems that the circuit is unable to vary the voltage. That leads to a constant value of voltage input and since there is no variation, the current value is also constant. However, I now have some doubts regarding the circuits ability to read the current value since it always displays a current value of around 600uA no matter what the resitance load. Been trying to reach Shafique sahb regarding this problem. Will try updating the Arduino code in the circuit once I acquire a backup copy of the original code. 3 1) Started using an oscilloscope to troubleshoot the circuit. When the code is run and a voltage profile at the Working electrode is taken with respect to the reference electrode. The voltage value is constant which it shouldn't be. This indicates towards some problem with the summing amplifier because the voltage is not being ramped up. I'm now carefully studying the summing amplifier circuit to solve this problem. 2) Another problem that I have noticed is that the op-amps used in this circuit Spent a major part of the week debugging the cicuit. Problem found (and most probably) resolved. Turns out the the Resistor in the RC integrating circuit didnt have a resistance high enough to perform proper integration. This was causing a very small sepp in the voltage which was of no use. Additional resistors at the CE point were added and proper data sets hav now been obtained. I now plan on calibrating the cicruit and 5 Calibrated the circcuit with a ressitor as a load. Tried performing cyclic voltammetry on Potassium Ferricyanide. Didnt work, will see what the problem is. 6 As per Sir's instructions, checked the circuit for a potential ramp. while there was a potential ramp (-5V to 5V) before at the WE input, there wasnt one 7 8 9 10 11 12 13 14

Mohsin Raza

Week Activity 1 I spent the week 1 of Lab reading Luis Jos´e Salazar Serrano's PhD Thesis titled: Weak Value Amplification: New Insights and Applications. The thesis shows how Weak Value Amplification (WVA) can be used to improve specific experimental technologies. It starts with giving reader a breif over view of the WVA scheme and then goes onto to discuss applications of WVA in different experiments. Luis et al. were able to measure femtosecond temporal delays between pulses much smaller than their pulse width (~10-100 fs). In addition, Luis describes how they developed an innovative experimental scheme that makes use of the interference effect present in a WVA scheme to generate a highly-sensitive tunable beam displacer that can outperform the limitations imposed by the use of movable optical elements. They were also able to increase the sesitivity of Fiber Brag Grating (FBG) temperature sensors using the WVA scheme. The thesis ends with a discussion on the limitations of the idea and talks about what WVA can offer and what it can not. Reference: Salazar Serrano, Luis José. "Weak value amplification: new insights and applications." (2016). I also went through following literature to better understand the concept of WVA: - Duck, I. M., Paul M. Stevenson, and E. C. G. Sudarshan. "The sense in which a" weak measurement" of a spin-½ particle's spin component yields a value 100." Physical Review D 40.6 (1989): 2112. 2 I was assigned by Dr Sabieh to do the experiment do experiment 1.5 from Physlab 100 on Wednesday. The experiment is titled "Optical Activity of Chiral Solutions". I decided to do the experiment on the weekend but was unable to do so due to sudden sickness. I did however go through the manuals of 1.5 and 1.22's manual and did the pre lab questions. 3 Wednesday: I went to Lab on Wednesday and tried to do the experiment but the resistance of LDR is fluctuating. I closed the light but the reading was still fluctuating, this might be because of sunlight coming through the windows. I will try doing the experiment during the night today (wednesday). I tried to perform the experiment at night but the output of red HeNe Laser remained unstable. The key of green laser was not working so I am delaying this till tommorrow. Thursday: The output was found to be much more stable with the green laser. It was however noticed that the resistance of LDR increased steadily as the time progressed, we beleive it mght be beacuse of the temperature depedency of LDR which we are ignoring for the purpose of our experiment. We have therefore replaced the LDR with a photo dectector which is connected to an IV converter. Saturday: Setting up the experiment took 20 minutes (aligning laser, setting up the IV converter, background reading etc.) and the battery of laser ran out as soon as I started the experiment. I charged the battery for around 40 minutes but it lasted only for a few minutes after that. Only 1 battery is functionaning, all other are either drained or not working. I am putting this battery on charge for now. While the battery was charging, I decided to test my light detection scheme (i.e Photodetector+IV converter+Voltmeter). I tested them with the HeNe THOR Labs laser from experiment 3.3 in PHY300 Lab. I recorded a very stable value, confirming that my detection appartus is working as it should. 4 Monday: The old HeNe laser was replaced by a new one. Malu's principle was verified to a very good accuracy. The green laser was converted from battery to permanent power with a plug, malu's principle was verified using the LDR based detector. Data from both experiments are displayed in the Lab notebook. For both experiments, I took the data and loaded it into MATLAB, where I fitted the Malu's principle equation to them. Friday: The optical activity of sucrose solution was measured and was found out to be 1.4 degrees with a standard error of 1.85 degrees. The specific optical activity of sucrose solution was found to be 6.25 as opposed to the expected value of 66.37. I beleive the reason is because the sucrose solution is non uniform, the sucrose crystals are visible at some point and can be seen floating around. Ideally, the solution should be prepared again and the experiment done on it. I will do that once I am done developing the WVA scheme for the experiment. 5 Monday: I consulted several literature articles for my WVA amplification scheme. They are listed below in enumerated form: 1. Li, Dongmei, et al. "Application of quantum weak measurement for glucose concentration detection." Applied optics 55.7 (2016): 1697-1702. 2. Li, Dongmei, et al. "Optical rotation based chirality detection of enantiomers via weak measurement in frequency domain." Applied Physics Letters 112.21 (2018): 213701. 3. de Lima Bernardo, Bertúlio, Sérgio Azevedo, and Alexandre Rosas. "Ultrasmall polarization rotation measurements via weak value amplification." Physics Letters A 378.30-31 (2014): 2029-2033. 4. Pfeifer, Marcel, and Peer Fischer. "Weak value amplified optical activity measurements." Optics express 19.17 (2011): 16508-16517. I used article [2] and article [4] to sketch to possible working scehemes for our experiment. I summarised the gist of articles on my Lab Notebook and presented the work to Dr Sabieh. We decided that we are going to use the scheme proposed in article [4]. Sunday: I tried to gain some expierence with Lock-In Amplifier by going through 2.2: "Introduction to Lock-In Amplifier". 6 I started performing Experiment 2.6 from PHY 300 LAB. The experiment is titled "Phase sensitive Faraday Rotation". The first part of the experiment was to find resonant frequency of the Helmholtz coil, the resonant frequency was found out to be 821.8 Hz. The second part was to find a callibiration curve of the magnetic field of Helmholtz coil with respect to the current passing through the circuit. A linear relationship was found. The next step was to verify Malu's principle, my data agreed to the principle to a decent accuracy. All the relevant data and graphs are presented in Lab notebook with fitting equations and parameters specified where needed. The final part of the experiment was to find the Verdet constant of Terbium Gallium Garnet (TGG) crystal. I was unable to perform this aprt because the Lock-In Amplifier was not locking the signal of from the photodetector. I tried debugging the set up by changing BNC cables, connectors of the electrical components but in vain. It was noticed that the Lock-In Amplifier (LIA) was not locking the signal when the amplitude of function generator was reduced below 2.5V. The Lock-In works perfectly fine for amplitudes above 2.5V. The reference channel is sensitive to signals above 400mV as mentioned in the manual of SR-850 (our Lock-In Amplifier). I was not able to identify the reason for it's decreased sensitivity. This week, I also spent some time going over the reference paper more and writing things down, trying to understand the content in full detail. 7 8 9 10 11 12 13 14

Amna Najam

Week Activity 1 Temperature control with the help of PID controller. Read through Lab manual and literature online. Operated PID and figured out how changing the P, I and D values affect the time temperature takes to reach the desired value and by how much it overshoots. Started with low temperature of 50*C. Managed to minimize the time and overshoot by changing P and I values. With the inclusion of D value the temperature trend overshot by a lot and oscillated around the desired temperature without steadying out. Failed to set a optimum D value. 2 Continued with Temperature control using PID controller. This time desired temperature is set at 100*C. The values of P, I and D are varied. D did not create big overshoot or frequent oscillations this time. Learned that there is a trade off between overshoot and the time it takes to reach a desired temperature. This time around used a stop watch to keep a check on time. Each setting was observed for 30 minutes. 3 Temperature control using PID continued. Setvalue = 150*C. More systematic record of data collected by noting down the temperature at set time stamps manually to be able to plot the data sets for better visualization. The optimal value of P=10 was set. The observations were extended to 1 hour to better observe temperature oscillations. Since the observation time was extended the progress has slowed. The values of I and D remain to be set. Went half way through the article on ferroelectrics (Electrical Measurements of Ferroelectric Properties by Mark Stewart et.al). 4 Synthesis of Barium Titanate pellet using solid state was sucessfully carried out. Barium Oxide was also synthesiszed in lab using solution combustion method as a precursor for Barium Titanate. The temperature control was set at P=40, I=20, and D=40. The temperature overshoot and oscillations were minimum at this setting. The overshoot and oscillations at this setting was observed for different set temperatures. Literature consulted for synthesis processes: Synthesis and Characterization of Barium Titanate by Solid State Reaction by Monica de Amdrade et al. Preparation of Barium Oxide by Henry W. Rahn et al.(United States Patent) 5 The circuit components required to study the hysteresis loop of Barium Titanate are studued and checked. The IV converter, an op-amp based current to voltage converter is checked by connecting it to the current source and measuring voltage across it by using the mulltimeter. The current source was also checked by connecting it in series with the DC power supply and multimeter in ammeter mode. 6 The sawyer-tower circuit with the modification with the IV converter was set up and checked. The circuit is used to observe the hysteresis loop for the Barium Titanate pellet. The input voltage was connected to the X channel of the oscilloscoope and the Y channel was connected to the output voltage across IV converter. A lot of noise was observed in the output signal, in order to minimize the noise maximum gain of 1 mega ohm was set at the IV converter. This lead to the cutoff of the output signal at higher input voltages. The input votage is a 1kHz transforner with voltages ranging from 200 Volts to 1000 Volts. No hysteresis loop was observed. The temperature was varied between room temperature and 200*C 7 The data collected in the previous week was analyzed. The pellet of Potassium Nitrate was used to observe the hysteresis loop. A hysteresis was observed at room temperature but no hysteresis behavior was observed at higher temperatures. Similar noise problem and the cutoff of output voltage was observed in this case. The IV converter gain could not be lowered. 8 9 10 11 12 13 14

Hudaiba Somroo

Week Activity 1 For the first week of Engineering Project Lab, I worked on completing a lab manual for Physlab 1. The experiment was based on maximizing the overhang due to a stack of books - something me and my former lab partner had worked on during Physlab 2. Due to earlier familiarity with this problem, I did not have to research much on the subject matter and most of my time was spent on rectifying existing mistakes as well as making structural changes in the manual. In doing so, I introduced a section on mathematical induction in the manual encouraging students to prove the harmonic sum that is also derived in steps that encourage students to carry out partial sums at each level. I added an introduction hoping to intrigue and interest a student reading it. I worked on giving a step by step guide to the experiment in a manner that would require data collection, programming, but also hands-on manipulations with the provided apparatus. Texts consulted included primarily Paul J. Nahin's "In Praise of Simple Physics" and then I also consulted a paper published by the American Mathematical Association on the Overhang problem. I consulted the latter as I was hoping to incorporate other models for the overhang problem that could be incorporated in the existing manual. However, finding the paper more focused on mathematical proofs, I could not quite reconcile its ideas with the existing manual and so dismissed the idea. Instead, I concluded the manual by requiring students to build their own models of an overhang and see if they could come up with a mathematical way to describe it. 2 Revised the manual by making all changes recommended by Dr. Sabieh and Kaneez Amna who had also carried out the experiment and collected sample results. 3 Carried out the experiment for stacking of blocks again. After doing so, I worked on writing a solution manual for the experiment as well as compiling sample results in a presentable form. Since Ma'am Kaneez had carried out the experiment for a greater number of blocks, I used her data sets to generate graphs of projections and overhangs against n. The experiment was made ready to be installed in the lab with a completed lab manual, a reference solution, and sample results.  Started researching on designs for a cold stage which would be my next task. 4 I started by looking into why cold stage microscopy is used. I came across a 1979 paper that dwelled on cold stage microscopy for fast frozen liquids. It involved both procedures for sample preparation as well as loading the sample on to the microscope's cold stage. I found it useful to the extent that it helped me understand how the original liquid structures are preserved by crystallization by creating sharp temperature gradients that prevent molecules from forming closely packed structures. Rate of cooling thus becomes a necessary concern and I am expecting this to show up at some point later in this task. I moved on to consulting designs for the cold stage. I looked into a rather simple design recommended by Dr. Sabieh that involved using a Peltier cooler to design a cold stage. After discussing the design with Umar Hasan, I was informed that they had used Peltier Coolers to reach temperatures down to -20C. After this, I came across building a stack of Peltier coolers that could be used to create a sharper temperature gradient. Umar Hasan thinks it should work and asked me to come up with a schematic for the cold stage whose dimensions would fit the light microscope in the lab. I was also asked to familiarize myself with the Brownian Motion experiment in the lab and familiarize myself with the microscope. I familiarized myself with the microscope's basic operations and took dimensions of the stage in detail to see how the cold stage could be fitted on it. With the heat sinks that were available in the lab store, I was able to come up with a simple design that would involve a copper board with a stack arrangement of Peltier coolers with a hole drilled through them, and a heat sink attached such that its lateral surface would be perpendicular to the base of the cooper board. Next, I need to understand each of these devices in greater detail and start building the design while monitoring temperature ranges. Talmon, Yeshayahu, et al. “Cold‐Stage Microscopy System for Fast‐Frozen Liquids.” AIP Publishing, American Institute of Physics, 1 June 1979, aip.scitation.org/doi/10.1063/1.1135920.. 5 Went through lecture notes on thermal dissipation in electrical systems provided by Umar Hasan. Could not precisely model how thermal dissipation would take place in my schematic of the cold stage. Realized that we would mostly have to rely on trial and error for the most part. Set up the initial design of the cold stage. This included cutting a copper board of 60mm x 80mm, grinding off the edges, polishing the surface, drilling holes, connecting a heat sink and a peltier cooler. Machining help was provided by lab members. Current apparatus has now expanded to include power supplies(HY5003), crocodile cables, the cold stage in design stage, peltier coolers(TES1-03130), and a thermal camera. Tuesday: Set up the thermal camera, installed FLIR tools. Noted down temperature changes of the Peltier Cooler for 1V while operating the circuit for short time periods of 0-30 seconds. Took images from the thermal camera at various times. Need to explore efficient ways to obtain temperature v/s time graph. Ali Akbar has suggested that I could feed a temperature range with an incremental value that allow me to monitor temperature changes in a continuous manner.  Sunday: The time-lapse mode on thermal camera has a minimum interval of 15 seconds. As such, this method will not work for building a temporal plot for a duration of 30 seconds as temperature increments are noticeable over shorter time intervals. The thermal camera does allow for video recording in thermal mode however there are no options to save the file in the .csq format which is supported and editable by FLIR tools. The camera only saves file in Mpeg format. However, recording a video was helpful as I could easily track the maximum and minimum temperatures and build temperature v/s time plots. The minimum temperature corresponds to the Peltier Cooler while the latter corresponds to the copper board. Had to slow the videos down to 0.4x which helped me obtain abundant data points and I was able to obtain exponentially decaying curves for the two arrangements: with and without glass slide. Without the slide, the curve decays faster and in the same duration, reaches a lower temperature. 6 Video Processing:Could not obtain temperature v/s time plots via FLIR Tools as the T420 does not support .csq and .seq files. Three options were available to obtain the temperature v/s time plots. Option 1 was to do so manually which was both time consuming and could be erroneous if one were interested in minute details. Option 2 was to import the videos in MATLAB, crop out the peltier region and carry out a comparison of its RGB values in stored per frame in an mxnx3 matrix with the calibration scale. This could not be done as the calibration scale was not available. Option 3 was to implement a deep learning algorithm on the videos that would read off the minimum temperature readings. Option 3 was explored and implemented with the help of Harris Noor from the Computer Science department who offered a step-wise solution to the problem detailed in the lab notebook. However, this raised some issues with the tesseract library on my laptop and such some time was spent debugging. Finally, we were able to obtain the temperature v/s time plots with great precision. This method can now be implemented on any set of temperature readings taking from T420 in the lab. Exploring TEC1-12710: The 40x40mm Peltier Coolers could not be adequately cooled by the existing setup due to their greater surface area. This becomes counterproductive as the copper board heats upto temperatures of 70-80C. Need to provide a Copper base with greater surface area and more efficient heat sinks. Made videos to obtain temperature profile of TEC1-12710.  Will use these various temperature profiles to create comparisons as the experimental set up is upgraded.  7 Week 7: Monday: Cold stage design: set-up was upgraded by making use of a PCB, two heat sinks, and two TEC1-12710 Peltier coolers. This did not work as the PCB contains small amounts of Copper and as such, did not provide the required thermal conductivity.  Preparation of glass slide with water drops and observation under microscope: After various trial and error method with available non-polar substances, cooking oil was rubbed on the surface of a glass slide and a syringe was used to place water droplets. This allowed me to view individual water droplets in great detail.  Saturday: Two new designs have been made available. Both have a copper base but have different heat sinks. Temperature profiles for the TEC1-12710 were obtained with both the designs. Of this, the one with a single heat sink proves to be more efficient. The optimal voltage is at 12V, 2.9A allowing for temperature to drop till -10.5C.  A Peltier stack was also explored. Bottom peltier cooler was at 12V while the topmost was at 6V. This dropped temperature to 0.8C. Literature Survey:Read through Cleaning up our water: reducing interferences fromnonhomogeneous freezing of “pure” water in droplet freezing assays of ice-nucleating particles." 8 9 10 11 12 13 14