Microprocess Engineering by Hadiza Auta

Lecture 1.3

2020-11-07 16:57:24 UTC

Please can you go over the key points from Lecture 1.3. It is hard to understand the key concepts without much writing on the slides or without a video.

HAA_Reply to Lecture 1.3

2020-11-07 23:30:01 UTC

Lecture 1.3 is a continuation of Lecture 1.2. It is basically highlighting examples of real life (company) processes that are already seeing the benefits of uprocess Engineering or its application.

HAA_Note to Class

2020-11-07 23:35:20 UTC

I now have a video for the 2 lectures to help with understanding. sorry, I am slow with videos and notes because I only started the job few weeks back. so! still catching up on a lot - bear with me!

Lecture 1.2

2020-11-08 11:22:33 UTC

Please could you go over the derivation in slide 17? Are we just trying to show that in a micro reactor we would need a much higher velocity to achieve the same Reynolds number as the larger scale reactor?

Lecture 1.2

2020-11-08 14:54:10 UTC

Please could you explain in more detail the consequence of scaling laws in terms of the centrifugal force and its relationship with the characteristic length?

Lecture 1.2

2020-11-08 15:36:44 UTC

Please could you explain the equations on slide 16 in more detail. Particularly, how the equation for the time constant of thermalisation was derived.

Sound Quality on Recordings

2020-11-08 16:25:15 UTC

Thank you for the videos! There are times when the audio quality isn't great and difficult to understand. Can this be improved for future recordings?

HAA Response to Slide Re #

2020-11-08 23:36:49 UTC

I will expatiate tomorrow in class. But yes, increasing velocity by a power of 5 (microscale) might not be practical and we might end up with a rocket speed velocity.

HAA Reply to centrifugal force and time constant of thermalisation

2020-11-08 23:44:22 UTC

Ok, I will show a more elaborate explanation in class

HAA_Audio Quality

2020-11-08 23:51:21 UTC

I will check and see what the issue is and resolve for next time.

Symbols Nomenclature

2020-11-09 09:56:53 UTC

Thank you so much for the videos so far! I was wondering whether it would be possible to have a nomenclature either in the slides so that there is less ambiguity on what the symbols means when we look back on them. Thank you!

Symbols for Mac PDF

2020-11-09 13:11:04 UTC

Could you please ensure that the symbols in the PDF uploads work for Macs? I'm not sure why but the greek symbols do translate on the PDF when opened on Macs.

HAA_Symbol Nomenclature

2020-11-09 18:32:11 UTC

I will address this but these formulas are standard formulas you already should know. So! whatever the symbol used, you should refer to paramaters that relate to those equations from principle. Nonetheless, I will take note of this.
Thank you!

HAA_Something to NOTE for Zoom Class 9/11/2020

2020-11-09 18:34:59 UTC

I notice when explaining the Reynolds number, I said viscosity instead of velocity, this is the same as the misleading symbols you guys are noting**
When I upload todays class, I will find a way to address this!

Panopto

2020-11-10 16:17:36 UTC

Please could you upload the LOIL session to Panopto? Thank you :)

Volumetric Heat Flux

2020-11-13 07:55:55 UTC

Please could you explain how
qv=(Q/Qv)?

Session 1.2 Slide 13

2020-11-13 08:21:04 UTC

Please can you explain why when we work out the relationship between Q and a, we assume that pressure drop over length is constant (with changing a)? To calculate Q’s dependence on a, do we not need to use the pressure drop over length relationship of 1/a² and therefore Q is only proportional to a²? As we do a similar thing when we work out the relationship between pressure drop over length and a, we convert Q into a constant variable first.

Lecture Recordings

2020-11-13 11:31:59 UTC

Please could recorded lectures be uploaded before friday morning so that we don't have to watch lectures over the weekend?

Slide 20

2020-11-13 22:02:36 UTC

Hello, in the LOIL you explain that F is equivalent to mass*acceleration and that we substitute in rho*l^3 for mass and omega*l is velocity. Please could you explain this further as I thought that we would need to have acceleration for the units to work? Thank you :)

Lecture Recordings

2020-11-14 11:36:39 UTC

Please could you let us know where the lecture recordings are? You emailed that they would be uploaded by the end of the day on Friday but I can't seem to find them online? Thank you!

Youtube Videos

2020-11-15 09:20:49 UTC

Can we be examined on information that is in the YouTube videos but not on your slides?

HAA_Lecture Recordings

haa69 — 2020-11-15 13:17:47 UTC

It is now on Moodle. It might take me time but I will eventually put it by the next day or 2 OK!

HAA_Youtube Video

haa69 — 2020-11-15 13:19:04 UTC

No, YouTube videos are not examinable! It is just to help you with applying the knowledge or if it is a video animation, to explain to you better than an abstract or theoretical explanation-Nothing more!

HAA_Slide 20

haa69 — 2020-11-15 14:14:01 UTC

I might have had a slip of tongue (Sorry!)

Force for centrifuges is

F= Mass x (Angular velocity)²x Radius.

That is Mass = density (rho) x volume (l³) Angular velocity = Omega Radius = length (l)

if we substitute in the formula for Centrifugal force above:
F = density x l³ x Omega x l

So! please no acceleration!

HAA_Lecture Recordings

haa69 — 2020-11-15 14:39:06 UTC

I wish I can record all your lectures today and you can have them. I also feel your pain, but know that I just started this position and I have to put material before coming to explain to you in the videos and then prepare for classes.
Note! I don't only teach this course but I have other courses I am teaching. So! I am working tirelessly round the clock to sort everything out.
For now, I am sorry I will have to work at a pace to give you the best! SORRY!

L2 slide 19

2020-11-15 23:50:27 UTC

Could you please elaborate on the point about how when you know the crystal angle of silicon, you can calculate the width? is this W0?

Laser pointer

2020-11-16 09:37:05 UTC

Hi, sorry I think the laser pointer comment was referring to your recorded lectures. We can't see your cursor sometimes when you're referring to something you're pointing to.

Laser Pointer

2020-11-16 09:38:24 UTC

As sometimes the cursor disappears, or the cursor colour is similar to the background/text, making it hard to see.

2020-11-16 09:41:37 UTC

The symbols on your lectures notes for Mac don't translate when downloading from Moodle

Kahoot

2020-11-16 09:57:52 UTC

please could you give explanations of all the kahoot answers so we can know why we were wrong

Practice questions

2020-11-16 10:05:04 UTC

Hello, will you be providing us with example answers to the practice questions?

could you please provide us with the answers to the practice questions

2020-11-16 10:08:47 UTC

HAA_Recordings

2020-11-16 10:29:51 UTC

OK, let me ask Semali where she got hers and try that, in the mean time, I will try and make sure the mouse is visible when I try to drift it around.

HAA_Kahoot

2020-11-16 10:35:09 UTC

We will either discuss them in the next class or during revision week if thats ok.
I want to use the class to explain what is in the lecture notes or address your questions

Plasma

2020-11-16 10:37:19 UTC

Please can you explain what plasma is and how it works. i have never come across this before but you assumed we already know. I dont understand the slides what you skipped, for example what glow region or sheath field etc etc mean.

HAA_Symbols on Lecture Slides

2020-11-16 10:43:56 UTC

I can see all the symbols believe is on the slide here, so! what exactly don't you see? because this slide is complete

Topic 1.2 Slide 13

2020-11-16 10:55:17 UTC

Sorry please can you clarify your response from LOIL 2, are you saying that to relate Q to a, we have to assume pressure drop over length will not change with changing a?

HAA_Practice Questions

2020-11-16 11:32:12 UTC

Refer to the lecture recording and ask about anything you are not confident about during the lecture or during revision class :)

HAA_1.2 Slide 13

2020-11-16 13:52:57 UTC

Yes, you will assume all other variables are constant and relate Q to the scaling factor (a) in this case

Scaling Down and Reynolds Number

2020-11-16 18:31:53 UTC

In your slide, you have written down ℓ = 10mm which is 10^-2but you have said 10nm which is 10^-8and you get λ=10⁵ should ℓ not be 10μm

Also in terms of scaling laws, does ∼ mean 'similar to' or 'proportional to'

Does the characteristic dimension only refer to length (m)

2020-11-16 22:09:03 UTC

This is showing L instead of lamda

Lecture videos

2020-11-16 22:14:12 UTC

Thank you for the lecture videos. I understand that you are new but please could you upload the videos earlier as I don't think it's fair for you to expect us to watch them on such short notice as we also have other lectures and other commitments outside of university.

Symbols Issue for Mcs

2020-11-17 10:01:07 UTC

The symbols on your lectures notes for Mac don't translate when downloading from Moodle e.g. Delta shows a "D" instead of the usual triangle symbol. Could you please upload alternate versions going forward as well as for the previous lectures? Would appreciate if you could address this soon as it is difficult to go over the slides at the moment

Exam Question Examples

2020-11-17 10:36:54 UTC

Please may you go through the solutions in the LOIL or provide the answers on Moodle? It's useful for us to know the answers so we know if we have gone wrong or if we have misunderstood the content.

Slip or Non-Slip

2020-11-17 10:37:13 UTC

Could you please clarify whether slip or non-slip conditions are most common for microfluidic systems, as both were mentioned to be so in the video. Thank you!!

HAA_Lecture videos

haa69 — 2020-11-17 11:01:19 UTC

I will try and upload them in good time for the future. I explained the reason why this week is messed up. Sorry about that!

HAA_Symbol Issues

haa69 — 2020-11-17 11:04:14 UTC

I will check this symbol issue, I have a Mac too and so I am confused to why this is happening.

HAA_Slip/Non slip

haa69 — 2020-11-17 11:05:11 UTC

If I mentioned both in the video, please quote me the timings so I check.
For clarity, in microfluidic systems we mostly experience the slip condition

HAA_Scaling Law and Re #

haa69 — 2020-11-17 11:28:36 UTC

~ means similar to
Can you tell me what slide number this calculation is on please?

HAA_Reynolds no.

2020-11-17 14:47:15 UTC

Yes it is 10 um, the formatting gets mixed up when I run the classes on my Mac. Thank you for noting this!

2020-11-17 15:39:00 UTC

differences circled in red.
Maybe it would be okay if you uploaded the powerpoint version as mac users would then be able to edit the symbols?

HAA_Symbol Issue will be addressed

2020-11-17 15:44:24 UTC

I will sort this out after today, in the mean time, i will upload the PP slides and not Pdf as I assume this helped Sam when I emailed him the slides.

Reply to HAA_Slip/Non Slip

2020-11-17 16:23:15 UTC

Around minute 21:15
You said at the beginning of the slip slide that this was most common so I was pretty sure but then just before changing it you said the other so I just wanted to clarify. But got it now so thank you for the help!!!

Kahoot

2020-11-17 16:34:04 UTC

Can you please let us pick our nicknames for Kahoot? I don't like AdorableSquid

ppt files

2020-11-18 07:04:25 UTC

Could you please upload the ppt files of the lectures?

Lecture notes

2020-11-18 12:16:24 UTC

Hi, I was wondering whether you could start using numbered headings/sub-headings (e.g. 3.1, 3.2) in your notes, as I am not sure which slides are related to each topic

Lecture 1.3

2020-11-19 19:21:09 UTC

Are we expected to know examples of different companies already using microreactors that are outlined in this lecture for the exam?

Can you please provide solutions for Question 1 of the example questions you did not go through it in the LOIL?

2020-11-20 15:12:15 UTC

Symbol Issues

2020-11-21 12:11:44 UTC

Please could you fix symbols or upload powerpoint slides as the pdf downloads keep showing incorrect symbols or showing boxes (I use a Windows PC) . Example from 3.2:

Re vs mixing quality - Slide 14

2020-11-21 14:01:40 UTC

Please you go over again why the mixing quality decreases when we initially increase Re?

Slide 17

2020-11-21 14:10:28 UTC

Please can you clarify what in plane and outer plane turns are?

Slide 6

2020-11-21 14:23:40 UTC

For a rectangular channel is the diffusion time the ratio of the width of the channel squared to the diffusion coefficient? As you don’t say squared in the lecture but the formula has b squared?

Video lecture 4

2020-11-22 15:27:44 UTC

Thanks for listening to our feedback. This video lecture was much easier to follow :)

HAA_Lecture 1.3

haa69 — 2020-11-22 20:43:47 UTC

Not at all...It will be good to know but you wont be asked in exam

HAA_Solutions to Some problems

haa69 — 2020-11-22 20:45:22 UTC

You should at least attempt it, we will do similar questions in the IPT and in revision LOIL

HAA_Ppt Files

haa69 — 2020-11-22 20:46:52 UTC

I have uploaded the files

HAA_Re Vs Mixing quality

haa69 — 2020-11-22 20:48:27 UTC

I will go over it in the LOIL tomorrow

HAA_Plane and out of plane

haa69 — 2020-11-22 20:49:27 UTC

It is just the angle you can see (in plane) and what you cant see (out of plane) from the capture view

HAA_Slide 6

haa69 — 2020-11-22 21:22:41 UTC

Yes it is squared, I might have just missed it...

HAA_Video Lecture 4

haa69 — 2020-11-22 21:23:41 UTC

This is encouraging, I am learning every day. Thank you to those of you that advised about the laser pointer and those that gave their feedback on other ways to improve the learning.
I appreciate!

Slide 9

2020-11-23 08:06:33 UTC

You mention that we can only achieve maximum 50% separation in an H-filter. Please could show what formula we would actually use to calculate this separation percentage?

Problem 1 - blood separation

2020-11-23 10:00:27 UTC

Hi Hadiza, please can you post a table that you are making in the lecture, of number of H filters with respect to amount recovered, but can you do it in terms of mass fraction or molar weight. I am a bit confused about this.

H filter question

2020-11-23 10:35:09 UTC

Hi Hadiza, in the H filter question, what did the column called "Recovered" signify?

HAA_H filter

2020-11-23 11:11:11 UTC

It is how much of the initial we are able to separate

CFD simulation

2020-11-23 21:34:12 UTC

On the graph, do the peaks of Nu at about 100um and 1200um correspond to first 90 degree bend and second bend ?

Dimensional analysis

2020-11-24 09:19:41 UTC

Could you please go over slide 8. Not sure how you got to (n x Dh^2) = const.

Heat flux versus amount of heat

2020-11-24 10:33:20 UTC

In Slide 6 and 7, you swap between the term the amount of heat and heat flux, but use the same symbol qh - please could you use different symbols for heat flux and amount of heat to make it easier to follow.

HAA_CFD Simulation

2020-11-24 13:18:47 UTC

Yes, but I recommend you access the reference for more information (it is in the bottom of the slide).

HAA_Dimensional Analysis

2020-11-24 13:24:46 UTC

If you listened to the video carefully, I said I will go through it in class.

Heat Flux Versus Amount of Heat

2020-11-24 13:25:54 UTC

There is no mistake in the use of qh from what I am seeing....both heat conduction and heat convection fit.

Can you upload the ppt Lec1-3?

2020-11-24 13:49:16 UTC

Slide 8

2020-11-24 14:01:42 UTC

Could you explain how you got the reduction to 1/4 of original length?

micro HX

2020-11-24 15:01:22 UTC

On the first slide can you please clarify whether micro HX are that of size < 1 mm or < 1 um

Problem 2 in LOIL

2020-11-24 17:41:55 UTC

In your 2nd problem in the LOIL, it says to calculate t2, the temperature of the hot fluid at the outlet. Surely, this will be lower than t1 (the hot fluid at the inlet), as it has transferred heat to the cold stream.
So surely:
66.3=t1-t2,
therefore t2=-46.3 degrees?

HAA_Problem 2, LOIL 5

2020-11-26 15:20:58 UTC

1) If you notice t1=20C from the question. Surely, this is wrong (if it said it is a high temperature feed, it will definitely not be 20C)...I should have changed this to t2 (my apologies).
The question should be to calculate t1.

2) I have corrected the Question now because it was mis-worded and have uploaded the correct answers too.

3) Check your dimensional analysis, 66.3 is in Kelvin.

Thank you for noticing this!

Slide 5 and 6

2020-11-28 13:01:52 UTC

Please can you clarify the range of Kn we get slip flow in? From slide 5 it looks like we have slip flow when 0.011 and transitional flow starts at Kn>1. Whereas in the graph on slide 6 it looks like slip flow is only when 0.010.1 and when Kn>0.1 we have transitional flow.

Slide 10

2020-11-28 16:00:56 UTC

Please can you explain what r and R are on this slide? As r seems initially to be the diameter of the droplets but then it is used again to define when surface energy is lower for drops in the equation r>3R/2 but this r seems to be the length of the jet. Therefore, are these 'r's different? Or please can you explain how they are the same.

Question 1

2020-11-28 21:56:42 UTC

How do we get the velocity to calculate the Reynolds number?

H filter separation

2020-11-29 10:32:42 UTC

Please can you provide an example using concentrations to model this separation? Is the 50% separation effectively saying the below for the first 2 stages? Where A is the large molecule (which we are trying to reduce its concentration down to zero?)

Slide 6

2020-11-29 11:05:40 UTC

Please can you explain how the simplified Navier stokes becomes d^2v/d^2z=-PnL?

Where does the L come frome. Also what is e_x in v=v_x(z)e_x

Can you upload the ppt Lec1-3?

2020-11-29 12:33:03 UTC

Symbols

2020-11-29 13:32:39 UTC

Please can you make sure you define what you mean by each symbol, lecturers often use different symbols to each other so it can be confusing.

N.S Solution

2020-11-29 14:29:17 UTC

Please can you show us how to get to the equations in slides 6-7 and define some of your notation as each lecturer uses different ones (and we covered TP2 3 years ago) :)

LOIL 5 recording

2020-11-29 17:36:34 UTC

can you please upload the recording for LOIL 5.

Two Phase Poiseuille Flow

2020-11-30 08:32:10 UTC

Can you explain the last boundary condition for2 phase posieulle flow? What is sigma in this last condition?

Navier Stokes

2020-11-30 08:38:13 UTC

Please can we have some practice problems so that we can lear to apply the NS equation?

Force balance

2020-11-30 09:20:40 UTC

How can we equate the forces in the droplet when they are perpendicular and not in the same direction?

Youtube Videos

2020-11-30 16:59:15 UTC

Please can you clarify whether the Youtube Videos you have linked are examinable - in the lecture video you state we must watch some of them, however you have linked 8 different videos in just lecture 7.1. Are they examinable or are some for further interest/understanding?

Slide 12 - Electrowetting valve

2020-11-30 17:13:53 UTC

On slide 12 why does closing the circuit change the shape of the liquid front - the change from picture a where it is ')' to picture b where it is '(' ?

Practice Problem 3 Lec 6

2020-11-30 17:16:26 UTC

In this problem for part (a), Capillary number is given (we don't have to use it) as 3 mm. I thought this number was dimensionless? Could you please clarify as we haven't done any example with it? Thank you!

Slide 14 graph

2020-11-30 19:09:20 UTC

Hi Haddy, could you please explain what channel gap (d) and electrode side length are? And how do they relate in the graph on slide 14?

EOF and EPF

2020-12-01 14:01:36 UTC

Please can you summarise the difference between EOF and EPF?

Examples

2020-12-01 16:06:59 UTC

Can you show an example of how we might use the equations in the final slides in the exam?

EOF in cylindrical channel

2020-12-01 16:15:33 UTC

Why when ions flow from cathode to anode but velocity profile is not in the same direction.

Velocity Profiles

2020-12-01 17:18:50 UTC

7.2, slide 13: you mentioned the electric field goes from +ve to -ve (right to left in the diagram). How come the velocity profile is in the opposite direction (left to right in the diagram)? Similarly with slide 15. Can you also provide further explanation of the velocity profile in the valve solution?

HAA_PPT Lec 1-3

2020-12-01 23:42:52 UTC

OK, it is done.

HAA_Symbols and Nomeclature

2020-12-01 23:44:47 UTC

I believe that for any equation that is very applicable to this course, I have elaborated what each symbol represents. Especially in the video recordings.
NOTE guys, If it is a standard equation e.g. Re #, Hagen Poiseuille etc, I expect you to know what would be the ratio to the other. Example, Reynolds number is the ratio of inertia to viscous forces; therefore whatever symbol I use, I expect you to know whats in the denominator and what the numerator is :)

LOIL 7

2020-12-02 17:01:07 UTC

can you please upload LOIL 7 recording
thanks

HAA_Response

2020-12-02 23:31:48 UTC

I have read all the questions and will respond by the weekend pls

HAA_Response

2020-12-02 23:32:42 UTC

I will respond to all questions by weekend pls

2020-12-03 16:24:06 UTC

In your problems for part 7 can you please explain how you got your mathematical answers in Q2? Also in your Q3 can you explain which way both the pressure flow and elecroosmotic flows are going? (in your lectures you interchange between channels having -ve walls and +ve walls which may be causing me confusion). In my understanding it is the Pressure flow going towards the right and the EOF going to the left?

Two-Phase Poiseuille Flow

2020-12-04 06:53:56 UTC

How does the density of the fluids affect the flow? Does the fluid with the higher density move more slowly?

Slide 12 - Electrowetting valve

2020-12-04 08:45:16 UTC

Please can you explain why the liquid stops when it reaches the plain Teflon - as you mention earlier in the video that we have non-wetting between plain teflon and water which gives slip behaviour so wouldn't the liquid then slip along the surface in slide 13 example? Also in lecture 3 you say that we have the slip condition between water and PTFE due to the hydrophobic interaction. So why is the water not slipping now?

Problems Lecture 7.2 Q2

2020-12-04 14:06:22 UTC

Please can you explain again the shape of this velocity profile and how it changes when the valve is open/closed?

IPT

2020-12-04 15:29:31 UTC

Following on from the screenshot that was shared in the IPT regarding the EOF. In your 7.2 lecture video you state that there will be zero net flow in the monolayer - if this is the case how can we have a parabolic flow profile that leads at the walls in the direction of the EOF? please could you explain this further of why there is maximum flow at the wall?

Practice Question 2

2020-12-05 19:11:31 UTC

2i) I get different values for the maximum pumping capacity per voltage (2.12x10^-12 m^3/sV) and for the max operating pressure (56 Pa/V). Is zeta times epsilon =7x10^-10? (it is hard to tell from the slides)

velocity profile

2020-12-05 20:24:52 UTC

why is the velocity profile in slide13 of topic 7.2 towards the left? is it because in this case you are considering a positively charged surface and hence, the EOF is based on the flow of negative ions i.e towards the anode? Also the adjacent profile is just the profile of the charge density? could you please explain more about it.

velocity profile in Q2

2020-12-05 20:43:19 UTC

why do we have a parabolic velocity profile when we overcome the pressure flow? is it because the bulk fluid in this case is moving unlike under normal conditions where it is stationary (neutral, resulting in a flat velocity profile)? why do we have a maximum velocity in the bulk?

IPT

2020-12-06 00:00:08 UTC

for Q2 c)
you forgot to convert the 40 C to Kelvin.

IPT

2020-12-06 01:13:06 UTC

For Q2c what is the relationship of the Qout with the characteristic length is it Qout~l? What exactly makes the heat exchange more efficient?

IPT

2020-12-06 01:20:15 UTC

In Q4, why did you first write deltaP/L ~ l^-4 and then fore the second part you wrote its as deltaP/L ~ l^-2?

IPT Solution

2020-12-06 08:32:44 UTC

Please can you upload the solutions to the IPT questions

7.2 Slide 13

2020-12-07 12:48:13 UTC

Does the direction of the velocity profile depend upon the direction of the electrical field or is it just dependant on the charge

2020-12-07 17:01:10 UTC

Please can you show us how to get to the equations in slides 6-7 and define some of your notation as each lecturer uses different ones (and we covered TP2 3 years ago) :)

2020-12-07 17:51:54 UTC

HAA_Problem 2, LOIL 5

1) If you notice t1=20C from the question. Surely, this is wrong (if it said it is a high temperature feed, it will definitely not be 20C)...I should have changed this

HAA_Slide 5 and 6

haa69 — 2020-12-07 23:15:40 UTC

You cant use slide 5 as a range, because the box drawn is not to scale. It is just to indicate the region.
Look at my response to Slide 6 slip regime below.

HAA_Question 1

haa69 — 2020-12-07 23:19:12 UTC

What is the formula for volumetric flowrate?
That is how you get your velocity.

HAA_Problem 1 Blood separation

haa69 — 2020-12-07 23:22:10 UTC

These devices have their mechanism of operation. So! trying to apply a different model to them will not work.
I will try and find more information about their mode of action and share.

HAA_H Filter separation

haa69 — 2020-12-07 23:25:07 UTC

From the theories of H filter, I have not seen any formulas used except for the empirical ones and the approach as I have shown you in class.
I will do further research and see if this formula fits the actual model behind this device.

HAA_Slide 8

haa69 — 2020-12-07 23:41:13 UTC

Addressed in class

HAA_PPt slides 1-3

haa69 — 2020-12-07 23:42:07 UTC

I will upload them after the LOIL Revision.
Moodle will be updated with all Quiz and solutions after LOIL 8

HAA_Slide 6

haa69 — 2020-12-07 23:47:50 UTC

Proof of equations out of the scope of this lecture. It is just for your reference and nothing more.

HAA_Slide 10

haa69 — 2020-12-07 23:50:06 UTC

The r's are different.
When used for surface energy, it is the diameter of the droplet (R) in this equation.

HAA_2-phase Poiseulle Flow

haa69 — 2020-12-08 12:48:15 UTC

The density does not affect movement but the position of the fluids.

EOF Valve

2020-12-08 17:31:01 UTC

How does it work as a valve if EOF still allows flow in the double layer to the cathode (to the right)? Is the 'valve' never actually fully closed?

Contact Angle & Slip

2020-12-10 13:41:03 UTC

Hi Haddy,
Could you please clarify the relation between the slip/non-slip behaviour and how this is predicted by the contact angle? In slide 5 of 7.1 you mention that water and Teflon will exhibit slip conditions. Is this because the contact angle is greater than or less than 90°? Also, in Lecture 3 you mentioned that we experience slip conditions in microfluidic systems, does this mean the contact angle is always above or below 90°?
Thank you!

IPT2 and IPT3

2020-12-11 08:54:40 UTC

Please can you upload the recordings to these IPTs as those of us in IPT1 haven't see the complete solution to Q2?

Slide 6 Slip Regime

2020-12-13 18:36:34 UTC

In slide 6 the slip flow region ends when Kn=0.1 and transitional flow begins at Kn larger than 0.1. So in the problems Q2, why is Kn=0.265 identified as the slip flow regime, not the transitional flow? Also, is the below question in the Kahoot quiz of this lecture wrong? We cannot use continuum equations if Kn is > or = to 0.1? Additionally, please can you clarify the range of the slip flow region as there are also conflicting values on slide 6, the graph shows 0.01 to 0.1 but the table below the graph shows 0.001 to 0.1.

Upload ppts to lector's 1-3 please

2020-12-14 14:58:30 UTC

Practice Questions

2020-12-15 12:27:24 UTC

What are some advantages and disadvantages of LIGA and photolithography?
Q12/13: What aspects of material selection (other than surface properties) becomes more significant in the microscale vs macro?

Disadvantages of dry etching

2020-12-15 12:32:59 UTC

What is the loading effect?

LOIL 3 exam question

2020-12-15 17:55:31 UTC

In LOIL 3 you gave us a question with a glass microchannel. However for the fabrication technique, you suggested we use NIL or 3D printing. If it's glass, shouldn't we be using photolithography with dry/wet etching instead?

L7. Slide 13.

2020-12-17 15:16:17 UTC

In the diagram on slide 13, it looks like the walls of the capillary have a +ve charge. Does this mean that we have a net negative charge of ions in the diffuse layer, hence why the velocity profile, and net movement of ions is towards the anode? In slide 9, the net flow is towards the cathode. I was getting confused as to why the velocity profile was the same on slide 13, as it is on slide 9, if the cathode and anode switched sides, but is this the reason? Thanks!

Slip Regime

2020-12-17 17:17:33 UTC

Can you use the continuum model in the slip regime?

EOF in Cylindrical Channel Navier Stokes

2020-12-18 00:16:42 UTC

Hi Haddy,
On slide 13, when you mention the assumptions and talk about how lambda d has to be much smaller than the radius, you mention that if this were not to be the case then the whole channel would be like the bulk. However, as lambda d represents everything but the bulk, wouldn't having a lambda d larger than the channel mean that there is a charge imbalance throughout it all? Or would lambda be so big that the charge imbalance due to one surface cancels out that of the other, thereby creating a neutral condition like in the bulk?
Thanks!

Heat Transfer: Slide 7 and 8

2020-12-18 11:42:12 UTC

In slide 7 when we derive the below equation, to make (L/nDh⁴) constant, are we assuming the Qv is constant (and therefore qv is not constant)? And therefore in slide 8 is it meant to say Qv is constant not qv? As we can't use the below expression when assuming dP and qv is constant because for a change in n, Qv will change (Qv=qv*n)?

Heat Flux Versus Amount of Heat

2020-12-18 11:49:21 UTC

heat flux, qh is per area (in slide 6) whereas amount of heat, Qh is just in Watts Qh=qh*A (which is in slide 7 which you have also denoted as qh)

Exam Numerical Answers

2020-12-29 09:39:04 UTC

Please can you upload numerical answers to the previous exam papers?

Q2

2020-12-29 21:28:45 UTC

for your value of Kn=0.0265 you wrote that the continuum model applies. However, in the graph on slide 6 this value lies in the slip flow regime (0.01-1). why did you select continuum flow?

q1

2020-12-29 22:20:08 UTC

is the answer for Le 4mm?

HAA_~Questions under 6

haa69 — 2020-12-31 23:29:08 UTC

I have addressed all the questions here during lectures (LOIL)

EOF Pump and Scale Up

2021-01-01 13:14:16 UTC

In the past paper exams 2017-18 and 2018-19, when it asks for the scale up effects on h, L, V in an EOF pump, can we use the relationships found in slide 8 of lecture 5? Even though in the lecture this was assuming just (Haagen-Poiseuille) pressure flow and in the exam questions we also have to consider EO flow?

IPT recordings

2021-01-01 18:32:46 UTC

You mentioned in one of your LOILs that you would be uploading some IPT session recordings, I was just wondering when they could be expected? Thank you!

Scale Up for EOF with flux

2021-01-02 16:06:35 UTC

In the 2020 Past Paper (Q1ciii) there is a question related to how you would increase the flux to 500x the original and how the voltage scales with flux in the EOF equation. Please could you explain how this would be carried out? Would you consider an increase in area and hence an increase in radius? Or would you consider an increase in area by numbering up? If the first case is correct how would the voltage scale with flux?

Thanks

2017/18 Scaling

2021-01-02 22:48:30 UTC

For the 2017/18 scaling is this working correct? My thoughts were volumetric flux = velocity, and the obvious way to increase velocity at constant flowrate is reduce the diameter. Could we have a similar example?

2017/16

2021-01-02 22:51:45 UTC

For the scaling question, is the below correct, applying similar logic to lecture 5 slide 8, or should we approach it more simply? - I don't think you can apply numbering up to this question.

2019/20 nanoparticle

2021-01-02 22:55:34 UTC

In question 1 d i and ii is the equation for particle production in our course? If so where and what is e in the equaiton -k*tp=ln(1/e)

Past Paper Questions

2021-01-02 22:58:25 UTC

Please can you explain how we should approach past paper questions that ask how we can increase the flux of an EOS with scaling laws. Could we have a similar example?

Extra Problem Sheets

2021-01-02 23:00:17 UTC

I think in the revision session you mentioned extra problem sheets, please could you upload these? Scaling law questions would be especially useful.

2017-2018 Q1b(i)

2021-01-03 18:02:05 UTC

Not sure whether to take the conductive heat flux into account? How is this relevant?

Fabrication methods

2021-01-03 23:33:36 UTC

Hi Hadi, am I right to think that wet/dry etching are not exactly fabrication methods when considered alone, as these are the methods involved in lithography/photolithography to etch away silicon/glass under the photoresist masking layer?

So a possible fabrication method would be e.g., photoresist + wet etching, instead of just wet etching?

EOF Pump

2021-01-04 08:01:14 UTC

Please could you explain how this actually works as a pump? And how the max back pressure = the max pumping capability of the pump?

HE Practice Question 2 L5

2021-01-04 08:21:40 UTC

In this example, please can you can explain why we can just equate the heat generated to the convective heat flux? As we also have the conductive heat flux into the hot channel from the cooling fluid so don't we have to use the overall heat exchanger flux?

Y Junction Microreactor - Past Paper Questions

2021-01-04 09:55:55 UTC

Please can you explain what the question means when it asks to calculate the minimum channel size which there are no transport resistances at the interface?

Past Paper Questions Hydraulic Diameter

2021-01-04 16:20:17 UTC

In past paers, it often gives the width, depth and length of the channel for rectangular channels. Do we need to calculate an equivalent diameter? In the 2015-2016 paper, it asks us to find the height of the channel. To do this, do we need to equate tau_P=1000*tau_D and find the equivalent diameter, then say D=4A/P=2*w*h/(w+h) <-- the equation for hydraulic diameter?

2015-2016 wetting behaviour question

2021-01-04 16:35:12 UTC

If you have an aqueous phase & toluene through a PTFE channel, and the aqueous phase has a contact angle of greater than 90 degrees, what happens to the two phases? Could there be reaction at the interface?

2019-2020 paper

2021-01-06 00:31:06 UTC

Is the whole of part d part of our course?

2019-2020 paper

2021-01-06 00:31:51 UTC

Is the answer to part Ci) 1.6 s?

Model answer please

2021-01-06 00:45:37 UTC

please could you provide us with a model answer to the questions regarding electroosmotic pump in one of the papers? They are much harder compared to the ones we covered in the LOILs and in the IPT
thank you

2017/18 Energy Balance

2021-01-06 11:22:36 UTC

In 2017/18 1 b i) should we balance q1 + q2 + q3 or ignore convective effects as we have in other examples? How do we know when to use conduction or convection? In the same paper, when it says scale up the flux does it mean volumetric flux (velocity) or volumetric flowrate. Thanks.

HAA_Weekend Response

2021-01-07 01:31:14 UTC

All questions were addressed during revision class.

HAA_Problem Part 7

haa69 — 2021-01-07 03:32:54 UTC

Part 7 has 7.1 and 7.2, Lets try and be specific to make response faster for the future.
7.2 (Q2) has i,ii and iii. Which one do you want me to explain?

Pressure Flow profile:
Refer to slide 16 of Lecture 7.2, Q=0 means maximum pressure which means the pressure side will have the parabolic shape. The EOF movement is dependent on the net charges of the channel.

The charge on the channel dictates the direction we will get EOF. So if the channel is -ve charge, then the net flow will be due to accumulation of +ve charges towards the cathode.

If the channel is +ve charge then the net flow will be due to accumulation of -ve charges towards the anode. So just by changing the electrode charge with same channel, you can control the direction of flow.

I hope this is clear. Let me know :)

HAA_IPT

haa69 — 2021-01-07 03:33:33 UTC

The monolayer is a very small percentage of the entire channel and the channel itself is quite small (microsystems are in micron to nanometers). So, it will be overcome by the drag.
You can find more explanation in the email I will send out tomorrow.

HAA_Practice Q2

haa69 — 2021-01-07 03:33:55 UTC

1) Yes, you are right about Zeta x Epsilon value.

2) Qmax is right too but we are using different units-ok!

3) Your Pmax is more correct than mine. So! stick to yours.
Thank you for pointing this out.

HAA_Velocity Profile

haa69 — 2021-01-07 03:34:14 UTC

1) Your reason to why the velocity profile is to the anode is correct. It is because the wall channel is positively charged and hence the dominating/net charges within the channel will change and so will the direction of flow to the right terminal.
2) I am not sure I understand what you mean by the adjacent profile. Is it the pressure side? This notes will be adjusted properly for future because I can see assuming some things are straight forward actually isn't.
So! to answer your question, that will be the pressure profile if at all there is one applied in the opposite direction; but in this case, none is applied and hence no change to the flow side, while on slide 15, where pressure is applied, you can see a change on the flow side.
3) Let me know what slide you are talking about so I can respond properly.
But, if we are talking about velocity profile of the pressure side, I am sure you remember hagen poiseuille from your TP, for the flow side, when the flow is fully developed (see slide 9), then the bulk will be dragged by the diffuse layer, hence why there is movement there.

HAA_7.2 Slide 13

haa69 — 2021-01-07 03:34:27 UTC

The charge on the wall surface will influence the distribution of charge within the channel and hence directing the flow profile to the right terminal.

See my response to a question titled "Problem Part 7" in this column. It should help explain how these work with wall charges further.

HAA_Problem lecture 7.2 Q2

haa69 — 2021-01-07 03:36:15 UTC

Refer to Revision class (recording) and where I responded to answers to padlet questions.
If you want me to explain after listening to that, drop me a message here again and refer it as "7.2 Q2 again"

1.2 scaling laws slide 14

2021-01-08 12:41:41 UTC

Hi. I am still a bit confused about the relation Qv~l^3. from the equation we have that Q~l. why is Qv related to l to the power of 3 and not just to l? Thank you.

HAA_Exam Numerical Answers

haa69 — 2021-01-08 13:21:57 UTC

I only have answers to my exam questions.
Sorry!

HAA_IPT

haa69 — 2021-01-08 13:22:57 UTC

Because the first one is relating deltaP/L to Q while the second part is relating it to the radius.

HAA_IPT

haa69 — 2021-01-08 13:24:08 UTC

1) Q2c, Ok thank you. You can convert and adjust the answer appropriately. I will note it too.

2) Yes - Qout~l
what makes it efficient for the wall thickness of 10um is the thinness of the column wall making it able to transfer more than the generated.

HAA_IPT Solutions

haa69 — 2021-01-08 13:24:18 UTC

Done already!

HAA_ppt slides

haa69 — 2021-01-08 13:24:29 UTC

Done!

HAA_

haa69 — 2021-01-08 13:24:40 UTC

I don't know how many times I will say this, I will only cover what is in the scope of this lecture and not other courses.
Please contact the lecturer responsible for TP2 to explain things to you if you need assistance with it :)
- Btw, which lecture is this? 7.1 or 7.2?
- Just to reiterate, there are no derivations in the exam!

HAA_EOF Valve

haa69 — 2021-01-08 13:24:52 UTC

So! there is no actual valve. It is just being manipulated in the way that it does the function of a valve (control flow).

Example, if you match up the flow side (voltage) and the back pressure, there will be a stand still. You can now lower either side to allow flow in your desired direction.

So!, it is within your control how you want to use EOF and pressure-flow depending on what the application requires. Just a pump or a valve or for mixing etc.

HAA_L7 Slide 13

haa69 — 2021-01-08 13:24:58 UTC

Everything you mentioned is absolutely correct!
Let me add; why the velocity profile is the same is because the surfaces have different charges, one being positive (slide 13) and the other -ve (slide 9) thereby influencing the flow direction (via charge distribution in the channel).

HAA_Contact Angle & Slip

haa69 — 2021-01-08 13:25:05 UTC

Contact angle is looked at in 3 ways (slide 5, like you mentioned). If you want to relate this to the slip/no slip behavior as explained in Lecture 3, then that will depend on the material used for chip fabrication. The application of an electric field to a hydrophobic material, will change its contact angle from slip to a no slip.
Example, Teflon is hydrophobic (non wetting), this contact angle of greater than 90 degrees can be lowered by applying an electric field (electrowetting) to change its behavior and make it less hydrophobic and therefore allowing the fluid to slid on it.

HAA_IPT 2 and 3

haa69 — 2021-01-08 13:25:11 UTC

The solution to IPT Questions can be found on Moodle

HAA_EOF in cylindrical Channel

haa69 — 2021-01-08 13:25:18 UTC

I fail to understand what the actual question is here.
Can you point out what exactly your question is?
I tried to understand it but all I can say is I am confused by this statement " wouldn't having a lambda D larger than the channel". How can Lamda D be greater than the channel?

Pls, if there is a typo, can you send back a reworded question? or just clarify to me what the question is.

HAA_IPT Recordings

haa69 — 2021-01-08 13:25:28 UTC

I have uploaded the solutions to the IPT questions.

EOF Valve

2021-01-08 17:05:19 UTC

Hi Haddy, thanks for the above response but I know there is no actual valve. I asked how it works as a 'valve' as there is still EOF flow to the right? In the lectures you say it works as a valve and there is no flow when back pressure = EOF flow, but in the velocity profile, there is still flow going towards the right near the walls. So surely it can't completely shut off the flow when working as a 'valve'?

HAA_EOF valve

haa69 — 2021-01-09 00:17:21 UTC

You are getting things mixed up.
How are you able to see flow from a 2D diagram?
Explaining its use as a valve is what you just did in your write up above.
Flow starts when you set it to.

NOTE this point!
It is within your control how you want to use EOF and pressure-flow depending on what the application requires. Just a pump or a valve or for mixing etc.

HAA_2019/20 nanoparticle

haa69 — 2021-01-09 01:02:02 UTC

Yes, the formulas in this question can be found in lecture 4.

As for the reaction kinetics, k and e are constants added to your equation, while k is given to you, e is just a mathematical constant (and can be found on your calculator).

The questions are simple, the added constants are just there to test your understanding of the applications of these topics.

HAA_EOF Pump and Scale-up

haa69 — 2021-01-09 01:02:22 UTC

I just had a look at the 2017/18 paper.
In this kind of situation, it was just an application question asking you how to scale-up in order to provide 1000 times higher flux.

The simple answer is to number up! or write a sentence like "a 1000x higher flux can be obtained by having n = 1000 parallel channels"

HAA_Scaling Question

haa69 — 2021-01-09 01:02:31 UTC

1) I think the confusion about scaling laws is that you are over thinking it!
To scale-up in microsystems, the approach is usually numbering up; except when you are asked to show how a parameter will be affected (which will be clearly asked if that is the case, therefore, you don't need to do any calculations).
So! for the answer to this exam question see "HAA_EOF Pump and Scale-up" above

2) 2017/16
First, every question should be approached based on what the question is asking. You can apply numbering up if the question warrants that.
In the case of Q.1c, the formulas you are using don't even relate to the question asked except at the end of option A where you stated the right formula and then you mixed it up again.

The right approach:
Q1c) Using scaling laws, discuss how you can reduce the elution time of analytes in electro-chromatography.

Note: t means "tau"

t=L/u_EO (Lec 4, slide 6)=L/u_EOE (Lec 7.2 slide 7) where u here is "miu" viscosity.

In terms of scaling laws t~l² and t~(1/E) where I is the characteristic length of the system. This means that elution time can be decreased using shorter columns and/or higher electric field .

HAA_Scale Up for EOF

haa69 — 2021-01-09 01:04:39 UTC

I thought my exams will be the 2020 paper? Have you seen it already?? :D

I will go for the latter, number up and hence voltage will remain unaffected.

HAA_2017/18 Q1)bi

haa69 — 2021-01-09 01:04:50 UTC

Q1) Assuming no other heat sources or sinks, or heat losses,
b(i) Calculate the increase in temperature across the channel generated by the applied electric field, with the inlet fluid at room temperature.

q₃ is not relevant for solving this question. You only need q₁ and q₂

HAA_Extra Problem Sheets

haa69 — 2021-01-09 01:05:34 UTC

Yes, I did mention that. I will upload them and email the class when I do.
Sorry I forgot!

I have uploaded them now.

HAA_L5-Practice Q2

haa69 — 2021-01-09 01:05:45 UTC

To use the overall heat exchanger flux is addressing it as a macrosystem because in macro heat exchangers, we use the LMTD (Log mean temperature difference) because looking at it diagonally/cross-sectionally, the heat at every point won’t be the same-right?.
In micro channels (in this case micro heat exchanger), it is not the case because it is instantaneous heat transfer due to the length scale.

HAA_Hydraulic diameter

haa69 — 2021-01-09 01:14:58 UTC

- Yes, when the channel is rectangular, you are expected to present your diameter as hydraulic diameter.

- You are also right about equating T_p = 1000 T_D(It is already given in the question)Then you calculate T_D from your T_p(because you have all the parameters to calculate T_p)
Next is to substitute for h in the equation for T_D(i.e. T_D=(h^2)/D_h)

HAA_2019/20 Paper

haa69 — 2021-01-09 01:15:08 UTC

Yes, it is.

HAA_Wetting Behaviour

haa69 — 2021-01-09 01:15:25 UTC

- A contact angle of >90 degrees means non wetting behaviour and this means there wont be a reaction at this interface.
- The aqueous phase would concentrate in the centre of the channel while toluene would coat the channel walls. A smooth interface would no longer be achieved and this will require the redesign of this reaction.
- However, looking at the given conditions, it would still be possible to produce nanoparticles but with a large size distribution due to the nonhomogenous interface between the two phases.

HAA_Y junction Microreactor 2019/20

haa69 — 2021-01-09 01:15:32 UTC

I am assuming this is the 2019/20 paper Q)di.
Pls, it will help me address questions more quickly if you point to the right place to look for your question and answer properly.

When you are asked such a question, it means you should calculate the minimum channel size (w=width) where you will get a good mixing/diffusion.

HAA_Model Answer

haa69 — 2021-01-09 01:17:10 UTC

Which paper do you need help with?

The questions covered in your IPT are also past questions and some of your LOILs too. And these were randomly picked in no particular order.

If you look at questions asked either in the lecture column or here in the interaction column, you will find answers to questions asked about past exam EOF.

HAA_2019/20 paper

haa69 — 2021-01-09 01:17:17 UTC

Yes, the answer to Q)ci is 1.6 sec

HAA_2017/18 Q1)bi

haa69 — 2021-01-09 01:18:55 UTC

1) Refer to my response HAA_2017/18 Q1)bi above

q₃ (conductive heat flux) is what you are leaving out. Pls, understanding the entire question is key to knowing what to consider or ignore.

2) For your second question, i will take the former i.e. velocity

- Look at question regarding this problem above "HAA_EOF Pump and Scale-up"

HAA_EOF Pump

haa69 — 2021-01-09 01:19:05 UTC

- By pushing (flowing) fluid using voltage controls, you are using it as a pump.

- The back pressure is maximum when there is no flow (Q=0) L7.2 slide 16

2017 /16 Scaling

2021-01-09 20:35:26 UTC

Hi, in the 2017 / 16 the question asks how we can use scaling laws to reduce the elution time. Is the correct approach to assume that the flowrate remains constant and to reduce the channel diameter to increase the velocity. Since the residence time = L/u this should reduce the residence time I think? Thanks.

HAA_Scaling

haa69 — 2021-01-09 21:36:26 UTC

It depends what the question is asking.

The formula you are choosing is correct, just try and continue to reason around your chosen formula and you will gradually have a grasp of how to approach the scaling questions.

Hint: They usually have short and straight forward answers.

Your answer to this question is above.

HAA_Past Paper Questions

haa69 — 2021-01-10 01:36:39 UTC

See column regarding this topic (EOF) and column for interaction to see how you can answer this question particularly and some other useful tips to scaling questions.

HAA_Scaling Law Slide 14

haa69 — 2021-01-10 01:54:51 UTC

Because we are now looking at it in terms of volume and volume relationship to characteristic length is l³.

2019-2020 Q1dii

2021-01-10 14:01:56 UTC

For minimum channel length, I get 15.8 cm. Surely this is too high for a microchannel? Not sure where I have gone wrong as the question is asking us to use the reaction rate coefficient provided, so our tau_P is fixed at 50 s.

In response to HAA_L5-Practice Q2

2021-01-10 14:17:14 UTC

Surely there are some occasions where the overall heat transfer coefficient needs to be taken into account? Please have a look at 2016-2017 and advise us on how we could solve part (d) without deltaTLM and part (e) without overall heat transfer eq.

HAA_2019/20 Q1)diii

haa69 — 2021-01-11 06:35:31 UTC

Your calculation is right. Just use this together with the instructions of the question to calculate your new residence time.

HAA_2016/17

haa69 — 2021-01-11 06:46:31 UTC

I think we have to narrow our thinking to microsystems and use what was taught in this course.
Please I will keep repeating, stop importing your knowledge of macrosystems into microsystems. Some will work and some wouldn't. Just go by what was taught and agree this is how these systems work!

d) How to approach it is still the same as my explanation above and as we did during the lecture (See solution sheet on Moodle).
I have corrected this question in class as I believe what the question is sought is t₁ and not t₂ because you end up with a higher value than the inlet. (Pls, see column 4 here under Heat Transfer and my response to the spotted error of this question)

e) You are only asked to calculate Reynolds number and discuss the implication of your answer on the column design; why are we talking about overall heat transfer eqn?

2018 Q1aii

2021-01-12 08:30:01 UTC

Sketch the velocity profile in a single channel for Qtot=0.

What type of velocity profile are they looking for? Is it this one?

EOF Mass Flux Scale Up Follow Up Question

2021-01-12 21:34:44 UTC

Hi Haddy,

I have read through all the responses here regarding scaling the EOF mass flux and there seems to be a slight contradiction. In some responses you suggest that this can be achieved by numbering up, while in others you stated the mass flux refers to the fluid velocity. However, the velocity could not be increased by numbering up (instead we would need to reduce the diameter as u proportional to 1/d^2, or increase the electric field).

Please could you confirm: when we are asked to increase the mass flux of an EO, which of these approaches is correct. Thanks.

HAA_L2 slide 19

haa69 — 2021-01-13 00:21:22 UTC

Yes, it is

HAA_Solution to practice question

haa69 — 2021-01-13 00:27:47 UTC

I have uploaded them now

HAA_Plasma

haa69 — 2021-01-13 00:27:55 UTC

This slide is just to help you know the concept and I am sure slide 23-25 of the lecture has an elaborate explanation to what plasma is including a video to explain further. watch it again, as nothing was skipped.
Plasma is a partially ionized gas composed of ions, electrons and other neutral species in ground and excited states.
To explain further, Sheath field is the cathode surface and this is where the substrate to be etched is placed.
The glow region of the plasma is the part that has a constant positive potential.

HAA_Disadv. of dry etching

haa69 — 2021-01-13 02:29:37 UTC

Loading Effect is the dependence of etch rate on the quantity of material being etched

HAA_LOIL 3 Exam Q

haa69 — 2021-01-13 02:29:53 UTC

It is a suggestion, you can design yours differently and justify it.

HAA_Fabrication Methods

haa69 — 2021-01-13 02:30:09 UTC

You can find your answer in the Q & A recording on Moodle.

HAA_Practice Questions

haa69 — 2021-01-13 03:22:27 UTC

I have uploaded solutions to practice questions under the lecture folder

HAA_

haa69 — 2021-01-13 03:35:34 UTC

Q_v means total volumetric flow while q_vis volumetric flow in each channel.
which means Q_vand q_v are the same thing. only that when you sum up a number of certain number of q_v it gives you a total Q_v.
So! what do you mean by keeping one constant and changing the other?

HAA_2018 Q1aiii

haa69 — 2021-01-13 03:39:41 UTC

No, not this one.
Qtot=0 means Peo max. The profile you have here is EOF with no pressure gradient (written on the far right of your image).

EOF Mass Flux Scale up

haa69 — 2021-01-13 03:54:18 UTC

In the exam papers, flux is being used in so many different ways. When I read a question and I help to answer it, I go with the context of the question and not generalize what was meant by flux as a parameter.
In your case, please state the question number and I can answer it correctly without assuming. I thought you were asking which is closer to flux (vel or Q) that is why I said it is better to use velocity.
The answer to 2017/18 Q1 c(i) is numbering up parallel channels to achieve 1000x higher flux.

2018-2019 Q1ci-ii

2021-01-13 05:14:05 UTC

For the 1st part, we are required to calculate the cross-sectional area
of frit. Is that just pi(a^2)? Also can you give the numerical answer to this question?

Also, for part ii, what application can we use the pumps for? I can't seem to find the relevant information in the notes.

2015-16 Paper Q1a

2021-01-13 09:14:36 UTC

Please could you go through this question in the revision session or please could you help clarify on here?

In the above response to "hydraulic diameter" you state that to find the height we use the below:

"Next is to substitute for h in the equation for T_D(i.e. T_D=(h^2)/D_h)"

Which suggests that you're using the hydraulic diameter on the denominator, Dh? Where has this equation come from? As in the notes T_D=(w^2)/D where D is the diffusion coefficient? Also in this question it already gives the width, so can the diffusion time also be related to the height?

deltaP/L Scaling

2021-01-13 13:37:17 UTC

Hi, you state that pressure drop scales with l^-2, however, the microfluidics textbook states that it scales with l^-4. Is this because you have derived it at constant velocity while they have derived it at constant flowrate? Thanks

2017 / 18 Energy Balance Clarification

2021-01-13 15:39:17 UTC

I've read the above responses regarding q1, q2 and q3. Please could you clarify, in the past paper you are saying we should ignore the conductive heat flux (q3) and this was the same in your example problem from lecture 5. Could I just confirm, is it always conductive heat flux we should ignore, and convective we should include? Also is there a textbook chapter or any material we could refer to for more information explaining why? Thanks.

2015 / 16 1 c

2021-01-13 16:16:10 UTC

Hi - what would happen to average nanoparticle size if the channel length is increased? I don't believe I've seen an equation for particle size anywhere. I know Td > Tp so more mixing would occur so potentially larger molecules but I can't quantitatively prove this.

2018-19 Paper Q1e

2021-01-14 19:14:14 UTC

Hi Haddy, please could you go through what method we would use to answer this question? I know people have asked similar questions above but I'm still not clear on the method. Would we be able to follow slide 8 lecture 5 when it asks for the scale up effects on h and L in an EOF pump? Even though in the lecture this was assuming just (Haagen-Poiseuille) pressure flow and in the exam questions we also have to consider EO flow?

Exam Paper 2016/17 Q1e

2021-01-14 19:32:03 UTC

Please can you explain how you would get the velocity of the cooling fluid to calculate Re without using the overall heat exchanger flux? You mentioned above that you wouldn't use h3 but please can you then explain how we would relate any of the information to the cooling fluid?

HAA_Questions above

haa69 — 2021-01-14 23:30:32 UTC

All questions here were addressed during LOIL session

HAA_2018/19

haa69 — 2021-01-15 01:03:57 UTC

- Yes, use Pi.r²
Q_eo = 1.48x10³ nL/sec
P_eo = 546.5 Pa

- base on the value of Qeo, we can use it for dosing and analytical applications

HAA_delta P/Scaling

haa69 — 2021-01-15 01:04:16 UTC

Like I have mentioned, we always scale with respect to the scaling factor.
In my example, our scaling factor was radius and you mentioned the textbook's scaling factor is flowrate. Obviously, we will get different answers.

HAA_Q&A answers

haa69 — 2021-01-15 01:04:22 UTC

All questions without an answer is because Dr Shahid has answered them in the Q&A session

HAA_2015/16

haa69 — 2021-01-15 01:04:30 UTC

You are right about potential growth of the particles and no need for quantitative proof. What the question is asking is what will happen base on an increase in the channel length.
Ans: This will allow interfacial reaction and the particle will continue to grow until it reaches the end of the channel.

HAA_2018/19 Q1e

haa69 — 2021-01-15 01:19:13 UTC

Yes, use the formulas on side 8 of L5 to approach the question.
Remember, the EO pump is also in a channel, so Hagen poiseuille applies.

HAA_Heat flux vs Amount of heat

haa69 — 2021-01-15 02:53:18 UTC

Can you clarify what exactly your question is here?

Lecture 3

2021-01-15 09:52:27 UTC

Can you use the continuum NS model in the slip region?

Reply to: 2018/19 Q1e

2021-01-15 11:32:53 UTC

Hi Haddy, thanks for your reply. Please can you explain why hagen-poiseuille still applies as in EOF we don't follow the hagen poiseuille flow rate equation? The flow rate of the EOF pump Q=Qeo+Qp ?

HAA_Slide 6 Slip regime

haa69 — 2021-01-15 16:03:04 UTC

Regarding the regime ranges, there is difference in the one on slide 6 and 7. Slide 7 has the graph and the picture at the bottom, only the Free Molecular Flow region has the same range for all 3. I will just advise you adapt one and use it to translate your result (different ranges from different sources). I will choose the graph if I have to select one.
For the class example, the whole calculation will change because I didn't convert the pressure from 1mTorr but rather used 1Torr.
For the regime choice as slip flow, most probably, I used the ranges from slide 6.
The kahoot question is correct. Why do you think it is wrong? Looking at the ranges from slide 6 or 7, continuum equation only apply at less than 0.001 or 0.01.

HAA_Slip Regime

haa69 — 2021-01-15 16:20:16 UTC

No, you cant use the continuum model for the slip regime except if the number falls too closely to the border of the regimes.

HAA_Q2

haa69 — 2021-01-15 16:20:23 UTC

Look at my explanation about the ranges on slide 6 and 7 in the response for "Slide 6 slip regime" above.
I did not select continuum, I said the continuum flow model can be used because if you look closely using the graph on slide 6 and 7, the value falls close to the border of both regimes (slip~0.01-1) and continuum (< 0.01).

2017/18

2021-01-15 16:58:15 UTC

Please can you explain why it is that we neglect q3?

HAA_Q1

haa69 — 2021-01-16 00:09:47 UTC

Yes

HAA_Lecture 3

haa69 — 2021-01-16 00:27:20 UTC

Only if the value falls too closely to the 2 boundaries

HAA_2018/19 Q1e

haa69 — 2021-01-16 00:28:27 UTC

As mentioned in the lecture recordings and relevant places, you will remember the formulas Q_eo and Q_p represents the expanded formula below. The highlighted formula is haagen poiseuille right?
I hope this answers your question.

haa69 — 2021-01-16 00:49:23 UTC

Good Luck in your exams!!

2019-2020 1d

2021-01-16 13:21:49 UTC

Hi Hadiza, in response to an earlier question, you said that the length was calculated to be 15.cm (for part ii). However, to calculate Re, should we not use 2w instead of w. If w is defined as the distance from the channel wall to the interface, then the diameter of the channel to be used in the calculation of Re should be 2w should it not? This would give a length of 0.079m.

Past paper 2018/2019

2021-01-16 18:08:43 UTC

Hi Haddy! could you please provide a model solution to Q1 bi of that paper please. Do we use q1+q2+q3=0 and solve for the temperature difference?

Thank you !!

Past Paper 2016/2017 question b) and c)

2021-01-16 21:41:45 UTC

Firstly, in part b how is elution time connected to Qt. Is it (1/Qt) * V of reactor? Or something else.

Next in part c can you explain how the scaling laws would work. Are we altering length or diameter. I suppose we keep length constant and continue scaling with D in order to reduce elution time.