This Week's Team Meeting

Hey all! So this week, I got together with the rest of the team for the pressure sensor to discuss what our next steps were to complete the sensor. And I actually found out a couple of more details for the pressure sensor I didn't realize were needed: one being all the necessary components to assemble the pressure sensor. I was missing a part of the pressure sensor. It is a 6X6 board, with drill nuggets in the center of each square. This will be put on top of the printed circuit board when we start testing the sensor. The purpose of this board is so the lab has something to test whether or not each sensor on the printed circuit board will detect the same amount of pressure as it should.

I didn't think of it at time, but I should of took a picture of the board. But hopefully at this upcoming meeting on Monday I'll be able to. Not much beside the meeting happened this week though. I worked more on my power point presentation, which was a good thing. My professor told me more materials for printing circuit boards came in this week, and I'm hoping that this upcoming week I'll be able to contact a team member for them to teach me and do some fabrication. The ultimate goal next week is to assemble the pressure sensor. All I need to do is contact people in the group and commit to a set date that we can assemble it and test it as well.

That's all for this blog, sorry it's so short! Until next time!


- Tina Smith

Printed Circuit Board Fabrication

This was the week guys! I finally got to learn the whole printed circuit board fabrication process. Of course I had some ups and downs trying to get here, scheduling wise, but I did it nonetheless. Today I met with my on-site mentor Dr. LaBelle to discuss the process. From this meeting, I learned that there is actually two ways to create a circuit board: the old fashioned way and the new way. In his lab, he does both. But he likes to start off newbies, like myself, with the old way to get a better understanding of it all.

Now what is the old fashioned way and the new way? The old fashioned way just means a circuit board is created chemically, while the new way is done by a machining. Since I didn't do the machining fabrication, I know very little about that process. Dr. LaBelle did tell me, though, that a machine strips off the copper for the circuit board; and that this process is standardly used now a days due the process being faster and able to produce fine details onto the circuit board.

So now onto the chemical fabrication process. I will tell you ahead of time that these steps came from Dr. LaBelle's lab. Just like the screen printing process, he puts these directions and these pictures in his lab so his students know what the process is when they do it. This isn't what the circuit board for the pressure sensor will look like, it will look like the design I put in a previous blog. All credit goes to Dr. LaBelle's lab for these pictures and steps! He graciously gave these to me for my update during our meeting so I could have a visual aspect to this blog. Since I couldn't take pictures while I watched the demonstration (I left my phone in my backpack).


STEP 1
Place mask on top of pre-sensitized board after blacking type is removed and place into light box

* Setup etchant tank. For a 6' x6'' board, make 437.5 gm of sodium persulphate to 1.75 L ddH20 (warning pH 1.0). Stir well for 15 min. Fill etchant tank, place bubbler on and heater unit (next to bubbler) and set at 6.0 for1/2 hr and turn down to 4.75 which yields 40 C


STEP 2

Remove mask after 2 min UV exposure

* If using UV light box. Set time to 120 sec. Place PCB onto glass, cover with artwork, turn VAC on and leave on (VERY IMPROTANT) during exposure!! Note: board will not change color at this step.

STEP 3

Remove exposed photoresist with sodium hydroxide and scrubbing for 1-2 min.
Wash board with water to stop developer.

 * While developing, add 40ml of sodium hydroxide developer solution to 360 ml ddeH20 (warning pH 14.0). And pour onto board in plastic tub (glovers needed for developing an etching steps). Gently scrub the board using sponge brush for 1.5-2min to remove the exposed photoresist so that the design is left in green photoresist surrounded by copper. Rinse the board using water to stop developing.

STEP 4
Etch board in ammonium persulphate for 10 min to remove exposed copper

 *The final removal of the copper is done during agitated etching in an sodium persulphate solution for up to 15 min (can take 30 min sometimes). As soon as all the copper on the exposed area is removed, remove board and rinse in water to stop etching. The board will be a greenish yellow with the design in photoresist.

STEP 5

Wash board with warm tap water for  > 30 sec to stop etchant and immediately engrave numbers

*Individual electrodes (or strips) will be cut out form the PCB with a slow speed, fine tooth band saw. The final photoresist can be removed with acetone rinse to expose the copper for electroplating. Otherwise store with photoresist left on

So there it is, the fabrication process of circuit boards. Again, I'd like to thank Dr. LaBelle for allowing me to use these pictures and directions. It took him and his lab a long time to get the fabrication process correct for the printed circuit boards (years he said). If you guys have questions, comment in the comment section below. Until next time!



- Tina Smith

What I Have Learned So Far

Entering my few final weeks at ASU, it has dawned on me that my project is getting closer and closer to ending. It has also dawned on me how much I've learned in the past 5 or so weeks during this internship. I'm now comfortable in a biomedical engineering lab setting; and although it isn't something that I specifically learned under the guidance of my on-site mentor, I still feel that it is a great accomplishment to achieve. It has pushed me to re-evaluate what I want in a university. And that push led me to research my top list of schools under the criteria of research funding and innovation.

In addition to this re-evaluation , I've learned that the things I feared most in engineering is what intrigued me pick it as my major, and my project. It is all about physics and mechanical work. Screen printing, printed circuit board fabrication, materials design, and circuit board design all fit under what I have learned at my internship. My project is also about learning how one does research. And I've concluded a lot of it has to do with waiting and practicing patience. In my last blog, I said I was waiting to learn printed circuit board fabrication because we needed new materials. Unfortunately, those materials didn't come in this week. So that means I haven't fully learned what the fabrication process entails. But I'm hopeful that this week will be the week to start learning.  This doesn't mean I did nothing during this week though. I actually split most of my time working on my powerpoint draft and reading about the fabrication process.

Below is a site that I came across that I really liked. On the side of the website, it divides the process into parts. If you click it, it will tell you the different part in that process. Some of those parts have different articles attached to them that discuss that specific sub-part of the fabrication step. Some part of this website are still being put up, but overall I thought it was a good start to the learning process.

http://www.pcbfab.com/


I'm know this week sounded really boring, and I'm sorry for that. But hopefully the next blog will be more exciting.  Until next time!



- Tina Smith

Waiting...

Hey guys! I now this is kind of a late post, but this week has been a bit hectic for me. I needed to work a lot at my part time job, in addition to going to ASU, and I had family birthdays to plan for. Although hectic, this week was mostly a transition week for me at my internship. Since ASU was on Spring Break last week, it seemed like this week people in the lab were getting back in the grove with things. So I spent a lot of time at the library this week, reading and designing new things for the circuit board.

Currently I'm working on a new revision of my design for the printed circuit board. I needed to make a little adjustments after talking with my on-site mentor. I need to make sure the spacing between the wirings are each 0.1 inch apart. In addition to that I needed to add pin connectors for each of the 6 wires in the 6X6 matrix. This is so we can measure things during testing. I'm still working on that revision for that, which I will hopefully complete on Monday. After I finish it, I will post a picture at the end of this blog for all of you to see.

Next blog I will be discussing the fabrication process of the printed circuit board that I will be learning sometime next week. I don't know any of the specifics of this process yet, so if you have any questions I hope to be able to answer them in the next blog.

It's Getting There

Hey guys! I know most of you  guys are on spring break, so this will be a short post about my week. Since I took off a few weeks ago, I still needed to go into ASU to get my 15 hours. And let me tell you, the ASU campus during spring break is dead. By observation, it seemed the only people on campus were the graduate students. As my sister put it, "There are no breaks in a life of a graduate student, including mine."

Not much happened this week in terms of my new project. The group I'm working with is slowly getting everything together so we can finish making this pressure sensor. The only thing I did this week was research the wires the lab and I are going to use for the circuit board. Why you ask? Because I need to know the spacing between each wire. Why do I need to know the spacing between each wire? Don't I just get 12 wires and create a circuit board? No. Before I would have though that, but in reality the wires come in a long strip. And each long strip has a bunch of wires. Since the lab is using a flexible wire type, I need to research online the spacing to edit my circuit board design.  In my last blog, I put a picture of my circuit board design. So if you haven't seen it, you should go check it out. On my design, there is a total of 12 lines in that photo, and therefore 12 wires for the circuit board. It was important for me to know what the spacing between each of those wires needed to be, to ensure there was enough space on the board, and that the wires wouldn't touch.  From researching online, the spacing between each of the lines needed to be 0.1 inch apart. Knowing that, the lab can put in an order online (or go buy it in a store if it is available) to speed up the production line.

So that's about all that happened this week. Not much hands on experience, but hopefully in the next coming weeks, the project will be complete and we can start different testing with the pressure sensor. Hope you guys are enjoying your spring break! Until next time!


- Tina Smith

A Change in Direction

This past week has been busy, busy, busy! Not only did the direction of my project change, but I was also brought together, once again, with an old nemesis of mine: Physics. Confused? Ok, let me take a step back and tell you what happened with my project. On Tuesday February 24th, I went into Dr. LaBelle's office to discuss what I was going to be doing in the lab that week. When I stepped into the office, he said he found a project for me to work on. In my head, I'm like, "Ok. Cool. I can do this. Wait, will I know anything about the topic?" Notebook in hand, I sat down and got to taking notes. And here I met my nemesis, Physics. Throughout the entire conversation, the only words I got across my mind from my 3 pages of notes were pressure sensor and circuit board design.  So after that meeting, I went straight to my sister-- who previously worked on this project-- to ask her to explain the entirety of the project.

MY NEW PROJECT

My new project is to build a pressure sensor with a team of other individuals in the lab. Now what is a pressure sensor? Exactly what is sound like, it is an instrument that detects changes in pressure when someone applies it. It can calculate pressure and then one can look at the contour of pressure over a certain area. Of course, I'm not making the entire thing. So what is my part in this project? Well, earlier I said I understood 2 outcomes from the meeting I had with Dr. LaBelle: a pressure sensor and a circuit board design. And the later is my designated part in the project. I am to make a circuit board design for the pressure sensor.

What does a pressure sensor look like? Now I could describe it to you, but then things get far too confusing and wordy. Instead I will show you. Below are pictures of a previously made pressure sensor. Now the pressure sensor I am working on will have a different design of the cooper wiring you see below. The wires will be much much smaller and more of them.

This is a 6x6 model of the pressure sensor. As you can see there are a lot of wiring sticking out everywhere, which is a challenge the lab is trying to fix.   

This is the bottom of the pressure sensor.

As you can see the lab had to attach wires to each cube of the 6x6 for the circuit to be complete.
(This is the underside of the picture above)
 

This is the middle layer of the pressure sensor. It is nonconductive foam. Within in each cube there is a circle cut out so the lab could put conductive foam in, this is to ensure top and the bottom circuit board would connect.  

This week I spent a lot of time with Dr. LaBelle reviewing and redesigning the wires. Below is the final copy of what the circuit board design will look like. It may not look like it took a long time to make, but I assure you it took a solid 2 hours of my time to get the correct number of lines, spacing, and configuring done. But that's what happens when you aren't tech savvy I guess.   

I'll show you guys the final product once the lab and I finish it! If you guys have any questions, ask in the comment section below. Until next time guys!

- Tina

PS. I wanted to send a special thanks to my sister who helped me out a lot this week. Especially when I would ask her such silly and out of the blue questions when she had to do work. THANKS VICKI! <3

What is Screen Printing?



Hey guys! I know this is early in the week, but this is a post to explain the process of screen printing. A few people two weeks ago asked what exactly the screen printing process was, and I wanted to hold off answering that question so I could post this blog. I know what some of you are thinking right now, "this post is late, late, LATE!" And that I didn't post last week. But last week was technically my week off (I had to go to Texas Wednesday through Saturday and couldn't go to the lab to get all my required hours). I started working on this post last week, and I'm sorry that is so long. But there was a lot I wanted to talk about and share with you guys. So here it goes! :) 

What is screen printing? And how does one make screen printed electrodes? Well, screen printing is a technique in which an individual uses a stencil to spread ink onto a surface to get a desired design. And in my case, the desired design would be an electrode. In my previous post, I compared the screen printed process to baking. So I will continue using that analogy and list the "ingredients", steps, and baking time of each part of the screen printing process. So let's start, shall we?

First off, here are the materials needed in this process.

Materials Used

1. Stencils                        

2. Conductive carbon ink

3. Conductive Sliver        

4. Oven                             



                           

 Below is an outline of the screen printing process in the lab that I intern at. Dr. LaBelle created this so his students would know where the stencils of each part are, as well as know the steps of the process so no confusion ensues. Now I'll break each step down for you.

Step 1and 2  

Before I start the process, I go to the oven and set it to 100 degrees Celsius (it takes a really long time to bring the temperature up to that mark).

 So in the first step, I take the stencil #1 --which looks somewhat like a bunch of trees-- and put it on printer paper. Then I take the conductive carbon in, a black, thick substance, and spread it on the stencil. During this process, I make sure to keep a constant pressure spreading the ink across the stencil. This is to ensure each electrode made (the stencil makes 4) have the same amount of ink and bake properly.

Now I head over to the oven, place the paper with conductive ink on a metal rectangular sheet, and put it in the oven. And I bake it for 1 hour.

Here is a closer look at the stencil I used in step one.

Here is a closer look at the stencil I used in step one.

Here is the product of step 2

Step 3

Step 3 is exactly the same as step 2, except with a different materials. I use conductive silver, instead of conductive carbon ink; and I use the stencil shown below, instead of the one above.  I still scoop up the silver and use constant pressure when spreading it across the stencil. The most difficult part of this task is lining up the stencil on the electrode, and making sure the conductive silver doesn't run off due to its liquid form. After that, I go back to the oven and bake it for 1 hour at 100 C.

I need to line the stencil up to lines 3, 6, 9, and 12 of the electrodes.

Step 4

After step 3, I must now take the insulating ink and repeat what I have been doing for the past 3 steps. I take the stencil, line is up, spread the ink on, and then bake it for 1 hour in the oven.  

Insulating ink is a lot stickier than the previous inks, so I need to be careful spreading it on so that the stencil won't move while I spread it onto the stencil.

Step 5

 I know by now you think the screen printing process sounds really tedious. And you probably already know the next step I have to do: the same as step 4! I must complete my insulating circle on the electrodes by doing the same exact thing as step 4 and bake it for an hour. 

And finally, after 4 hours, I have my screen printed electrodes. So there you have it, the screen printing process. If you guys have any further questions about it, just ask in the comment section bellow. Until next time guys!

- Tina Smith