Semester 2- Week 4 Kierstin

 

*Back pressure (or backpressure) is a resistance or force opposing the desired flow of fluid through pipes, leading to friction loss and pressure drop. 


Calibrating the pressure sensors: 

How to test pressure in the small tubing/ Benchtop Plan:

Pictures 1-4 were taken when Alex and I worked with Dr. Rickard to figure out the pressure sensors. We read the data sheet and then connected it to our system to get the pressure values. We labeled the wires to make it easier to connect and disconnect, as well as to replicate when we need to add more pressure sensors to the benchtop test. We calibrated the sensor to ensure it was working, and then we took measurements of the voltage at different heights to create a linear graph. Using this linear graph we were able to calculate the pressure in mmHg. When Alex and I did it the first time it was with the wrong connecting wires, so we remeasured using the wires shown in the pictures above. (This is shown in the excel pictures above) 

Brinkley and I redid the test of measuring voltages at different heights to get the linear equation. We used this equation to get the pressure in mmHg. We used Excel to calculate our values and ran tests at different eye pressures, and used different suture resistances to get some base data. This is what picture 5 shows. Picture 6-8 is the manufacturing of the valves. The purple needles are used to cut holes in the valves and insert the tubing and the scissors and scalpel are used to make the valve thinner. We coated the outside of the valve with a soft epoxy to try to seal the insert points of the tubing so there wasn't any leakage. We also poured more molds for prototype manufacturing.

In this excel sheet, you type into the purple boxes and then the white boxes are calculated. 

We worked on manufacturing more small valves. Picture 9 shows two flawed prototypes. One tube fell out on the bottom one, and the top one was cut too deeply when trying to make it thinner, so the epoxy cover blocks the flow. Picture 10 shows us using 2/0 nylon sutures as resistance to measure the pressure in the shaved tubing. 

These are the recorded values of the pressure sensor at varying eye pressures and with varying suture resistances. 

In SolidWorks, I created new valve molds to work on our prototype and have more spares for when we are manufacturing them. The top row is the correct length and width dimensions, and the bottom two rows are slightly wider, but the correct height. This is because we will use those to practice manufacturing. 


Dr. Rickard noticed that the units in the drawings were incorrect, so I had to go back into Solidworks and change them from inches to mm. This took a little bit because I did not remember how to change the units on the page, so I ended up just manually changing it rather than finding where it would change it to mm on every drawing I make. 

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