Advisor Meeting Agenda Discuss our circuit design process this 9:30 pm with advisor

Transcription

1 Use of ph or glucose probes to diagnose compartment syndrome Client : Dr. Christopher Doro Advisor : Professor Walter Block Team : Alex Goodman Team Leader agoodman4@wisc.edu Kristina Geiger Communicator kgeiger4@wisc.edu Heather Barnwell BSAC hbarnwell@wisc.edu Will Bacon BPAG wbacon@wisc.edu Carly Rogers BWIG crogers6@wisc.edu Date: November 6th - November 12th Alex Goodman: Research/Progress Summary Currently waiting for all parts to arrive so we may begin constructing our circuit Although it will be created and tested in controlled lab area, this construction will provide a valuable first step Meeting with team this Sunday 11/11/17 to discuss circuit design and possible signal processing schemes Heather and Will will spearhead the issue, as they have taken BME 310 and have instrumentation experience Issues/Dilemmas More issues will arise next week when we actually build the device Advisor Meeting Agenda Discuss our circuit design process this 9:30 pm with advisor Kristina Geiger & Carly Rogers: Research/Progress Summary The past week, our team has been waiting on materials and formulating ideas for the circuit for our probe, because of this, not much has changed for our testing methods We have decided once again that we will be using PBS solution for a second round of testing of our sensor. Dr. Doro was concerned that our probe would not act the same in a solution of saline and glucose as it would in PBS solutions, and so he wants to make sure this is not true by also running calibrations in PBS solution. However, we can make this with materials from the school s wet lab. PBS was used in testing of the sensor we are using

2 We can make this before testing begins Here is the link to the methods to make a PBS solution, and Alex, Heather, and Will also know how to make this from their previous project We have three tentative testing methods: Pure diluted glucose solution: beakers with d-glucose from the school and distilled water. This will be run as a baseline for testing accuracy of the probe with the epoxied tip and circuits we built. We will simply be inserting the probe into the solution to take a reading and then record it We will have varying concentrations of glucose to test the accuracy of the probe at high, low, and average concentrations of glucose PBS and glucose solution: beakers with fabricated PBS solution with chemicals from the school. As stated above, Dr. Doro really wants to mimic interstitial fluid as close as possible. We will follow an almost identical procedure that we used for the baseline glucose testing. Steak and Sponge: Put a soaked glucose sponge on top of a steak of known volume marinated in a known glucose concentration. The reason this experiment was brought into our plans also goes along with more closely mimicking a human compartment. It was brought up at the meeting that calibrating our probe to 100% solution is most likely not going to be an accurate representation of what a human compartment enduring trauma is going to be like. This would mean that the steak needs to be marinating in a glucose concentration for an extended period of time (three hours to a day were time periods discussed). We acknowledge the fact that the streak may already have glucose in it, but for our purposes we are going to assume that the concentration after marinating the steak is going to be equal to the concentration we are exposing the steak to. Further: We will make it so that the steak and sponge are at different glucose concentrations to make sure our sensor is reading the correct data (The steak glucose concentration, NOT the sponge). We have began to develop the details of our testing methods such as dilution processes, protocols etc. that we will need to use after the probe has been made/modified. Issues and Dilemmas: We need all of our materials to come in and our probe to be fabricated before we can start the bulk of our testing, which will not give us a lot of time before the end of the semester to run these tests.

3 We ordered the sponges through Dr. Doro, so we are waiting on these Waiting so long to run tests will not give a lot of time to actually run them or make changes based on the first round of testing. We also may not have time to get to all of our prepared tests. Agenda: Discuss our different methods of testing Discuss if we need to alter our current methods Discuss what we can be doing in the meantime while we wait until we can start main testing Heather Barnwell: Research Summary The past week, we have waited for the parts to arrive and they have been arriving for the past couple of days so soon we will be able to start fabrication Will and I will focus on the circuit for the device We have both of our electronics kits that we will be able to use together including Arduino, resistors, capacitors, potentiometers, etc. Since the signal is expected to be very low, we should use an op amp or even a series of op amps to enhance the gain of the signal Op amps produce a voltage that is larger than the original and decreases noise If Rf > R1 then larger gain More specifically, we can use a differential amplifier like the one pictured below

4 The differential amplifier takes voltages from 2 inputs and gives the proportional differences between V1, V2 In our case V1 will be the wire in the body, and V2 will be the reference Issues Dilemmas The setup will not look sleek, it will most likely be a jumble of wires so we should consider getting a covered box so that the connections aren t loose It will most likely be very touchy if it is not housed properly The electrical signals coming from the wire will most likely be low and data will be completely based off of experimental data, since there aren t sources that define the electricity from the glucose reaction Agenda Discuss circuitry as we expect to run into problems when we work on it Sunday night Focus on fabrication of circuit since this will be the toughest part Update gantt chart/schedule Will Bacon: Research Summary Most of the parts that we have been waiting for have now arrived, so we will be able to begin fabrication of the electrode and circuit We will start by fabricating the working electrode by elongating the sensor portion of the Dexcom sensor using silver epoxy We will then create the reference electrode/counter electrode by making a Ag/AgCl wire out of a silver wire using the protocol on World Precision Instruments website. ( ) For the circuit, we will use a similar setup detailed in the image below.

5 In our case, the reference and counter electrode will both be combined in the AgCl electrode that will be wrapped around the outside of the working electrode. A voltage from a potentiostat, found in the design rooms in ECB, will be able to supply the voltage across the AgCl electrode and the Pt electrode to begin the enzymatic reaction. The resulting current from the reaction will be converted into a voltage with the help of an op amp, capacitors, and resistors. Finally the voltage will be read into an Arduino, which will convert the voltage to a glucose reading using an experimentally found calibration factor. Issues/Dilemmas I can t find any data on what voltage should be supplied to start our enzymatic reaction, since we don t know exactly what chemicals were used in the sensing portion of the Dexcom electrode. Miniaturizing this will be difficult given our limited electrochemical background, so for now we will focus on making the circuit functional. Advisor Meeting Agenda Discuss general circuitry setup

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