Use of ph or glucose probes to diagnose compartment syndrome

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 27th - December 3rd Alex Goodman: Research/Progress Summary Met with Dr. Doro and discussed final design and deliverables Expressed concerns about glucose quantity being too miniscule to detect with our dexcom sensor Suggests we create solutions with much high concentrations This sunday, we plan to make a 100, 500, 1000, and 2000 mg/dl to ensure we have enough glucose to detect Issues/Dilemmas Waiting for circuit completion so we may begin creating final deliverables Advisor Meeting Agenda Discuss requirements and expectations for final deliverables Poster examples? What should we highlight in our presentation? Kristina Geiger and Carly Rogers: Research/Progress Summary We constructed the PBS/Glucose solutions before Thanksgiving break, and intended on using them for testing on the Sunday before Thanksgiving break, however; we could not get the circuit to function, so we will be using them this weekend to calibrate and test the circuit/code that Will and Heather made The final protocol that we wrote before Thanksgiving break is going to be used during testing to ensure our probe is accurate, durable, and can measure the glucose when

2 inserted through two mediums. This protocol can be found in the lab archives, but it may be tweaked based on trial and error during testing. During our last client meeting this week Wednesday, we discussed with Dr. Doro our progress on the project, and he offered us his opinions and some ideas for testing Dr. Doro suggested that we use several different solutions to confirm our device works in more than just one solution. Some suggested solutions were water and glucose, saline and glucose, PBS and glucose, gatorade, and orange juice. We should be using chem sticks to confirm the glucose concentrations of these solutions so we can guarantee the accuracy of our device and improve the calibration Dr. Doro also suggested that we use a bigger range of glucose concentrations to test our device so that we are able to show definite differences in concentration between solutions. He feared that our original chosen concentrations were too low and too close together to get substantial data that shows our device works, so he suggested to test with big jumps in glucose concentration such as 100 mg/dl, 300 mg/dl, and 500 mg/dl. We will still calibrate our device with the original lower concentrations Issues and Dilemmas: We realize that 100 mg/dl, 300 mg/dl, and 500 mg/dl glucose solutions are not the desirable concentrations for this device to be reading. This device theoretically will be used to measure glucose concentrations below 100 mg/dl, however; in this initial stage of testing, we just want to be able to prove that our device shows a difference in concentration. We will have to make it clear that further along in the future, it would be necessary to scale down these concentrations that the device detects in order for it to be purposeful. In order for us to perform any testing on our device, we need the circuit to be functional first. Agenda: Discuss with Professor Block our issues with the circuit and our progress since before Thanksgiving break Discuss with Professor Block our new testing ideas Discuss with Professor Block what needs to be done before our final presentation Make our circuit functional, and perform the final testing Summarize our data and project progress, and input this information into our final deliverables Heather Barnwell and Will Bacon:

3 Research Summary This week we worked on the circuitry of the device and met with Professor Nimunkar to discuss possible arrangements of the circuit, we will meet again with him on Friday to discuss the conclusions of the possible circuit diagrams that we will research Thursday night to compile for our meeting Many DIY potentiostat circuits exist which have inconsistencies between them, we plan to research these, pick a few potential candidates, and get one approved by Professor Nimunkar before we build Our current method is shown below where the reference electrode and working electrode have a constant difference of 300mV to fuel the reaction on the glucose probe. The counter electrode measures the current and converts it to be read by the arduino as a voltage to be calibrated. The concept behind this potentiostat was to supply a constant potential difference between the reference and working electrode. This potential difference would power the redox reaction at the working electrode surface that would in turn produce a current in the counter electrode that could be measured The current from the counter electrode was ran through a transimpedance amplifier to convert it into a voltage to be read into an analog input on the Arduino Uno microcontroller. Figure 1: Original Circuit Diagram. A constant 5V digital output from the Arduino runs through a voltage follower and inverting op amp to reach the desired output voltage of 300 mv. This voltage is applied across the reference and working electrode. Finally a transimpedance amplifier converts the input current from the counter electrode into a voltage to be read by the Arduino.

4 Figure 2: Overall Schematic of a potentiostat Figure 3: This is a potential candidate for our final circuit The above circuit varies from our original circuit We will ground the working electrode to the same ground as the Arduino Uno. From there we will apply a mv potential to the reference electrode with respect to the Arduino s ground. This effectively means that the working electrode is mv with respect to the reference electrode.

5 Issues/Dilemmas The voltage was reading even when the circuit and op amp wasn t powered, leading us to believe that either the op amp was compromised or that the circuit was wrong We created voltage followers to test how the 2 op amps were working and this revealed that the LM324 and TLV272 were working The arduino also broke and wasn t uploading or powering anything, since we only had one arduino on hand, we weren t able to test the circuit with another The electrodes may have been too far apart from each other in the solution Agenda We plan to meet with Professor Nimunkar again to discuss our options of different circuit diagrams for a potentiostat Our task for Friday is to continue researching potentiostat circuits Our team will reconvene on Sunday to complete testing and calibration