Wireless Physiological Signal Tracking Bandage

Eric Vander Woude Author

04/02/2021 Added

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Spring 2021 Research Days presentation

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[00:00:00.690]Hello and welcome to the 2021 Research Days at UNL.
[00:00:04.010]My name is Eric Vander Woude, and I will be presenting
[00:00:06.460]on the wireless physiological signal tracking bandage
[00:00:09.520]in partnership with the Smart Materials
[00:00:11.590]and Robotics Laboratory, and Dr. Markvicka.
[00:00:14.770]First off, I'd like to acknowledge
[00:00:16.160]the John Woollam Foundation, NASA Nebraska Space Grant,
[00:00:19.110]and the Nebraska Tobacco Settlement
[00:00:21.630]Biomedical Research Development Center.
[00:00:25.530]Okay, so tracking bandages, why are they important?
[00:00:29.680]First off, we don't really have any ways
[00:00:31.800]to attract pandemic modeling or predict large scale illness.
[00:00:35.600]What this will allow us to do is get numerous data points
[00:00:39.050]and many people who can be tracked
[00:00:41.670]and also monitored for potential illnesses.
[00:00:44.390]Just like we see masks now
[00:00:45.890]that are starting to come out with smart masks,
[00:00:47.780]this would be another way to model
[00:00:49.530]and predict pandemic modeling.
[00:00:51.490]This can also be used in the medical field,
[00:00:53.210]an example, this neonatal area
[00:00:56.780]where it's a wireless bandage
[00:00:58.690]instead of having to be connected,
[00:01:00.280]where in many ways a normal bandage or patch like this
[00:01:05.020]would be hooked up to five, six, even maybe a dozen wires,
[00:01:08.470]which would then be connected to monitors
[00:01:10.220]instead of transmitting data wirelessly.
[00:01:12.360]This like this allows for
[00:01:16.230]not only the movement of this child,
[00:01:18.380]but also proper care in case something were to happen.
[00:01:21.140]So currently, we're limited by size and battery technology.
[00:01:25.210]So what we're working on this patch
[00:01:27.690]is first off the MAX30101 sensor,
[00:01:32.520]and what this does is takes heart rate and SpO2 data
[00:01:35.890]and can be worn and found
[00:01:38.430]in many numerous electronics that are currently worn.
[00:01:41.810]Some of these would be Garmin watches, Fitbits,
[00:01:44.560]and other devices like that.
[00:01:46.710]And what we're gonna do is partner with many other sensors
[00:01:50.630]to the point where you can get
[00:01:53.230]the entire physiological state of a human being
[00:01:56.120]by getting heart rate data, sweat data,
[00:01:59.860]potential organic compound exhalation
[00:02:02.430]and then also numerous temperature points around the body.
[00:02:07.340]So the first objective was to use NFC protocol
[00:02:10.300]and coils for data transfer and power transfer
[00:02:14.127]and the use of this allows for smaller coils
[00:02:17.320]to not only transfer data, but also be bifunctional,
[00:02:20.590]and then they would also transfer power,
[00:02:22.260]allowing us to use a smaller coil all around.
[00:02:27.090]Example can be seen on the right there.
[00:02:29.530]But what we found
[00:02:30.660]is that we would also need larger planar coils
[00:02:32.840]to be able to transmit power properly
[00:02:34.650]due to NFC's protocol not allowing for enough current.
[00:02:37.890]So these are a few examples of larger coils
[00:02:41.570]and this is an example of the circuit it would be,
[00:02:44.220]so when you're making a planar coil
[00:02:45.480]you have to keep in mind both the inductance and resistance
[00:02:48.910]and then the capacitances here
[00:02:50.630]are both parasitic capacitance.
[00:02:54.460]Okay, so in prepping the coils,
[00:02:56.930]what equation was used is down here on the left
[00:02:59.870]for our inductance,
[00:03:01.630]and then you have your equations there on the right,
[00:03:03.900]and then for measuring the values experimentally
[00:03:06.150]we would make the coils
[00:03:07.460]and then hook them up to an LCR meter
[00:03:10.670]and that would give us our inductance and resistance,
[00:03:12.920]both in parallel and series,
[00:03:14.280]depending on how we were setting up the coils.
[00:03:17.710]Testing them, we then connected them
[00:03:19.650]to a siglent waveform generator there on the right
[00:03:22.300]powering them for five volts peak-to-peak signal at 13.56.
[00:03:25.440]This is when we were still using NFC
[00:03:27.830]'cause 13.56 is NFC's natural frequency.
[00:03:30.890]And then we also hooked them up to an oscilloscope
[00:03:32.560]to view the current,
[00:03:33.830]and as you can see on the right here
[00:03:35.080]as you move the coils side to side, the current changes.
[00:03:40.190]Data transfer methods, we originally were using
[00:03:42.550]the nRF24 chip for data transfer,
[00:03:45.550]but it is a little clunky,
[00:03:47.060]so we're gonna try to go back to NFC for data transfer.
[00:03:50.390]And on the left there, if I play that,
[00:03:53.140]put your finger on the sensor,
[00:03:54.160]and there's an NRF chip here and there,
[00:03:55.930]and that's where it transfers the data through.
[00:03:57.830]And that's coming in here through Arduino,
[00:04:00.210]and then you got your IR value
[00:04:02.560]which is that red led sensor
[00:04:04.160]and then it just gives you your BPM and average BPM
[00:04:06.490]and those can then be recorded later on.
[00:04:08.810]And on the final right here,
[00:04:10.240]this is what the NFC setup would look like.
[00:04:12.310]The problem we're finding with NFC
[00:04:13.480]is that you can only read or write.
[00:04:15.780]It's hard to do both of them
[00:04:16.790]at the same time and communicate that,
[00:04:18.730]so that is a work in progress
[00:04:20.110]and something we'll continue to look into.
[00:04:21.670]Data visualization, we use Python and Arduino,
[00:04:25.520]so we program the microcontroller, the ATmega328P,
[00:04:30.432]and then we use Arduino for that,
[00:04:32.490]and then we would hook that up through serial
[00:04:34.620]and use Python to grab all the data
[00:04:36.480]off of the chip once it's done.
[00:04:38.730]And so there's an example of the output code here,
[00:04:41.470]so you can read, write, erase, and commands as need be,
[00:04:44.530]and then this is the text file that would be created
[00:04:47.590]when Python pulls in that code.
[00:04:49.250]So you can create that CSV file,
[00:04:51.980]we use spaces instead of commas currently to separate,
[00:04:54.780]or sorry, new line characters instead of comments
[00:04:57.090]just because a comma would be another character
[00:04:59.880]that we would then have to include data for
[00:05:01.610]and we have limited storage space on the flash memory.
[00:05:05.000]So miniaturization, this was originally
[00:05:07.600]on that large scale set up,
[00:05:08.660]what you saw on the left there earlier
[00:05:10.910]with the large Arduino and other sensors.
[00:05:13.470]Currently, we're working on miniaturizing this,
[00:05:15.420]we have our wireless charging chip here,
[00:05:18.480]flash storage, our 18 mega,
[00:05:20.370]and then our MAX30101 sensor,
[00:05:23.250]and this is the wireless charger
[00:05:24.690]that pairs with the coil here you see on the left.
[00:05:29.750]And so results,
[00:05:31.190]we found that just like normal
[00:05:34.272]your coil coupling end distance is a linear power ratio
[00:05:39.030]and so as you move further away,
[00:05:40.610]you're gonna be changing power.
[00:05:43.700]We found that circle coils work better than square coils
[00:05:49.120]when transferring power also.
[00:05:50.720]There's a couple other articles here at the end
[00:05:52.800]that you can reference for more data on that.
[00:05:55.390]Experimental data,
[00:05:56.590]currently, when we were trying to work
[00:05:58.500]with the miniaturization set up,
[00:06:01.120]we were finding that we weren't able
[00:06:03.700]to get the power we needed through the chip.
[00:06:05.820]And so after doing a little bit of analysis here
[00:06:09.300]over the last week and a half, two weeks,
[00:06:12.540]we haven't been able to finalize a new model yet,
[00:06:15.380]but we found that we are getting our five volts we need
[00:06:18.020]through our boot and AC1 capacitor.
[00:06:20.550]So that means that we are getting proper current
[00:06:23.900]and coupling through our coils.
[00:06:26.560]We just need to figure out
[00:06:27.630]if there's a short or another error in the circuitry
[00:06:31.470]up until the point where it goes
[00:06:32.670]into our lipo charger and then voltage regulator.
[00:06:37.833]So long-term data storage is possible at the sensor.
[00:06:42.460]That was all tested and completed and shown to be possible
[00:06:46.700]through our original breakout board setup.
[00:06:49.810]NFC protocol is unable to deliver
[00:06:52.470]the amount of current we need though for charging.
[00:06:54.772]FOD communication needs to be the same protocol,
[00:06:57.590]which we're thinking could also be a potential problem
[00:07:00.750]with that charger if I go back here two slides.
[00:07:03.134]This charging chip that's on here
[00:07:05.410]is not the same charging chip
[00:07:07.980]that is on our actual transmitter for wireless charging,
[00:07:11.560]so we'll need to check that.
[00:07:13.330]And then also adding wireless charging
[00:07:14.970]does increase the device greatly
[00:07:16.240]rather than just having plug and play,
[00:07:17.890]but we are gonna be encapsulating this in elastomer later
[00:07:20.310]so it does need to be wireless,
[00:07:21.550]so that is why we have that.
[00:07:23.580]Future work, this will all become a flexible PCB,
[00:07:26.150]which will then be surrounded in elastomer,
[00:07:28.200]and we'll cover the bottom elastomer
[00:07:29.570]with a ferrite glycerin material
[00:07:32.390]to help add a ferrite shielding,
[00:07:34.080]which will also increase
[00:07:35.140]the coupling co-efficient of our coils.
[00:07:37.130]And then finally we're gonna test
[00:07:38.670]the highest charging speeds while not overheating
[00:07:42.110]and explore other methods data transfer
[00:07:44.300]as in connecting to phones, apps, and things like that.
[00:07:48.240]So thank you so much and have a great rest of your evening.

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Wireless Physiological Signal Tracking Bandage

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