3D Printed Stethoscope Makes the Grade

On the off chance that initiatives like the Hackaday Prize didn’t make it abundantly clear, we believe strongly that open designs can change the world. Putting technology into the hands of the people is a very powerful thing, and depending on where you are or your station in life, can quite literally mean the difference between life and death. So when we saw that not only had a team of researchers developed a 3D printable stethoscope, but released everything as open source on GitHub, it’s fair to say we were pretty interested.

The stethoscope has been in development for several years now, but has just recently completed a round of testing that clinically validated its performance against premium brand models. Not only does this 3D printed stethoscope work, it works well: tests showed its acoustic performance to be on par with the gold standard in medical stethoscopes, the Littmann Cardiology III. Not bad for something the researchers estimate can be manufactured for as little as $3 each.

All of the 3D printed parts were designed in OpenSCAD (in addition to a Ruby framework called CrystalSCAD), which means the design can be evaluated, modified, and compiled into STLs with completely free and open source tools. A huge advantage for underfunded institutions, and in many ways the benchmark by which other open source 3D-printable projects should be measured. As for the non-printed parts, there’s a complete Bill of Materials which even includes links to where you can purchase each item.

The documentation for the project is also exceptional. It not only breaks down exactly how to print and assemble the stethoscope, it even includes multi-lingual instructions which can be printed out and distributed with kits so they can be assembled in the field by those who need them most.

From low-cost ultrasounds to truly personalized prosthetics, the future of open source medical devices is looking exceptionally bright.

[Thanks to Qes for the tip]

22 thoughts on “3D Printed Stethoscope Makes the Grade

    1. perhaps their printer was very slow? Anyway, making tools like this or actually making tools like this available for cheap can be a lifesaver for many underdeveloped countries. Although the real question is, if they have access to a 3D printer, they have the tools and technology to do this. But if they don’t, then how do they get these devices, shipment and distribution are perhaps almost as challenging. Making sure that the tools get to the right people and that they use them what they are intended for (using them in medical situations and not for trading).
      Anyway, the first step in solving these problems is having a tool to print/distribute/use and this step has been made with this project, so well done.

      PS: I had hoped to read some more details about the development, why it took so long to make it “perfect”, what were the designs challenges that made it took so long and now that the project is finished… how will it go further from here?

    2. I’m not sure making a good stethoscope is quite as simple as it seems. The principal appears straight forward, but if you’ve ever used a really cheap one you’ll know the difference. You can already buy a commercially made stethoscope for less than the $3 quoted here, from a proper medical supplies company so not literal toys ones. These are the kind of thing hospitals stick on their wards for when doctors forget where they put theirs down (something you quickly learn to be more careful about after you’ve lost your first one), but they aren’t intended for serious use – here you’re expected to supply your own decent one.

      So maybe 3 years of work has managed to make something that’s actually good, certainly they claim to have, and that’s great for the third world but I’ll stick to my Littmann. I don’t know how many third world doctors will have access to a 3d printer though, but perhaps if there is something about the design of these that makes them as good as an expensive one someone will mass produce them and sell them cheaply.

      1. I know next to nothing about stethoscopes but I have a couple of questions on how they are used.

        First I will describe how they appear to be used from the perspective of me as the patient:
        The stethoscope is applied at various points on the back or the chest while the patient is directed to breathe normally/deeply/cough/etc

        Some questions I have:

        * How are doctors trained to use them? How does a teacher communicate or describe the characteristics of a sound to a pupil, and what it means? Or is the learning opportunity erratic in the sense that the pupil has to wait until a person with the ‘right’ affliction passes the hospital, in order to hear the anomaly? Or do teachers have audio recordings to play to the students?

        * What is the role of varying the different positions of stethoscope application? What kind of information is gleaned from changes in sound with changes in position?

        * Can you envision utility in the ability to digitally record stethoscope audio, i.e. to send a recording to colleagues, or some domain expert for their opinion? Or for recording rare/bizarre sounds that are hard to classify? Or for recording sounds that could be easily misclassified for features that are different but deceptively similar sounding?

        * Is there an exhaustive listing/classification/reference on stethoscope usage?

        * Do you think the simultaneous recording by using multiple stethoscopes on different points at the same time allows for more information to be gleaned, or perhaps more accurate determinations to be made?

        The reason I ask is because it seems trivial to replace the earpiece with a closed chamber with a microphone, and to perhaps put some slightly attenuating foam or sponge in the tube, just like the attenuating (by design) transmission line from probe to oscilloscope (to avoid reflections). The low price could allow multiple stethoscopes in the same device for applying at the different points at once.

  1. Wow. This could easily be adapted for mechanical uses as well. Have a look at your run of the mill automotive stethoscope and the only real difference comes down to the end making contact with the engine. It’s just a meal rod you touch to the mechanical device’s casing and a plastic chamber with a plate inside.

  2. I thought it was a neat build but it really only achieves it’s target price if you build them in bulk. You have to buy a lot more material than you need to make one. It makes me wonder if an electronic model might not be more efficient in terms of making just one. A similar head but it houses a condenser mic. On the front of it a second chamber that has a small pdb that holds the amp IC and batteries, and a jack for plugging the headphones into. Might cost $6 or $7 but that would be in one off quantities and it would use disposables (batteries).

    1. sorry… the patient has died… as I clearly can’t hear his heartbeat.
      Oops… it wasn’t the patient… only the batteries were dead.

      Sorry, but the beaut of the stethoscope is that it is one of those device that doesn’t need electricity to function and therefore ALWAYS works. Combined with the absence of complex circuitry make it very reliable.
      But also because there are already enough devices with disposable batteries… we don’t need another one.

    2. I’ve been told electronic steths are heavily patented and doing research on the patents is a minefield. Also their acceptance among the medical community is not great.

  3. Or maybe a “horn” to funnel (and isolate) the sound into a phone’s mic, similar to phone camera lens adapters, with an app to capture it. The app could do simple triage analysis (heart mostly, but maybe also lungs). The recorded sounds could be sent to real medical Dr/nurse/tech (but soon, we won’t have enough of them for our aging population) or AI on the Cloud for expert analysis.

    A simple ECG could do the same and maybe more for heart issues (e.g. AD8233) and maybe able to do double duty for brain injuries (EEG).

  4. Although I have no use for the stethoscope itself, it’s a worthy and useful project. I am often interested in perusing the open source code used to generate the result in the hope I will always learn something new. In this case, looking at the OpenSCAD files.

    However after doing that, what surprises me is that three years in development was not enough time to go through the code and define some meaningful variable names for the many values used. It’s chock-full of magic numbers everywhere. The beauty of parametric modelling is precisely that – parameters. If someone wants to modify this design they are going to have to forgo the use of a customiser and instead figure out the magic numbers for themselves, comments notwithstanding.
    Having a TUBE_DIA = 5 or statements to that effect would really help.

    1. It’s yet another example of engineers not taking a step back, handing their thing over to someone who knows absolutely zero about the product – then watching for all the trouble the person has trying to figure it out, or how they find ways to make it fail. The engineers know about those issues but due to their complete knowledge of the product they unconsciously never ‘trip’ them.

      See the 1st generation iPhone 4’s antenna gap in precisely the wrong spot – for everyone except the people who designed it and thus wouldn’t place their finger across it.

      1. Yes I saw the Ruby code, and after another look found printable_stethoscope_head1_assembly.rb which has some definitions, but these are embedded directly as arguments in the function calls. Maybe I’m missing something but the Ruby code just seems to me to add an extra layer of cruft and complexity when OpenSCAD is (from my experience) quite capable of handling that itself.

  5. Also, What happened to that $5 dollar Blu-ray laser diode mosquito sensor and zapper? You know the one that had the backing of the Gates foundation. The one they did videos on. And showcased 2.5 pages in Wired magazine. ?_?

  6. I wonder how much variability there is in the build quality? I’d bet a lot will depend on the printer’s mechanical state.

    For sure, it shows this is a viable way to produce a stethoscope. If I were doing lots, I’d be looking at ways the tubes could be moulded rather than printed, but the design is right.

    It’d be interesting to hear from Littmann how a $3 device is able to match their offerings too. Maybe more stringent testing? Who knows?

    1. That sounds like a pretty interesting idea, stethoscopic logger as opposed to a diagnosis tool.
      Colds, influenza, … most of these conditions are diagnosed, and the patient is prescribed rest, and simply waiting it out. Perhaps by logging stethoscopy we can more objectively measure/quantify the influence of room temperature, drugs, or food, or behaviours (blowing out the nose versus just cleaning away the snot dripping out), sleeping on the side or on the back or with the back tilted at various angles. Compare the anomalous sound characteristics (when does the disease stop, or how often or long or loud one coughs etc) with those for a control group.

      Perhaps we can objectively find better ways of treating or advising self-treatment for common small diseases.

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