Cornell Students Have Your Back

Back problems are some of the most common injuries among office workers and other jobs of a white-collar nature. These are injuries that develop over a long period of time and are often caused by poor posture or bad ergonomics. Some of the electrical engineering students at Cornell recognized this problem and used their senior design project to address this issue. [Rohit Jha], [Amanda Pustis], and [Erissa Irani] designed and built a posture correcting device that alerts the wearer whenever their spine isn’t in the ideal position.

The device fits into a tight-fitting shirt. The sensor itself is a flex sensor from Sparkfun which can detect deflections. This data is then read by a PIC32 microcontroller. Feedback for the wearer is done by a vibration motor and a TFT display with a push button. Of course, they didn’t just wire everything up and call it a day; there was a lot of biology research that went into this. The students worked to determine the most ideal posture for a typical person, the best place to put the sensor, and the best type of feedback to send out for a comfortable user experience.

We’re always excited to see the senior design projects from university students. They often push the boundaries of conventional thinking, and that’s exactly the skill that next generation of engineers will need. Be sure to check out the video of the project below, and if you want to see more of this semester’s other projects, we have you covered there too

21 thoughts on “Cornell Students Have Your Back

  1. They could combine that with a TENS Machine and activate the back muscles to align the spine as part of a control loop. It would eventually cause the relevant muscles to be stronger and you would be less likely to slump even without the device on. However making it wireless could lead to people getting their back hacked and being forced to perform unusual dance moves in public. :-)

    If anyone knows where I can get 2 axis flex sensors (with the same shape) please let me know because I actually have an orthopaedics project starting now that could benefit from them. Lower legs not spine, and it is for children so it needs to be compact and robust.

    1. Love the feedback idea. I’d probably buy one of those, I’m a horrible lower-back sloucher.

      You could just mount the flex sensors at right angles to each other. That said, mounting these things robustly is actually a bit of a pain, because they kind of want to break between the hard plastic backed section and the pins. Best solution I found was sewing them into a tight little channel in something you wear.

      Also, I know a guy who used this same sensor to make a “male arousal meter” that was used in some psych research. I’ll give you one guess how that worked.

      1. Merging two of those flat sensors may not work if they stop each other from bending in the same way an I beam works, even if they are offset.

        I think I may need to build stacks of foam segments then I’ll have direction of flexure, amount and position along the sensor, unless it is a product you can buy?. We are talking about a lot more data too, so the A2D input will need an analogue multiplexer chip in front of it.

        1. I need something like this image below.

          The area between the segments would contain a firm but flexible material. The blue lines select the segment and the other lines select the layer, so as you can see it would give you a lot more data. Each segment is not a flex sensor but a pressure sensor, so even conductive foam may be all that is required, the trick is to fabricate the entire flex-sense-tube so that it is only 10 mm in diameter. After all that is does tell you how much it is flexing, but in a different way.

          1. Like clear tubing filled with a gel, and strain gauges printed along it’s outer length and circumference. One stretching and it’s opposite in compression.

          2. @Ostracus Well that is another way to do it, but does it give you 8*8 scannable points of measurement, or just 8*1? You can extend the diagram above so that there are 8 discs. If you split the discs and unwrap the tube you get one way to potentially simplify fabrication, there are many ways to go about it and optimising that would be a fun project in itself.

          3. Polyvinylidene fluoride is piezoelectric, and they used to make it in a sensor form called Kynar. It was basically a thin sheet of plastic that was aluminized on both sides. The piezoelectric activity was huge – you could easily get 100+ volts from stressing the material (at almost no current).

            I’ve got some experience using these – they’re pretty easy to work with. They give a signal while being flexed, and settle down when still, so you’d have to integrate the signal to get absolute position. Also, there’s no way to get any sort of fine resolution because the amount of signal is dependent on the exact stress and motion at the time, which varies with the position on the limb and speed of flexure and other variables. You get resolution from having multiple sensors, and only roughly one or two bits of precision of speed and flexure.

            You’d have to get some from a manufacturer, but for a good cause they might give you some samples.


            Kynar is used in all sorts of medical places such as dental X-ray film holders (the thing that goes in your mouth), so I think it’s GRAS for medical purposes.

  2. Cool project! I was actually planning on making (still planning mind you) the same project using the same type of sensors! Although I think some sort of vibration motor would be cool and maybe some data that’s collected and sent to your phone so you can review it.

  3. “These are injuries that develop over a long period of time and are often caused by poor posture or bad ergonomics”

    Oddly enough poor abdominal muscles contribute as well.

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