Flexible, Thin-Film Biosensors

We like to keep a pulse on the latest biosensor research going on around the world. One class of biosensors that have really caught our attention is the so-called thin-film sensors, pioneered by the Rogers Research Group at Northwestern University.

We’re no strangers to the flexible PCB here at Hackaday. Flexible PCBs have become increasingly accessible to small-scale developers and hobbyists, explaining why we’re seeing them incorporated into many academic research projects. The benefit of these types of sensors lies in the similarity of their mechanical properties to those of human skin. Human skin is flexible, so matching the flexibility of skin allows these thin-film sensors to adhere more comfortably and naturally to a person’s body.

The circuits used in these thin-film sensors are what we’ve grown accustomed to. An instrumentation amplifier to measure heart rate (and oftentimes respiratory rate) from the electrocardiogram, a light-emitting diode, and photosensor pair to measure heart rate, respiration, and blood oxygen from the photoplethysmograph, a thermistor or non-contact infrared sensor to measure temperature, and an accelerometer to measure activity. Really the beauty behind what the Rogers group has done lies in their flexible PCB design. They’re strategically using serpentine interconnects between modular components of the PCB, allowing the circuit to bend and fold in predetermined locations. All that’s left is some good low-modulus silicone to cover the electronics and give the device a nice, soft-to-touch surface, adding to the comfort level of the user.

Really, this strategy is no different than what we’ve explored here at Hackaday, and we’re happy to see others finding utility in flexible PCBs as well, especially for medical applications. We like to think that maybe the Rogers group has been inspired by the many creative projects that have graced the front page of Hackaday and hope that you are inspired to keep on hacking as well.

6 thoughts on “Flexible, Thin-Film Biosensors

  1. These look wireless too, which MASSIVELY increases usability. One of the banes of nicu/scbu/paed HDU is negotiating all the lines and wires when cuddling/feeding/changing/caring for the child. Another life changing tech thats always been in my head is a drip pole that follows the kid around as they run around the ward. Those things are akin to tethers if theres nobody to push the pole around.

  2. Much of that sensing can be done non-contact using a camera and image processing.

    Definitely heart rate and breathing, possibly even blood oxygen level (from skin color of lips). Temperature can be done remotely with an IR sensor.

    The image processing requires a lot of computation, and I don’t know if anyone is making a medical stand-alone unit that does this, but it seems like it would be a better solution.


    1. Only question there would be accuracy. If the flexible PCB has 5% error and the camera has 15% medical is going to pick 5% almost every time. You compound that with this being targeted at NICU and it’s almost guaranteed whatever is the most accurate will get picked.

    2. My child spent a few weeks in the NICU, and I agree with the non-contact naysayers. We had a well-equipped hospital, which contained a mobile computing station for each room for the staff to use, but these would require upgrades before being able to accomplish image processing.

      Also, using image processing to determine the temperature of a small moving target that could be moved around the room (e.g., skin to skin time) and sometimes require external heat lamps and/or their bed unit lid to be closed(when newborns cannot properly regulate their temperature), this seems like it would induce much more error.

      I am excited to see what new tech comes out in this area, but pray that you never have to see its use.

  3. Congenital heart defects are the #1 birth defect on the entire globe. These babies undergo palliative staged repairs that require often month long hospital stays. The sensors with five pounds of wire harness were hard to bear after our son’s three open heart surgeries. These sensors are what I dreamed of and am glad to see this creation!

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