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As people increasingly strive to carefully quantify each action, the sensors that monitor them are becoming lighter and less invasive. Two sensor prototypes from Stanford and Berkeley rivals compete in the skin and provide a wealth of physiological data.
Stretchy Stanford's "BodyNet" is not only flexible to survive worn on the changing surface of the body; this flexion is where his data comes from.
The sensor consists of metallic ink placed on a flexible material such as an adhesive bandage. But unlike phones and smartwatches, which use tiny accelerometers or optical tricks to follow the body, this system relies on how it is stretched and compressed. These movements result in minimal changes in the way electricity goes into ink, changes that are relayed to a processor located nearby.
Of course, if you place a label on a seal, like some of these electronic stickers, it can indicate if and how much this joint has been flexed. But the system is sensitive enough to detect the slight changes that the skin feels during each heartbeat or the larger changes that accompany breathing.
The problem comes when you have to get this signal of the skin. Using a wire is annoying and certainly very '90s. But the antennas do not work well when they are flexed in odd directions – the efficiency drops off, and there is very little power initially – the skin sensor is powered by the signal collection RFID, a technique that makes the voltage path very difficult.
<img class = "breakout aligncenter size-full wp-image-1870000" title = "bodynet_sticker-and-receiver" src = "https://techcrunch.com/wp-content/uploads/2019/08/bodynet_sticker-and- receiver.jpg "alt =" bodynet and receiver sticker” width=”1024″ height=”683″ srcset=”https://techcrunch.com/wp-content/uploads/2019/08/bodynet_sticker-and-receiver.jpg 1500w, https://techcrunch.com/wp-content/uploads/2019/08/bodynet_sticker-and-receiver.jpg?resize=150,100 150w, https://techcrunch.com/wp-content/uploads/2019/08/bodynet_sticker-and-receiver.jpg?resize=300,200 300w, https://techcrunch.com/wp-content/uploads/2019/08/bodynet_sticker-and-receiver.jpg?resize=768,512 768w, https://techcrunch.com/wp-content/uploads/2019/08/bodynet_sticker-and-receiver.jpg?resize=680,453 680w, https://techcrunch.com/wp-content/uploads/2019/08/bodynet_sticker-and-receiver.jpg?resize=50,33 50w” sizes=”(max-width: 1024px) 100vw, 1024px”/>
The second part of their work is that of the receiver, which collects and retransmits the sensor signal to a telephone or other device. Although they have managed to create a unit that is light enough to hang on clothing, it's still not the kind of thing you would want to wear in the gym.
The good news is that this is a limit in terms of engineering and design, not theoretical – so it takes a few years of work and progress in the electronics field to get a lot more system attractive.
"We believe that someday, it will be possible to create a network of skin sensors covering the entire body to collect physiological data without disturbing the normal behavior of a person," said Professor Zhenan Bao, a professor at Stanford, in a press release.
Over at Cal is a project in a similar field that aims to move from prototype to production. Researchers in the country have been working for a few years on a perspiration monitor capable of detecting a number of physiological factors.
<img class = "breakout aligncenter size-full wp-image-1869999" title = "Sweat sensor on the front" src = "https://techcrunch.com/wp-content/uploads/2019/08/SensorOnForehead_BN.jpg "alt =" BN SensorOnForehead” width=”750″ height=”500″ srcset=”https://techcrunch.com/wp-content/uploads/2019/08/SensorOnForehead_BN.jpg 750w, https://techcrunch.com/wp-content/uploads/2019/08/SensorOnForehead_BN.jpg?resize=150,100 150w, https://techcrunch.com/wp-content/uploads/2019/08/SensorOnForehead_BN.jpg?resize=300,200 300w, https://techcrunch.com/wp-content/uploads/2019/08/SensorOnForehead_BN.jpg?resize=680,453 680w, https://techcrunch.com/wp-content/uploads/2019/08/SensorOnForehead_BN.jpg?resize=50,33 50w” sizes=”(max-width: 750px) 100vw, 750px”/>
Normally, you collect sweat every 15 minutes or so and analyze each lot separately. But that does not really give you a very good temporal resolution – and if you want to know how sweat changes minute by minute or less? By putting the systems of collection and analysis of sweat on the skin, you can do it.
Although the sensor has been in the works for a while, it's only recently that the team has begun adopting large-scale user tests to see what sweat measurements have to offer.
<img class = "alignright wp-image-1869997" title = "RollToRoll_BN-768×960" src = "https://techcrunch.com/wp-content/uploads/2019/08/RollToRoll_BN-768×960.jpg" alt = "N ° of roll 768×960″ width=”384″ height=”480″ srcset=”https://techcrunch.com/wp-content/uploads/2019/08/RollToRoll_BN-768×960.jpg 768w, https://techcrunch.com/wp-content/uploads/2019/08/RollToRoll_BN-768×960.jpg?resize=120,150 120w, https://techcrunch.com/wp-content/uploads/2019/08/RollToRoll_BN-768×960.jpg?resize=240,300 240w, https://techcrunch.com/wp-content/uploads/2019/08/RollToRoll_BN-768×960.jpg?resize=544,680 544w, https://techcrunch.com/wp-content/uploads/2019/08/RollToRoll_BN-768×960.jpg?resize=40,50 40w” sizes=”(max-width: 384px) 100vw, 384px”/>"The goal of the project is not just to make the sensors, but to start doing many studies on the subject and see what sweat tells us – I always say" decode "the composition of sweat. For this, we need reliable, reproducible sensors that we can scale to fit multiple sensors in different parts of the body and apply them to many subjects, "said Berkeley professor Ali Javey. and project leader. .
As anyone who works in computer hardware will say, switching from a hand-made prototype to a mass-produced model is a huge challenge. The Berkeley team therefore called upon his Finnish friends at the MTB Technical Research Center, who specialize in roll-to-roll printing.
Roll-to-Roll is an excellent technique for flat and relatively simple electronic components. It basically consists of printing the sensors directly onto a flexible plastic substrate, which we can then simply cut to the desired size. In this way, they can manufacture hundreds or thousands of sensors quickly and inexpensively, making them much easier to deploy at arbitrary scales.
This is not the only flexible or skin-mounted electronics project, but it is clear that we are approaching the time when they start to leave the lab and head to hospitals, gyms and homes.
The paper describing Stanford's Flexible Sensor was published this week in Nature Electronics, while the Berkeley Perspiration Tracker featured in Science Advances.
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