How To Monitor Blood Pressure Without Raising It

Does anyone actually enjoy the sensation of being squeezed by a blood pressure cuff? Well, as Mom used to say, it takes all kinds. For those who find the feeling nearly faint-inducing, take heart: researchers at UC San Diego have created a non-invasive medical wearable with a suite of sensors that can measure blood pressure and monitor multiple biochemicals at the same time.

The device is a small, flexible patch that adheres to the skin. So how does it manage to measure blood pressure without causing discomfort? The blood pressure sensor consists of eight customized piezoelectric transducers that bounce ultrasonic waves off the near and far walls of the artery. Then the sensor calculates the time of flight of the resulting echoes to gauge arterial dilation and contraction, which amounts to a blood pressure reading.

This patch also has a chemical sensor that uses a drug called pilocarpine to induce the skin to sweat, and then measures the levels of lactate, caffeine, and alcohol found within. To monitor glucose levels, a mild current stimulates the release of interstitial fluid — the stuff surrounding our cells that’s rife with glucose, salt, fatty acids, and a few minerals. This is how continuous glucose monitoring for diabetes patients works today. You can check out the team’s research paper for more details on the patch and its sensors.

In the future, the engineers are hoping to add even more sensors and develop a wireless version that doesn’t require external power. Either way, it looks much more comfortable and convenient than current methods.

Wearable Sensors On Your Skin

An international team at Penn State led by [Larry Cheng] made a breakthrough in printing sensors directly on skin without heat. The breakthrough here is the development of a room-temperature sintering technique. Typical sintering of copper happens at 300 C, and can be further lowered to 100 C by adding nanoparticles. But even 100 C is too hot, since skin starts to burn at around 40 C.

You can obtain their journal article if you want the details, but basically their technique combines the ingredients in peelable face masks and eggshells. With this printed circuit is applied to the skin, the sintering process only requires a hair dryer on the cool setting, and results can bend and fold without breaking the connections. A hot shower will remove the circuit without damaging the circuit or your skin. [Larry] says the circuits can be recycled.

They are using these sensors to monitor temperature, humidity, blood oxygen levels, and heart performance indicators. They’ve even linked these various on-body sensors with a WiFi network for ease of monitoring. After reading this report, we’re left wondering, if the sensor is directly on your skin, can it be really called wearable?

We’ve written about printable inks before, but for printed circuit board applications.  We can’t help but wonder if this technology would help solve some problems inherent in that technology, as well. Thanks to [Qes] for the tip.

Souped-Up, Next Gen Wearables

The biggest hurdle to great advances in wearable technology is the human body itself. For starters, there isn’t a single straight line on the thing. Add in all the flexing and sweating, and you have a pretty difficult platform for innovation. Well, times are changing for wearables. While there is no stock answer, there are some answers in soup stock.

A group of scientists at Stanford University’s Bao Lab have created a whisper thin co-polymer with great conductivity. That’s right, they put two different kinds of insulators together and created a conductor. The only trouble was that the resulting material was quite rigid. With the help of some fancy x-ray equipment, they discovered that adding a molecule found in standard industrial soup thickeners stops the crystallization process of the polymers, leaving them flexible and stretchy. Get this: the material conducts even better when stretched.

The scientists have used the material to make both simple, transparent electrodes as well as entire flexible transistor arrays with an inkjet printer. They hope to influence next generation wearable technology for everything from smart clothing to medical devices. Who knows, maybe they can team up with the University of Rochester and create a conducting co-polymer that can also shape-shift. Check out a brief demonstration after the break.

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Conductive Circuit Board Tattoos: Tech Tats

While hardcore body-hackers are starting to freak us out with embedded circuit boards under their skin, a new more realistic option is becoming available — temporary tech tattoos. They’re basically wearable circuit boards.

Produced by [Chaotic Moon], the team is excited to explore the future of skin-mounted components — connected with conductive ink in the form of a temporary tattoo. And if you’re still thinking why, consider this. If these tattoos can be used as temporary health sensors, packed with different biometric readings, the “tech tat” can be applied when it is needed, in order to monitor specific things.

In one of their test cases, they mount an ATiny85 connected to temperature sensors and an ambient light sensor on the skin. A simple device like this could be used to monitor someone’s vitals after surgery, or could even be used as a fitness tracker. Add a BLE chip, and you’ve got wireless data transfer to your phone or tablet for further data processing.

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