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3 Emerging Applications for Sensor Technology in Wearable Medical Devices

June 17, 2019
These days, wearables are being associated with much more than just frivolous fitness pursuits.

When one hears “wearables,” it’s easy to dismiss the phenomenon as nothing but flashy fitness trackers or sleek smart watches, but in the burgeoning world of health tech, new devices are pushing the boundaries—not only of imagination, but also of science.

From simple step-counters to devices that use pulse oximetry or even the composition of one’s sweat, the new generation of wearables uses sensors in combination with AI and Machine Learning to improve, and sometimes even save, lives.

Take, for instance, the opioid epidemic in the U.S., which is estimated to be claiming more than 115 lives a day. Opioids are vastly overprescribed. Some estimates hold that for every 100 Americans 58 opioid prescriptions are written, a problem that has led to drastically increasing levels of addiction, overdose, and death.

This epidemic has caused a veritable public health crisis, with both the public and private sectors scrambling for solutions, from taking steps to cut initial prescription rates to helping those already addicted. In May 2018, the FDA even launched its own innovation challenge hackathon to crowdsource creative solutions to the problem, receiving more than 250 applications.

Wearables Save Lives

One of the winning devices in the FDA’s challenge was a wearable wristband created by students from Carnegie Mellon University called the Hope Band.

Made to be worn by at-risk addicts, the Hope Band uses pulse oximetry which shines light from LEDs through the skin, while sensors work to pick up changes in light absorption—a predictor for oxygen levels in the blood and the most reliable indicator of an overdose.

If the device detects that oxygen levels have dropped to dangerous levels, it will first continue to monitor for an additional 10 sec. to rule out a false reading, after which, if overdose is still being predicted, the band will sound an alarm along with flashing lights. It can also be paired to a smartphone, which would call emergency services or alert a contact person in the case of a detected overdose. This early-alert system could enable first responders to administer life-saving naloxone, a drug which reverses opioid overdose effects.

The Carnegie Mellon team admits it still faces numerous challenges. For a start, it can only currently test the device on animals, as testing it on overdosing humans is illegal. Secondly, vitals vary from user to user, so the team is hoping in its next iteration to apply better Machine Learning algorithms to its data to improve the prediction accuracy. One would imagine that a third difficulty might be getting addicts to wear the band, or not have it stolen from them by other addicts looking to sell them.

Other wearable devices that emerged from the FDA’s challenge do things like stimulate the brain with magnetic fields with small chips placed behind the ear, emitting electrical pulses to stimulate branches of certain cranial nerves. Depending on which nerves are stimulated, these devices could help block pain or other challenging withdrawal symptoms when one is trying to wean themselves from opioids.

The Hope Band.

For Parkinson’s Patients, Constant Monitoring and Tremor Reduction

While drug addiction is arguably a self-inflicted issue, other health conditions being revolutionized by wearables are not.

Parkinson’s Disease (PD), for example, which affects over 1.2 million Americans and more than 10 million people globally, has also seen some helpful breakthroughs in the world of medical technology—mainly in diagnosis and monitoring of symptoms, but also in helping to alleviate the condition.

Most of the technology used in PD research uses sensors like accelerometers and gyroscopes to capture data which often help to improve PD diagnosis, something which is still not easy to do through regular clinical examination.

Ongoing monitoring of symptoms is also particularly helpful as doctors often don’t see patients for extended amounts of time and must, therefore, rely on their patient’s anecdotal reports.

Wearable sensors, however, can relay mostly reliable information on an ongoing basis, even uploading data immediately to the cloud, so that doctors can make adjustments to medications or treatment plans accordingly.

Wearables can also help patients stick with prescribed exercise programs and remind them of when to take their medications.

For ease of use, they can be worn on the wrist, trunk, or even ankle, and like most wearables, they can be paired to a smartphone for extra functionality. Some researchers find that soft wearable sensors —adhered to the skin and able to move flexibly—are even more useful than rigid wearable bands, as they allow for greater flexibility in sensor placement and are sometimes less of a hindrance to their wearer.

Some devices already on the market measure bradykinesia (slowness of movement, one of the cardinal manifestations of PD) and dyskinesia (involuntary muscle movements) through measured set time periods.

Big tech firms like Microsoft have also dabbled in prototype wearables for the PD space, not just for monitoring, but for helping to lesson symptoms. In 2017 the firm unveiled Emma’s Watch, a device named after a young British graphic designer and PD sufferer, Emma Lawton, which uses vibrating motors to diminish tremors. Lawton herself reported a dramatic improvement in her writing ability thanks to the device, which is still under development.

A further advantage of setting up PD patients with wearables is that a much larger data set can then be collected globally, helping clinical trials and research for future treatments immensely.

Blood, Sweat, and Tears

Even sweat can now be monitored by wearable devices for various benefits, including (rather bizarrely) powering your phone.

An article in the Journal of Energy and Environmental Science last year discussed a stretchable textile wearable with an in-built hybrid supercapacitor–biofuel cell (SC–BFC) system for soaking up the wearer’s sweat and converting it into useable energy, then storing it for later use. Apparently, the biochemical energy from the sweat can be oxidized enzymatically, which produces the energy in question, which is then stored in a module which uses MnO2/carbon nanotube composites “that offer high areal capacitance and cycling electrochemical stability.”

Other sweat-based wearables measure concentrations of electrolytes, and can even test for things like cystic fibrosis and diabetes.

To do that, sensors and microprocessors are adhered to a person’s skin to form a miniaturized iontophoresis interface which then stimulates the sweat glands with an electrical current. Once sweat is excreted, it’s processed to detect the presence of various molecules and ions which can be detected based on different electrical signals.

For example, if a high level of chloride ion were to be detected in the sweat, there’s a high probability that the wearer could be suffering from cystic fibrosis. If high levels of glucose were measured, this would be a good predictor for diabetes.

Because the sensors are so accurate, a very full picture of a person’s health can be built up out of tiny amounts, potentially enabling a future of highly targeted and personalized medical care, as well as a gauge of how well people respond to various medications, vitamins, exercise regimes, and more.

So, while it may remain true that “clothes maketh the man,” wearable devices, too, have an increasingly important role to play—one that not only helps a person monitor their current state of health and track their own progress, but builds a future where future generations may benefit from flexibility in sensor placement the analysis of current wearable data on a massive scale.

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