Wearable medical sensors are getting better

Researchers are working to improve health monitoring by creating wearable sensors that collect data for clinicians while limiting discomfort for patients

Penn State researchers are working to improve health monitoring by creating wearable sensors that collect data for clinicians while limiting discomfort for patients.

Penn State engineer David Cheng has developed wearable head scanners, needle-free glucose monitors and more. The sensors are capable of monitoring patients’ physical motions and chemical signals in their sweat, skin and more to help diagnose or inform treatment plans. They are made with flexible electronics and self-charging electronics.

Facebook’s Meta Reality Labs has awarded Cheng $150,000 to advance wearable technology. Biodegradable, stretchable, energy-generating systems will be developed. There’s a need for environmentally-friendly, self-charging sensors that can monitor patients’ vital signs.

Self-powered, rechargeable wearables

Self-charging power units for stretchable energy harvesters already exist, but are heavy and expensive. Graphene-based materials, however, are light and tiny. When correctly shaped, graphene can harvest energy from motion, and store it as electrical energy in micro-supercapacitors.

Cheng and his colleagues used this technique to create a self-powered, stretchy health monitor made of porous graphene foam. The details were published in Applied Physics Review today.

Self-powered sensors can measure vital signs such as pulse, electrocardiogram, blood pressure and oxygen levels. Sensor doesn’t require a wired power supply or a charger. Firm’s sensor could eliminate wired sensing entirely using Bluetooth or radio transmission of data in the future.

The self-powered, wireless medical sensors get their energy from the user’s kinetic motion. The micro-supercapacitors, which monitor the user’s actions and create a cyclical charge for the device, are powered by this energy. Credit: Larry Cheng group, Hebei University of Technology, Xiangtan University. All Rights Reserved.

The method might be used to track the movements of wildlife such as bats or seals, in addition to human applications, according to Cheng. The device can be recharged indefinitely by the animals’ motions.

“We combined numerous of our prior breakthroughs to create this whole system — but we’re not done yet,” Cheng explained. “We want to make each component of these systems as cost-effective, long-lasting, and resilient as feasible.”

In this spirit, Cheng and his colleagues have recently published two articles outlining advancements in more efficient, cost-effective, and renewable approaches to improving sensors and their applications.

From tissue paper to pressure readings

A wearable sensor that detects blood pressure and respiratory conditions is made from tissue paper. The device is created by dipping a piece of tissue paper into conductive material, which is then pressurized to create a 3D scaffold and encapsulated to become a sensor that sticks to the skin.

The wireless gadget is worn on the forearm and measures the dilatation and constriction of a blood vessel in the wrist to determine blood pressure. It’s a lot smaller and easier to use than a traditional blood pressure monitor, which employs a cuff to keep pressure on an arm for a single reading, according to Cheng.

This wearable sensor is made by dipping a piece of tissue paper into conductive substance, then pressurizing it to form a 3D scaffold, which is then encapsulated to form a sensor that attaches to the skin. On the back of the hand, pressure readings can be taken and transferred to a smartphone. Credit: Larry Cheng group, Hebei University of Technology, Xiangtan University. All Rights Reserved.

“A blood pressure cuff in the hospital wakes patients up when they’re attempting to sleep,” Cheng explained. “This technology would enable for round-the-clock remote monitoring.”

The device collects data on blood pressure, heart rate, and cardiac activity, which may be relayed to a doctor via a Bluetooth smartphone app.

“Pressure-based manufacturing is simple and inexpensive,” Cheng remarked. “After the device is decommissioned, all of the materials, including the silver in the sensors, can be recycled, and they are easily available.”

The sensor is light enough to be comfortable while yet being sturdy enough to withstand jogging or sweating. The sensor was also integrated into a face mask to allow researchers to remotely monitor respiratory variables, including potential irregularities, in order to detect emergencies such as opiate overdose early.

Cheng added that in the future, he plans to look into implementing drug delivery through the gadget when it recognizes specific symptoms. “In the future, a device iteration may detect a drug overdose in real time and give naloxone, potentially saving a user’s life,” Cheng added.

A sensor for humid environments

Most wearable sensors employ superhydrophobic materials to repel water, but they are rigid and degrade quickly in humid situations, which is a serious concern in field hospitals and other medical institutions without climate control, according to Cheng. To overcome the challenge, Cheng’s team coupled superhydrophobic materials with Joule heating, a method of producing heat by passing an electric current via a conductor. Even when the sensor is in an environment with 99 percent humidity, the heat ensures continual moisture resistance.

As a result, a new flexible pressure sensor that can endure high humidity levels has been developed. The information was made public ahead of the March issue of Chemical Engineering Journal on the company’s website.

Cheng’s sensor is comprised of a transitional metal and sodium alginate, a food-grade substance derived from algae, which allows it to reject big water droplets, similar to how a lotus plant does in nature. “Water droplets on lotus leaves roll off easily, preventing water accumulation,” Cheng explained.

The sensor can monitor a user’s vital signs even under “severe use scenarios,” such as when they are sweating while jogging, riding, or sunbathing, because of its sturdy materials and continual heat, according to Cheng.

Cheng’s research team will continue to revolutionize the wearable medical devices sector despite all of his numerous discoveries and breakthroughs.

“We never know where inspiration will strike,” Cheng added. “Tissue paper, lotus plants, motion power, and other things have all proven to be fruitful sources.” “Our team is relishing the challenge of developing the next generation of medical devices, from discovery to research to implementation.”

Photo by Luke Chesser

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