Novel energy harvesting tech could reshape medical devices

Article By : Emily Newton

One primary downside of medical devices is that their batteries need replacement or recharging. That may not be the case for too much longer with this development.

Medical devices have come a tremendously long way over the years, saving lives and helping people manage illnesses. However, one primary downside is that their batteries need replacement or recharging. That may not be the case for too much longer as researchers make progress with devices capable of energy harvesting, bringing new options to developers and those who need the products.

Removing the Need for Pacemaker Battery Replacements

Millions of people rely on pacemakers and other implantable cardiac devices to keep their hearts functioning normally. However, those items need battery replacements every decade or sooner. Replacing the battery requires the patient to undergo surgery. Besides the expenses associated with those ongoing procedures, any operation carries the risk of complications.

Researchers at Dartmouth University hope to use the heart’s energy to power pacemakers. If that idea becomes a reality, it could eliminate those scheduled surgeries to replace batteries.

The team’s goal was to harness the kinetic energy of the pacemaker’s lead wire that gets attached to the heart. They used a polymer piezoelectric film called PVDF that turns mechanical motion into electricity if designed with porous structures. In 2019, researchers had progressed enough with development and testing that they believed the device was five years away from commercial availability.

Although it’s not on the market yet, this feature could be an attractive selling point for medical device makers and physicians who assess which products are best for their patients’ needs. This dime-sized invention fits inside existing pacemakers and is also scalable to offer future functionality such as real-time monitoring.

Developing More Devices That Are Safe to Use in the Body

One of the enduring challenges of designing an implantable medical device is finding a material durable enough to withstand the harsh and varied conditions inside the body without introducing toxic elements or other complications.

Piezoelectric options for energy harvesting offer a wide range of factors that determine the overall electricity output. Some are intrinsic, like the frequency constant of the piezoelectric element. Extrinsic factors, such as acceleration and amplitude of the movement, matter too. As you might imagine, materials selection is also critical when capitalizing on this effect.

Many materials used for piezoelectric projects are naturally occurring, such as enamel, bone and crystal. However, another obstacle in biocompatible materials selection is that they’re often too stiff to conform to the body’s surfaces. A medical device may need flexibility similar to a bandage, depending on its purpose.

Building Biocompatible, Piezoelectricity-Powered Wafers

Bioengineers recently developed “piezoelectric wafers” that could be used to generate electrical stimulation to speed fracture and wound healing and assist stroke patients by maintaining muscle tone.

In this case, lysine, an amino acid, is the piezoelectric generator. A shell made from a biocompatible polymer surrounds the lysine. The lysine and polymer’s chemical interaction positions the lysine into a crystal structure that creates an electrical current when bent. The researchers believe their creation could eventually let someone’s natural movement accelerate the healing process.

Another huge advantage of these devices is that they’re biodegradable. So far, the team has tested the wafers in rodents’ legs and chests. They then conducted lab experiments after the products naturally dissolved, which showed no evidence of harmful effects to the rodents.

If innovations like these become available to the public, medical device makers should strongly consider highlighting the biodegradability aspect. Some patients may understandably be wary of having devices put into their bodies if their physicians suggest it. However, if they know the gadgets will break down after use and feature nontoxic materials, they should feel more open to the idea.

Creating Low-Profile Wearable Medical Devices

The devices covered here so far go inside the body. Outwardly visible products require specific considerations to make them more likely to sell. Comfort is a primary necessity for encouraging user adoption and increasing their chances of going about their lives as usual.

That’s especially true when the goal is to capture details that may not be evident during medical appointments. For example, Finnish researchers designed a connected jumpsuit for babies that tracks their movements and monitors development. In that case, it was vital that the wearable didn’t annoy the infants or cause discomfort.

Feeling self-conscious is an issue for many adults. It’s vital to prioritize wearable medical devices that are easy to hide or otherwise won’t make someone feel embarrassed when using the product at college, work or another public place.

That’s why engineers developed an energy harvesting device people can wear under a baseball cap. It’s a hair follicle stimulation device that triggers regrowth from dormant structures. This approach uses nanogenerators that passively collect energy from a wearer’s normal movements before transmitting low-frequency electric pulses to the scalp.

Lab tests in hairless mice showed that the device worked as well as two compounds found in baldness medications. However, it doesn’t cause unpleasant side effects, such as depression and sexual dysfunction, that those products can.

Making Wearable Medical Trackers More Convenient

Health care providers increasingly use connected wearable medical devices to track everything from a patient’s heart rate to blood sugar levels. These products are ideally items that people can wear continuously without issues. In reality, most need periodic recharging, but a North Carolina State University team wants to overcome that barrier with a device that gets its energy from human body heat. This invention is a type of flexible thermoelectric generator (TEG). Most previous efforts to make bendable TEGs fell short of how rigid devices performed. However, the researchers made design tweaks with impressive results.

They originally made a proof of concept TEG in 2017. However, the engineers said an upgraded type announced in 2020 was closer to the efficiency provided by stiff devices. One of the components is EGaIn, a nontoxic alloy of gallium and indium. It provides stretchability plus electrical conductivity similar to metal.

Mehmet Ozturk, who worked on the project and coauthored a research paper about it, explained, “The key here is using a high thermal conductivity silicone elastomer doped with graphene flakes and EGaIn. The elastomer provides mechanical robustness against punctures while improving the device’s performance. Using this elastomer allowed us to boost the thermal conductivity — the rate of heat transfer — by six times, allowing improved lateral heat spreading.”

Energy Harvesting Opens Exciting Possibilities

Wearable and implantable medical devices are increasingly common, whether they treat an ailment, accelerate the healing process or help physicians track a patient’s status. These products are especially beneficial if users do not need to go through the hassle of recharging or replacing their batteries. The examples here show what’s possible and illustrate why energy harvesting could be essential for making medical gadgets more valuable and practical.

This article was originally published on Embedded.

Emily Newton is a technology and industrial journalist who enjoys discovering how the IoT is impacting different industries. Emily is editor in chief of Revolutionized – an online magazine exploring trends in science, technology and industry. Subscribe to her newsletter to keep up with the latest.


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