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Batteries for Wearables—Not Good Enough Yet

Many in the medical device industry are skeptical about the long-term reliability, safety, and quality of wearable medical devices and the batteries that power them.

Neil Oliver

The technological convergence of smartphones, smart watches, and fitness devices with pulse oximeters, electrocardiographs, glucose meters, ultrasound scanners, and kidney diagnostic systems is blurring the lines between consumer electronics and medical device technology. This convergence could have potentially great consequences for the development of both industries--especially in the area of batteries.

While wearable medical devices will continue to revolutionize our lives, many experts are raising eyebrows at what they believe to be a bad precedent: an incompatibility between two industries that operate in fundamentally different ways. The problem is one of business strategy. The last decade has witnessed unprecedented globalization, including cross-border trading blocs resulting in international supply chains with highly responsive logistical networks. This development has increased competition in the global marketplace and created a price-based race to the bottom.

As a result, consumer product development life cycles have shrunk drastically. For example, the typical consumer product life cycle is 12 months, although it can stretch to 24 months and be as short as six. This short lifecycle can be attributed to increased disposable income in emerging economies, more global competition, access to cheap labor, and incessant consumer demand for the next best thing.

In contrast, medical device product development life cycles are much longer--typically 10 years. Because of lower production volumes, higher R&D costs, more-lucrative healthcare contracts, and higher returns on investment, medical devices are designed to last much longer than consumer products. Consequently, many in the medical device industry are sceptical about the long-term reliability, safety, and quality of wearable medical devices and the batteries that power them. They are also concerned that as average life expectancy increases, it is vital to develop sustainable solutions for devices that are used to monitor and regulate human health.

Gaurav Jain, PhD, senior research manager at Medtronic Energy and Component Center, will be speaking on "Nex-Gen Power Sources for Medical Devices" at the MD&M Minneapolis Conference, September 21-22.

What Kinds of Batteries Do Wearable Devices Need?

The trend toward smaller batteries to accommodate smaller and lighter devices has led to several trade-offs. The most common battery used in medical device applications is the lithium-ion (Li-ion) cell, but such batteries have limited gravimetric and volumetric energy density, inevitably resulting in inadequate runtime. The lifespan of a rechargeable consumer Li-ion battery averages approximately 300 to 500 charge cycles before its capacity drops to an unacceptable level. Thus, because medical devices outlive their batteries, they tend to use removable rather than embedded technologies.

While it may be inconvenient for a smartphone to run out of juice, it can be downright catastrophic if the battery in patient's health monitor dies. To combat this problem, credit-card-sized batteries have been developed for use in wearable medical devices that monitor patients' health or dispense medication when required. And because they are removable, such batteries can be swapped for another when charging is required without having to return the device to the manufacturer for a replacement.

Schematic drawings show the Li-ion polymer cells, injection-molded casings, a fuel-gauging PCB, and other elements of a battery.

Although battery quality is a major problem for consumer medical devices, the manufacture, testing, and regulation of the battery industry pose even greater concerns for medical device manufacturers. Because the industry has seen rapid growth over the last three years, many battery manufacturers in the Far East have taken shortcuts by producing grey-market knockoffs and sometimes outright illegal Li-ion batteries. Such batteries lack the necessary protection circuits that are needed to prevent them from overcharging, overheating, or becoming unstable, which can potentially result in a fire hazard.

In response, many OEMs have taken action to protect their intellectual property rights against fake or copycat batteries by introducing such security features as invisible inks and holograms. For its part, Accutronics has incorporated an advanced software-security algorithm into its batteries, ensuring that a medical device uses only an authorized battery. When a medical device manufacturer incorporates this algorithm into its device, the device detects and rejects a fake battery, causing it to take appropriate action, as defined by the vendor. Such action can include failing to power up or notifying the user. However, taking such measures is only a reactive response.

Need for Regulatory Intervention

To a considerable extent, wearable medical devices have so far failed to advance beyond the reactive stage because the very definition of a medical device is becoming blurred. Although the medical device industry is one of the most regulated in the world, it has struggled to keep pace with the advent of wearables.

Should smartphones that are used to relay information from wearable devices for measuring, diagnosing, and recommending treatment be regulated as IT equipment under the IEC 60950-1 standard, or should they be regulated as medical devices under the IEC60601-1 standard? In many countries, manufacturers must meet these standards to commercialize electrical medical equipment.

This ongoing ambiguity led Apple to consult with FDA on the use of sensors in its devices, which may ultimately lead to regulatory review. Although information-only apps are currently exempt from FDA regulation, measurement apps such as glucometers are considered diagnostic in nature. This conversation led Apple to release the Healthkit software development kit.

In Europe, the European parliament has issued directives on the classification of medical and in vitro medical devices that include a broader range of products than those regulated by FDA. Included in these directives are noncorrective contact lenses, aesthetic implants, and device software. These regulations are also more selective in awarding CE marks to high-risk devices, which must undergo further clinical trials to assess their risk.

Meanwhile, the UK's Medicines and Healthcare Products Regulatory Agency has published guidelines stating, "the manufacturer of a device is responsible for establishing that the device is safe and that it is suitable for its intended purpose. To establish this, manufacturers implement appropriate controls on the device design and manufacture, and evaluate the safety and performance of the device in its intended application."

Wearables May Be Here to Stay, But...

The average smartphone now has more processing power than the supercomputers used by NASA in 1969, when it sent three astronauts to the moon. Thus, it is not surprising that startups have flourished in recent years that are devoted to developing peripheral devices for monitoring the intimate details of patient's physical condition. This trend was highlighted at the 2015 Consumer Electronics Show, which provided OEMs with an opportunity to exhibit their latest and greatest inventions--from smartwatches that can track your heart rate and sleep quality to armchairs that exercise you in the comfort of your own home. A hearing aid developed by Siemens even allows users to zoom into sounds.

The rise of wearable devices has been attributed to a much larger societal disposition toward the Internet of Things. Although the concept of the Internet of Things has been around for many years, only recently has it started to gain traction. A maturing ecosystem of mobile operating systems such as Android and iOS, as well as an improving cloud computing infrastructure and the widespread availability of cheap wireless sensors, means that OEMs in the consumer electronics sector have glimpsed the prospects of earning profits in the medical technology sector, and they want a piece of the pie.

The ability to create cheap devices that do not require heavy on-board processing but outsource this function to a server in the sky means that nearly every household object can be equipped with a sensor and a screen. As a result, patients now receive up-to-date information on many ailments and long-term conditions. For example, diabetics can use peripheral plug-in gadgets to monitor blood glucose; chronic kidney patients can avoid time-consuming visits to the doctor by testing themselves at home; and patients with a gruelling pill regime can track their exact intake using a handy smartphone app.

Thus, the benefits of wearable and portable medical devices are clear. Wearables make data readily accessible and may reduce the frequency with which patients visit the doctor. As a result, they may alleviate the burden on the healthcare system. Moreover, it is becoming cheaper to produce wearable medical devices that fulfil the functions traditionally carried out by large and expensive medical devices available in hospitals. But for wearable medical devices to fulfil this mission, new enabling technologies--including batteries--must be developed and marketed.

It is clear that the world of wearable medical devices is not at all what it seems at first glance. Upon closer examination, it is evident that numerous economic, cultural, and regulatory changes are needed before wearable medical devices can be sustainably and safely integrated into our everyday lives. With the right power management, design, and production controls and when used under the guidance of healthcare professionals, wearable devices can become a viable asset for improving the health of our increasingly aging population.

Neil Oliver is technical marketing manager at Accutronics Ltd., based in Newcastle-under-Lyme, UK. With more than two decades of experience in battery manufacturing, Oliver works with global OEMs to develop customized rechargeable battery solutions for portable electronic products. He also coordinates the company's technical marketing efforts and frequently authors technical articles in trade publications and on the company's blog. Reach him at neil.oliver@accutronics.co.uk.

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