Could Internal Batteries Power Next-Gen Wearables and Even Battle Cancer?

Wearable technology has been reshaping our daily lives for some time now, and it will only grow from here, as evidenced by the wearable devices market, which was valued at $61.30 billion in 2022. In that year alone, more than 490 million wearable units were shipped to consumers. 

Driven by innovation, wearables have been shaping trends that span industries from environmental sustainability to healthcare, where such electronics have transformed health monitoring, therapies, disease diagnostics, and wound healing. To operate reliably, these devices rely on batteries that are not only bio-compatible but also have sufficient capacity.

A majority of implantable devices are powered by traditional batteries like Ag-Zn (Silver-Zinc) and Li-I2 (Lithium Iodine) batteries. These conventional batteries, however, have limited capacity and pose a safety hazard from organic electrolyte leakage.  

Sealed and utilized for powering implantable devices, the capacity of Ag-Zn and Li-I2 batteries is restricted by their mass, which limits their service life. This is where a new study proposes utilizing components that living organisms contain naturally. These components include sweat, enzymes, glucose, and dissolved oxygen, which can be utilized as continuous energy sources for batteries.

Using active components like O2 and glucose as cathodes/anodes that can be obtained continuously through metabolism exhibits good electrochemical performance both in vitro and in vivo. 

Published in Cell Press, the study proposes metal-O2 batteries, which will use O2 as an active component in the cathode and be assembled with a metallic anode. This way, they will provide extremely high energy densities that are 5 to 10 times greater than the currently available implantable batteries. 

Theoretically, Li-O2 and Sodium–oxygen (Na-O2) batteries offer different energy densities of 3,458 and 1,605 Wh/kg, respectively. These figures far exceed those of current lithium-ion batteries.

The study was conducted by Yang Lv, Xizheng Liu, Jiucong Liu, and Yi Ding, all of whom are affiliated with the Laboratory of Advanced Functional Porous Materials, Institute for New Energy Materials & Low-Carbon Technologies, School of Materials Science and Engineering, Tianjin University of Technology, China. 

Other researchers included Shuang Wu and Pingli Wu from the College of Chemistry and Materials Science, Institute of Life Science and Green Development, Hebei University, China; Shuangyong Sun from the School of Pharmacy, Tianjin Medical University; and Yonggang Wang from the Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Institute of New Energy, iChEM, Fudan University, China.

The study received financial support from the National Natural Science Foundation of China, the National Key Research and Development Program of China, and the National Science Fund for Distinguished Young Scholars.

Implantable and Biocompatible Na-O2 Battery

Oxygen is essential to life and ubiquitous in living tissues. Similarly, Sodium, another essential element, is widely present in our bodies in the form of Na+. This ubiquity makes metal-O2 batteries a promising prospect for constantly replenishing power sources. 

While Sodium has been developed as a promising anode for rechargeable batteries, Na-O2 batteries have been particularly popular due to their low cost, high theoretical energy densities, and potential for usage in smart grids and portable electronics. Moreover, the discharge product of Na-O2 batteries can be easily metabolized in the liver and kidneys, adding to their appeal.

This way, Na-O2 batteries can meet the requirements of continuous raw material source supply as well as in vivo product metabolism.

As such, this isn't the first time that researchers have focused on Na-O2 batteries. In 2018, a study noted their potential thanks to their high theoretical energy density and abundant resources while calling attention to their sluggish kinetics due to the formation of large-size discharge products with cubic or irregular particle shapes. 

Another paper by Hossein Yadegari and Xueliang Sun from the Department of Mechanical and Materials Engineering at the University of Western Ontario noted that Na-O2 batteries have emerged as an energy-efficient alternative to Li-O2 batteries. They rely on reversible superoxide chemistry, with their cells showing lower overpotential charging in comparison to their Li counterparts, which can be translated into high cycling performance. 

However, it pointed out that the interaction between the ion pair is insufficient to prevent the nucleophilic attack of O2 against the cell electrolyte. Additionally, the intrinsic stability of NaO2 and the higher chemical reactivity of metallic Na present challenges in the progress of Na-O2 batteries. Although there have been relatively few reports on these batteries, the significant potential advantages of implantable metal-O2 batteries underscore the importance of addressing the existing challenges.

The latest study highlights the necessity for batteries utilized in vivo to have an open architecture, ensuring the adsorption of O2 from the body fluids. Furthermore, it emphasizes the importance of selecting battery components that exhibit good bio-compatibility to avoid rejection and reactions. On top of that, due to being highly reactive, the Na-based anode must be well protected. Battery design further needs to be flexible to allow for stable and intimate contact with soft tissues.

As a result, the team proposes a novel Na-O2 battery design that utilizes a stable Na-based alloy (NaGaSn) as the anode (from where electricity moves into) and nanoporous gold (NPG) cathode (where electricity flows out) component that was separated by an ion-exchange membrane (Nafion).

Instead of using a pure metallic Na, the researchers opted for a NaGaSn ternary alloy to enhance safety and anti-corrosion properties in living organisms. Meanwhile, the NPG was used as a cathode in metal-air batteries for the oxygen reduction reaction. During discharge, the O2 is supplied continuously from body fluids and reduced via NPG catalysis. 

Promising Results, Potential Applications 

As implantable electronics gain increasing traction due to their potential to revolutionize personalized healthcare monitoring and precision therapy, the importance of implantable batteries grows correspondingly. Here, the use of active components from living organisms can provide long-term power sources, thereby reducing the need to replace batteries repeatedly through surgical processes, offering a more sustainable long-term solution. 

The study successfully developed an implantable and biocompatible Na-O2 battery featuring an open cathode structure that operates smoothly. In rats, the laminated battery achieved a power density of 2.6 μW/cm2 at 1.3 V, demonstrating excellent biocompatibility in vivo. 

The results showed no significant inflammation around the implanted batteries. Moreover, capillaries regenerate well around the cathode, providing a continuous source of O2 for the battery. 

Meanwhile, the NPG cathode catalyst enabled the battery to achieve excellent stability, which, the study said, makes NPG the “inevitable choice” as the cathode of the Na-O2 battery. The electrospinning PLCL membrane helped improve biocompatibility, and the membrane's porous structure, which served as channels for the transportation of mass and electrolyte, allowed the permeation of body fluid and diffusion of O2. 

As for the Na+ and OH− ions produced during the discharge process, they entered the blood without causing electrolyte disturbance, and their metabolism in the body did not result in any abnormalities in the liver and kidneys. 

The study results also showed promising potential as an energy source for powering micro-implantable electronics. Furthermore, consuming O2 from body fluids highlights the Na-O2 battery's potential applications in biological and medical investigation fields. According to the study:

“Our Na-O2 battery revolutionizes the concept of implantable batteries, the consumption of O2 during discharging results in a deoxygenation function, which also offers a new way to combine bio-electronic implants and biotherapy toward the diseases associated with anaerobic environments.” 

So, the Na-O2 battery clearly has some great potential, but it isn't limited to just powering the wearables; rather, it can see much greater usage, including cancer applications and monitoring wound healing.

The study further noted that senile dementia and cancer are closely related to oxygen levels in the relevant tissues. A recently reported self-charging saltwater battery for antitumor therapy by consuming O2 opens a new way to combine bioelectronic implants and biotherapy.

Controlling the O2 concentration in the present battery precisely demonstrates potential therapeutic capabilities against diseases caused by oxygen aggregation or pathogenic bacteria. Moreover, the catalysts in the cathode of Na-O2 batteries can reduce the superoxide radicals that cause senile dementia, highlighting its potential applications in these fields as well. 

So, while many challenges still need to be addressed, the Na-O2 (Sodium-Oxygen) battery is “highly promising and can spark a new revolution in the field of implantable devices, leading to the development of new methods for the treatment of various diseases” the study stated.

Click here to learn about the next-gen creative wearables – Thermal Earrings

Biotech Wearable Solutions in Development  

Wearable technology is primarily about electronic devices worn on the body to monitor metrics. Today, these devices are advancing a wide range of industries, from medicine, sports, and fintech to manufacturing and more.

In the sports industry, wearable devices provide athletes with real-time data and feedback on their performance. Smart sunglasses, footwear, and clothing use sensors to track and monitor heart rate, steps, and physical activity, among various other metrics. This information can then be used to make improvements in particular areas and adjust fitness and training plans accordingly. 

In the manufacturing sector, these devices help ensure workplace safety by providing real-time alerts and information on potentially dangerous situations. Meanwhile, by tracking worker efficiency and productivity, they help identify areas for improvement and then make appropriate adjustments in workflows.

It is, however, in the healthcare industry that wearable technology via devices like smartwatches, fitness trackers, biosensors, blood pressure monitors, and electrocardiogram (ECG) monitors is really shaking up things. 

Wearables allow users to collect their own health data and, based on that, take action. Healthcare professionals can mitigate life-threatening situations through real-time patient monitoring, which is made easy with wearables. 

These devices track and monitor vital signs and health data, enabling doctors and caregivers to find potential health issues and then provide timely interventions. They also provide researchers and doctors with valuable insights to advance clinical research and develop new therapies and treatments.

Meanwhile, providers and insurers can utilize these devices to offer more accurate and personalized health plans. Organizations are also making use of them to encourage healthy habits among employees.

In the biotech sector, wearables allow for noninvasive physiological status monitoring as well as state of disease and toxin exposures. They can be a great help in precision medicine by allowing researchers and scientists to identify any potential side effects. Moreover, wearables offer insights into environmental conditions, such as temperature and air quality, to study their effects on biological systems. 

Now, let's take a look at some companies developing wearable solutions. 

#1. Google-Acquired Fitbit 

This one is a pretty well-known name in the wearable industry for its fitness trackers that monitor various health metrics such as activity levels, heart rate, and sleep patterns. It further offers a coaching platform that provides solutions for researchers, healthcare systems, and corporate wellness. Fitbit is mainly focused on consumer fitness and has been partnering with healthcare companies.

Earlier this year, Google's Fitbit partnered with lab test company Quest Diagnostics to study how wearable technologies can improve metabolic health and possibly prevent diseases such as stroke, diabetes, and dementia, among others. Another was with ViviHealth for predictive and prescriptive analytics to transform behavioral health centers.

Google is a $1.9 trillion market cap company with its share at $153.16, up 9.5% YTD. The company's Revenue (TTM) has been $307.39 bln, EPS (TTM) of 5.80, and P/E (TTM) of 26.41.

#2. Garmin 

The company produces wearable devices for fitness activities with features for monitoring heart rate, stress levels, and even pulse oximetry. Its Venu series tracks body patterns and sleep quality and pairs with Android and Apple smartphones for added convenience. Through its devices, Garmin helps users maintain health goals and aims to improve overall societal health, promote wellness, and reduce healthcare consumption.

The company started three decades ago with its cutting-edge GPS navigation products for the aviation industry, only to expand to cover the marine, automotive, outdoor, and fitness markets. Its current focus is on expanding in the Indian market and capturing its increasing ‘middle-class' consumer base.

#3. Abbott Laboratories

The company develops various medical devices, including wearable technologies. This includes FreeStyle Libre, a small circular sensor attached to the upper arm that provides real-time glucose readings for people with diabetes to help them manage their condition more effectively. The market-leading wearable glucose sensor has over 5 million users around the world.

Besides diabetes, the Illinois-based company also provides services in physical movement and cardiology. With a market cap of $193.62 bln, the shares of the company are trading at $111.56, up 1.53% YTD. The company's Revenue (TTM) has been $40.10 bln, EPS (TTM) of 3.27, and P/E (TTM) of 34.10.

#4. BioTelemetry Inc. 

Now part of Philips, BioTelemetry provides remote medical monitoring systems, including wearable devices for cardiac monitoring. These wearable sensors track heart rhythm abnormalities and other cardiac metrics in real time. Late in 2020, Philips acquired BioTelemetry in a $2.8 billion deal.

Conclusion

The wearable technologies market is booming and is projected to surpass $118 bln by 2026. After all, wearables are entering into a wide range of industries, from fitness, education, and entertainment to travel and fashion. 

However, with health concerns rising, wearables are particularly creating a meaningful impact on our habits, health, and lives. Although these devices are getting increasingly sophisticated, the battery problem is something that must be solved. 

As we can see here, studies are being conducted to prolong the lives of wearables and help them battle diseases like cancer. In the future, tech advances and research will help wearables get even better at providing personalized care and significantly improving patient outcomes.

Click here for a list of top wearable health-tracking companies to invest in.