Solar Powered Wearables Will Soon be Feasible with Newly Developed Ultrathin Organic Photovoltaics

Solar power's revolutionary capabilities have already been proven beyond doubt. With its burgeoning success, coupled with technological innovations enriching it every day and the rising demand for renewable energy, the global smart solar power market could surpass US$27 billion by 2028 from under US$13 billion in 2022.

The growth projections indicate a doubling of the market, witnessing high-end innovations in photovoltaic materials, energy storage, smart grids, solar energy systems, and much more. Notably, Solar energy is also leaving its mark in the field of wearables, with research and experiments soon expected to introduce solar-powered wearables. 

Ultra-flexible Organic Photovoltaics as a Potential Power Source for Wearable Electronics

New research published on Nature Communications, titled ‘Waterproof and Ultraflexible Organic Photovoltaics with Improved Interface Adhesion,' highlights the ultraflexible organic photovoltaics' stretchability and lightweight nature, making them a potent power source for electronic wearables. The research, however, acknowledges that waterproofing these solutions remains a challenge if their mechanical flexibility and conformability are kept unaltered. 

It has shown how this challenge can be addressed, essentially positioning organic photovoltaics as a superior solution. The solution involves leveraging the in-situ growth of a hole-transporting layer to strengthen interface adhesion between the activity layer and anode. To be more specific, the solution allows a silver electrode to deposit on top of the activity layers. The deposition is followed by thermal annealing. 

The research finds that the in-situ method far surpasses the conventional one by showing that the in-situ grown hole-transporting layer possesses superior thermodynamic adhesion properties between the active layers, leading to improved waterproofing properties. 

In the experiment, three-micrometer-thick organic photovoltaics fabricated through this method retained 89% and 96% of their pristine performance even after being immersed in water for four hours and undergoing 300 stretching/releasing cycles at 30% strain underwater, respectively. 

While these numbers stood testimony to their flexibility and waterproofing features, the devices seamlessly underwent a machine-washing test despite their thin encapsulation layer. 

Overall, the experiment could show how solar cells could become waterproof and conducive to large-scale operations. 

The solar cells could now be functionally integrated into clothes, remaining effective even after being exposed to rain or being subjected to a wash cycle. This innovation is, therefore, particularly significant because it could be valuable in creating wearable electronic devices that can be attached to clothes and remain workable in all sorts of weather conditions. 

While speaking about the experiment and elaborating on its potential utility, Kenjiro Fukuda, one of the corresponding authors of the paper, had the following to say:

“What we have created is a method that can be used more generally. Looking to the future, by improving the stability of devices in other areas, such as exposure to air, strong light, and mechanical stress, we plan to further develop our ultrathin organic solar cells so that they can be used for really practical wearable devices.”

While researchers worldwide are keen to make solar cells more usable and practically significant, some businesses are investing heavily in R&D to develop scalable solutions that benefit a larger population. 

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#1. Garmin

Garmin has developed a whole line of solar-powered smart wearables that claim to extend battery life to unprecedented levels. The lineup includes three smartwatches: Fenix 7 PRO, Instinct 2, and Forerunner 955 Solar. It has devised the products, especially for outdoor use. 

These smartwatches can harness solar energy even when the watch's face is partially obscured. Their power manager feature allows the user to tailor and customize energy use according to needs.  

To give specific data, the watch can handle outdoor expeditions for up to two months without requiring any additional power source. Moreover, the solution is green as it produces 59 percent less carbon emissions than other watches. 

The Fenix 7 Pro, for instance, leverages ultra-transparent solar panels. Its sleek design can optimize sunlight absorption. Instinct 2 is a solar-powered GPS smartwatch. The Forerunner 955 is designed specifically for running. 

Garmin has achieved many technological marvels in building its solutions. For instance, its power glass system has radically altered how solar panel technology is used. It has replaced conventional solar panels with a super-transparent glass lens integrating microscopic solar conducting cells. The glass panel is ultra-thin, less than half a millimeter. 

In a display of technological prowess, the panel is not only capable of effectively capturing photoelectricity but also incorporates Memory-in-piece display technology to create a clear and legible screen. High clarity and low power usage, even under direct sunlight, make it best-in-class. 

On February 21st, 2024, Garmin® Ltd. announced its results for the fourth quarter ended December 30th, 2023. The company earned a consolidated revenue of $5.23 billion, an 8% increase compared to the prior year. 

It registered a gross margin of 57.5%, compared to 57.7% in the prior year, and an operating margin of 20.9%, compared to 21.1% in the prior year. Operating income was $1.09 billion, a 6% increase compared to the previous year.

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#2. Tommy Hilfiger

For Tommy Hilfiger, the globally-revered fashion and clothing brand, solar-powered wearables are not new, having introduced a solar-paneled field jacket line almost a decade earlier, in 2014. The job was accomplished with the help of Pvillion, a solar manufacturer. The jacket came with waterproof solar panels that worked as back-coat linings. These panels were designed to charge devices via built-in cables and USB ports. 

At the time of its launch, the jacket was selling for US$600. The jacket designed by Tommy Hilfiger, in collaboration with ‘Pvilion', served as an inspiration. Seven years after the launch, in 2021, Finland's Aalto University's design and physics researchers came up with a clothing brand that had concealed solar panels. 

The project, known as Sun-Powered Textiles, led to the development of an energy-autonomous product that could charge wearable devices – sensors that measure humidity or temperature – without disrupting the look and feel of the garment.

While elaborating on the uniqueness of their innovation, Aalto University design researcher Elina Ilen had the following to say:

“We made a demonstration case, a jacket, where the light energy is used for powering integrated humidity and temperature sensors, thinking of the workwear user, who goes in and out and does physical tasks daily.” 

These innovations, both by Tommy Hilfiger and Aalto University, are examples of how our clothes could have solar panels in a disguising and easy-to-use way. 

PVH Corp., the entity that owns the Tommy Hilfiger brand, reported its 2023 fourth quarter and full-year revenue on April 1st, 2024. Full-year revenue increased 2% to $9.218 billion compared to the prior year period, while fourth quarter 2023 revenue of $2.490 billion was flat as compared to the prior year period. 

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#3. Skagen (Owned by Fossils Group)

In August 2022, the well-known watch and jewelry brand Skagen came out with its sustainable collection, Grenen Solar. Its design included a 3-hand Japanese solar-powered movement for precise timing. It also promised a six-month power reserve. Owing to its solar-powered movement, the person wearing it could charge the watch in any light, natural or artificial. 

One of the specialties of Grenen Solar was its commitment to keeping sustainability at the center of its innovation expertise. And sustainability was not only in the form of using solar power. The release of the product was, in fact, in line with the vision and commitment of the company to have its watches to be 100% sustainable in the near future. To this end, 50% of the steel used in the watch was recycled stainless steel. Additionally, the overall collection came with five styles in a 37 mm case size at a retail price of US$195. 

In January 2012, Skagen was sold to the Fossil Group in a US$237 million transaction. On March 13th, 2024, the Fossil Group published its annual report for the Fiscal Year 2023. In 2023, the company registered net sales of more than US$1.4 billion, a decline from 2022, when it recorded net sales of US$1.68 billion.

Overall, the above products and solutions make it amply clear that solar-powered wearables are nothing new. However, as we had shown in the beginning, the innovation around it is robustly ongoing. It shows the vitality and worth of renewable energy sources and their sustainability potential. Several other interesting innovations are ongoing, and we will look into a couple of them to get an idea of what the future looks like.

Solar-Powered Wearables: What the Future Holds

In 2017, researchers presented the design of a wearable smart bracelet that used thin-film, small-form-factor flexible photovoltaic panels as an energy source, marking a significant advancement in solar energy harvesting subsystems. It aimed to maximize energy conversion efficiency and achieve a self-sustainable wireless wearable system. 

By leveraging polyamide film for full-system integration, the technology proved beneficial in the long-term monitoring of patients or elderly people in healthcare applications. The results were promising, as a single flexible solar panel could harvest up to 16 megawatts of power outdoors and 0.21 megawatts indoors. Impressively, the data gathered by the device could be transferred via Bluetooth. 

Continuing research in healthcare resulted in the development of a battery-free, solar-powered wearable biosensor that could tap into the underutilized potential of sweat biomarkers. The research output was the LumiStat, a solar-powered, multifunctional wearable capable of performing autonomous sweat induction, dynamic microfluidic sweat sampling, multiplexed monitoring of sweat biomarkers, and wireless data transmission, a breakthrough in non-invasive health monitoring technology. 

Being solar-powered made it capable of remarkable performance, enabling continuous operation for more than 12 hours under diverse light conditions. The researchers put LumiStat through rigorous testing, including a day-long, cross-activity multimodal monitoring of sweat biomarkers. The solution could perform consistently across diverse lighting environments and physical activities, with power consumption intelligently adapted to the available illumination, ensuring continuous sensor measurements.

A research report published by Nottingham Trent University discussed the development of textiles embedded with more than a thousand miniature solar cells. These solar cells were capable of charging smartwatches and mobile phones. Combined, they could harness 400 milliwatts (watts) of electrical energy from the sun. 

The textile was suitable for everyday clothing and could be washed in a machine at 40°C with other laundry. Measuring only five millimeters in length and 1.5 millimeters in width, the solar cells were embedded in a waterproof polymer resin. Even the weaver could not feel them. 

According to Dr Hughes-Riley of the university's Advanced Textiles Research Group (ATRG):

“This prototype gives an exciting glimpse of the future potential for e-textiles. Until now, very few people have considered that their clothing or textile products could be used to generate electricity. The material we have developed appears and behaves the same as any ordinary textile, as it can be scrunched up and washed in a machine.” 

The material, measuring 51cm by 27cm, was both breathable and chemically stable. It featured silicon solar cells. This configuration enabled the material to generate a power output of 335.3 watts in 0.86 sunlight, with the capability to generate up to 394 watts when the sunlight intensity reached 1.0.

Evidently, with each passing day, more research is becoming available to the public that shows the potential of solar-powered wearable technology. It is game-changing, to say the least, and paradigm-altering. Since the solutions are meant to stay attached to our bodies at all times, changing the way we interact with technology. They remove the need for power intermediaries such as charge points. They increase our mobility and ability to explore more while worrying less about how to keep our systems running.