When it comes to wearables, nightly charging might not be convenient and in some cases, it might not even be possible. Here’s a round-up of the latest science on how to harvest ambient energy to continuously power our gadgets.
Neil Harbisson is pretty easy for most people to spot. He’s got a 12-inch metal antenna that curves over the top of his head. It was implanted in 2004, by an anonymous surgeon who feared the unsanctioned procedure might cause an uproar, and it allows Harbisson, who suffers from a rare form of color-blindness that restricts his view of the world to a series of grays, to detect color.
Last year, Harbisson added Bluetooth to the device, giving him the ability to upload images from his mobile phone, which can be sent by people from anywhere in the world. But it requires work on Harbisson’s part. In essence, his vision bypasses optic restrictions by giving him access to what a camera sees; he in turn “hears” the color frequencies sent to his brain, and distinguishes color by memorizing those frequencies.
Harbisson, famous for being the first person officially recognized as a cyborg when the British Passport Office accepted the image of him with his antennae, is an extreme case. But he’s also a sign of what could come as humans begin to incorporate wearable devices into our daily lives to enhance the way we experience and interpret the world around us.
Without question, wearable electronics are the wave of the future in gadgetry, and the reason is simple: Wearing our electronics is a major convenience and in some cases — typically of the medical variety — it is an imperative. It’s easier to stick, strap, or tattoo something on — and in some cases necessary to implant it — than haul it around in close proximity to our bodies, where it becomes susceptible to being dropped in toilets, sat on, or forgotten altogether while we juggle our to-go mugs and other non-attachable items.
Wearables are already in abundance, and go well beyond the better-known Google Glass, Fitbit and the rumored iWatch. Think straps, adhesives, tattoos, pendants, clips, pacemakers, electrode patches, and smart apparel, including in-soles and under-garments. If you can think of a way to wear a device, someone else has probably thought of it, too.
The limiting factor is not, it turns out, how the gadgets can be worn or what they can do, but how they are powered. As devices continue to miniaturize, and even economize their power needs, batteries lag. Even at their smallest they’re still big, bulky, and have limited life spans. While most of us just shrug and deal with the nightly charging of our devices, people who need to wear their devices aren’t just inconvenienced, they can suffer (think repeat surgeries to replace pacemaker batteries, which often run their course in seven years).
Scientists are already making headway on the power consumption side of the equation. In fact, one chip is in the works that could make all these wearable devices consume significantly less energy. And as energy efficiency improves, even low levels of ambient energy may be able to continuously power these devices, possibly doing away with batteries altogether.
Energy harvesting: Still outside the norm
The bulk of ambient power sources fall into five categories: photovoltaic (from light), thermovoltaic (heat), piezoelectric (mechanical stress), electrodynamic (vibration/movement) and biological (organic chemical conversion, i.e. from fat or sweat). Dozens of studies have come out in the past two or three years showing progress across all categories, but aside from a few outliers (i.e. the battery-less “biometric headphones” coming out of an SMS Audio and Intel partnership), the majority of energy harvesting remains confined to science labs and sketchpads.
Tom Emrich, an expert on wearables and cofounder of Wearable App Review, said that while patients in a medical setting are likely to be more open to harvesting energy from ambient sources like their own bodies because the doctor prescribed it and their health is at stake, it will likely take a few years for consumers to warm to alternative power sources when recharging batteries currently works for our first-gen wearables.
“As wearables become more the clothing and accessories we wear, I think energy harvesting will be huge and will be a major value proposition for why we wear our devices,” he told me. “But just the idea of wearables outside of medicine…people are just trying to wrap their heads around throwing in a new way to charge. At first we have to keep some of our norms, like throwing it on a cradle or plugging it in. So I think it’s coming, it’s inevitable and I’m really excited about it, but I wonder if it’s a couple years out.”
Body heat, human sweat, trapped light
Regardless of consumer comfort, it’s only a matter of time before further tinkering makes some of these approaches not only viable but also preferable to batteries. Here’s a roundup of some of the more promising and interesting power sources being studied today:
- Converting body heat into electricity using glass fabric
- Trapping light using organic photovoltaic cells woven into fabric
- Using energy generated by our own organs, including hearts and lungs
- Converting lactate from human sweat using epidermal tattoo biofuel cells
- Using electromagnetic radio waves to wirelessly power self-propelled injectables or implants that deliver drugs and perform biometric analyses
In the next few years, we’ll likely see the first iterations of applications like photovoltaic textiles, where we can wear clothing that converts solar or kinetic energy to power a simple system that monitors, say, calories burned on a jog. But Yogesh Ramadass, who has been working on ambient energy harvesting since he was a student at MIT and now as a lead design engineer at Texas Instruments, told me it’s important to separate out non-critical applications like monitoring one’s heart rate and body temp from life critical ones, like Pacemakers.
Given the implications involved if the ambient energy fails in something like a Pacemaker, he said, it could be many years before we are confident enough to rely on ambient energy to power the more critical medical devices without back-up batteries. In the meantime, a hybrid system — part harvesting, part back-up battery — will probably be the bridge, much in the way EV hybrids like the Chevy Volt help people conquer their fears of range anxiety.
“Those systems are possible, where 90 percent of the time you are harvesting, but 10 percent of the time to offer peace of mind or get through regulatory hurdles you’d still put in a small battery to back it up,” Ramadass said. “At the end of the day, [EV hybrids vehicles are] the same thing, just on a different scale. Because you don’t want to be in the middle of the road when your car stops.”
Photo credit: Studio Beat