Wireless charging capabilities are being built in to almost everything … but is wireless electricity safe for everyone? That depends. Not all wireless power is created with the same technology.
Chances are, you own a device that has an inductive charging feature built in. If you’re able to charge your earbuds, toothbrush, mobile phone, tablet, or any other small device by setting it on or near a charging pad, you have an inductive coils — also called Qi — device.
According to Bank of America Global Research, by 2025, there will be 10 connected devices per person that need charging. That’s a lot. Obviously far to many to conveniently charge with wall dongles and cords!
Now consider whether you or someone you live with has an implanted medical device, like an implanted defibrillator or pacemaker. If you do, take extra precautions, because inductive charging devices use low frequency electromagnetic waves, and some also use strong attachment magnets, that have the potential to interfere with the electronics in those implanted medical devices. Apple has recently listed a series of their products that should stay at least 6 inches away — and more than 12 inches away while charging — from anyone’s implanted medical devices.
That’s a tough ask and something that requires vigilant aware. As the name implies, by nature, many ‘personal devices’ are carried close to or on your body: watches on your wrist, headphones on your head, tablets and phones resting on your stomach or chest while in use, and phones charging nearby or on your nightstand for easy access.
Is wireless charging problematic from this perspective? Not so fast. There are multiple flavors of wireless power available.
Radio frequency (radio waves) vs inductive charging (magnetic fields)
Not all wireless electricity is transferred employing the same kind of technology. For example, radio frequency (RF) or microwave is a wireless power at a distance technology that is being rapidly adopted for commercial use and doesn’t employ Qi charging, magnets, or magnetic resonance at all. It’s just a matter of time before we see RF-based wireless power automatically built into consumer electronics.
Unlike low frequency waves and magnetic fields, microwave radio waves do not penetrate deeply into human tissue, so there is far less concern with interference to implanted medical devices. Let’s compare the differences between the technologies.
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Microwave radio-wave-based wireless electricity (like Cota) |
Qi inductive coil charging with attachment magnets and magnetic resonance (like Apple’s link above) |
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Body absorption |
Waves remain confined at the surface (an effect that is called skin depth or skin effect); little deep body penetration |
Low frequencies and magnetic fields can penetrate deeply into the human body |
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Charging pad |
No charging pad, coils, or magnets required. Little likelihood for interference to implanted medical devices. |
Some technologies (like Apple’s MagSafe) use rings of strong magnets on the charger and device to adhere them together for coil charging, which can potentially interfere with implanted medical devices. |
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Frequency range |
Cota 5.8 GHz uses Giga (billion) Hz frequency range (41,000 times higher than Qi and 855 times higher than magnetic resonance frequencies). The typical penetration depth for 5.8 GHz is less than a few tenths of an inch. |
Qi and MagSafe use ‘kilo (thousand) Hz frequency range’ and resonance uses ‘Mega (million) Hz frequency range’. MagSafe magnets, Qi, and magnetic resonance use fields that can penetrate deeply into the human body. |
Medical devices are not the only products potentially affected by Qi, magnets, and magnetic resonance
With a world being dominated by IoT, wireless electricity (or delivering wireless power automatically without the need for wires or batteries) is becoming more and more of a must. But Qi is limited in its ability to fulfil the need for a truly automatically charged world, because of its requirement for contact (or near contact) with the charging pad.
For one, proximity to a Qi charging pad or surface is required, so it’s not truly wireless. There are also the placement constraints that often require precise alignment to effectively charge. Also, we’re learning that there are many situations where Qi is not well suited, because of potential interference issues. In addition to medical devices, these include other categories of devices that can be sensitive to low frequency waves or magnetic fields.
In 2021, the market size of wireless electricity is estimated at $5.71 billion. By 2030, it’s projected to reach $35.21 billion (by BofA Global Research). In less than 10 years, we, as a community of alternative energy innovators, need to set the direction for safe, flexible wireless power over-the-air to fuel the growth of IoT, 5G and Edge Computing.
Ten years seems like a short time to achieve such a major shift, but we’ve known about wireless electricity transfer since it was first demonstrated by Nikola Tesla in 1891. Researchers and engineers have had 130 years to find the answer to “automated charging,” and they’ve made some great strides in the last 20 years … Qi included. It’s a technology that works for many applications, but clearly it has its limitations. Now is the time to seriously turn to high frequency radio waves for at a distance power transfer.
Curious about how you can leverage wireless power technology to advance your organization? We’d love to hear from you.
For more information, here's Apple’s ‘About potential magnetic interference with medical devices’ warning, visit: https://support.apple.com/en-us/HT211900
