Your Phone Has a Tiny, Crucial Design Detail You’ve Probably Never Even Noticed

The small stripes of plastic along a smartphone’s outer edge are one of its most important features.

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Chandler Bondurant

Welcome to Further Details, a series dedicated to ubiquitous but overlooked elements hidden on your favorite products. This week: the strips of plastic hiding on your smartphone.

For years and years, after the death of the flip phone and slide-out physical keyboard, most smartphones have looked pretty much the same: smooth slabs of metal or glass, with a camera on the back, and ever fewer buttons. But there’s one crucial, subtle aspect of this simple, shared design that you may not have noticed.

Take a second and turn your phone over in your hands a few times. Can you find a few small lines of colored plastic around the edge? These are one of the most crucial bits of engineering on your pocket supercomputer, without which it could not function.


These bits of plastic are “antenna lines,” and you may be familiar with them from their particularly obvious placement on phones like the iPhone 6 and, if you are an old-head Android nerd, the HTC One.

While they are opaque plastic, they actually function as tiny windows, not for light but rather for the radio waves that come from your phone’s internal Bluetooth, Wi-Fi, and LTE/5G antennas and connect you to the internet. These electromagnetic waves that let your phone function as an actual communication device are able to move relatively effortlessly through materials that do not conduct electricity (like plastic) but are blocked by materials that do (like metal). These subtle little bars are what the data into and out of your phone.

Not all phones need these lines, of course. Phone that are already made of plastic are very transparent to radio waves. Similarly, glass will allow radio waves through, though not as readily as plastic, and phones with glass backs frequently have a metal frame, which will still contain a few small antenna lines.

Antenna lines are not a magic bullet for phone design, and can be thwarted by your body, which blocks signals quite effectively! Perhaps the most well known example of this problem was with Apple’s glass-backed iPhone 4, and the ensuing “antennagate,” where the placement of the antenna lines along the phone’s metal frame were such that a user’s hand could easily bridge the gap and interfere with the signal.

So the next time you have trouble getting your fancy all-metal phone to establish a solid internet connect, keep an eye out for this little lines and make sure you aren’t covering them up. They might be tiny, and a little unsightly, but they’re the reason your phone isn’t just a calculator.

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