[…] so why were only Apple phones affected?
The answer, it seems, is because Apple recently defected from traditional quartz-based clocks in its phones in favor of clocks that are also made of MEMS silicon. Given that clocks are the most critical device in any computer and are necessary to make the CPU function, their disruption with helium atoms is enough to crash the device.
In this case, the leaking helium from the MRI machine infiltrated the iPhones like a “tiny grain of sand” and caused the MEMS clocks to go haywire.
https://en.m.wikipedia.org/wiki/Microelectromechanical_system_oscillator
Interesting
MEMS oscillators incorporate MEMS resonators, which are microelectromechanical structures that define stable frequencies. MEMS clock generators are MEMS timing devices with multiple outputs for systems that need more than a single reference frequency. MEMS oscillators are a valid alternative to older, more established quartz crystal oscillators, offering better resilience against vibration and mechanical shock, and reliability with respect to temperature variation.
So the helium causes physical interference by leaking into the housing?
Yup. Helium is such a tiny thing it can diffuse through almost anything, and in MEMS oscillators which are supposed to be at a rock solid 32kHz, causes variance in the frequency eventually just “gumming” it up entirely and causing it to stop working.
If you want to know how and why, Applied Science did a video on it. Five years ago. Because that’s when this leak happened.
Helium doesn’t just kill apple devices, It kills anything with a MEMS oscillator. Helium atoms are so small that it’s impossible to make a seal that completely blocks them.
Well that’s not true. It’s just a real bitch. As a welder, helium leak check is about the toughest damn QC to pass. Most welding QC has some reasonable margin for error during inspection, but the damn helium doesn’t care. You can have a beautiful weld with a tiny imperfection at the start or end and it’ll piss helium just as badly as an entirely scuffed bead.
