[…] 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.
Yup. Most of the mems devices will essentially shut down the device if they go out of tolerance. This is a pretty common-knowledge fact among folks who work with large magnets, or with helium or hydrogen gas.
Funnily enough, it also happens with equipment microcontrollers which are unlikely to have a MEMS unit in them – for instance, any benchtop centrifuge made after the mid-90s will shut down, and I’m pretty sure those are still on quartz clocks. It also effects things like on-chip thermometers.
