Erik Wooldridge, a systems specialist at a Chicago medical hospital, recently detailed a "bizarre" incident where every iPhone and Apple Watch at the facility was completely disabled after a mishap occurred when testing an MRI machine made by GE.
According to Wooldridge, who goes by 'harritaco' on Reddit, his CTO was "freaking out" after the mass iPhone outage, fearing that other computer equipment at the data center may have also failed.
However, he found only Apple's mobile devices were affected. Android devices escaped unscathed.
The cause, apparently, was helium -- a lot of it -- but the system specialist still didn't understand why only Apple devices were affected.
"GE claims that the helium is what impacts the iOS devices, which makes absolutely no sense to me. I know liquid helium is used as a coolant for the super-conducting magnets, but why would it only effect Apple devices?" wrote Wooldridge.
Apparently 120 liters of liquid helium had leaked out over five hours after a new magnet had been installed in the MRI machine. It wasn't in a sealed room, so the helium spread throughout the facility, gradually taking down everyone's iOS devices.
"We do not know how much of the 120 liters ended up going outdoors and how much ended up inside. Helium expands about 750 times when it expands from a liquid to a gas, so that's a lot of helium," Wooldridge wrote.
One commenter, Captain Cool, noted the impact helium has on 'microelectromechanical system' or MEMS oscillators, the tiny mechanical devices that drive the clock in modern processors.
"These are barely visible mechanical systems that resonate at some designed frequency, and include packaging to convert this resonance into a useful electrical clock signal," wrote Captain Cool.
But the mechanical resonator must be inside a hermetically sealed chamber, and those hermetic seals are "somewhat commonly permeable to small atomic gasses such as helium", according to Captain Cool.
Captain Cool links to a page on computer clock maker SiTime's website that acknowledges helium and hydrogen can permeate its seal, which is otherwise impervious to nitrogen and oxygen.
"Apple devices probably share a common family of MEMS resonator to reduce manufacturing costs," theorized Captain Cool.
"This clock likely leaks in helium-rich atmospheres, pushing the output frequency outside the bounds that the main processors are designed to handle, rendering them non-functional."
Kyle Wiens, CEO and co-founder of teardown and repair specialist, iFixit, has now given his take on why Apple mobile devices are "allergic to helium" and confirms that Apple recently started using SiTime's MEMS oscillators as a means of creating thinner mobile devices.
Wooldridge told Wiens the affected iOS devices were "completely dead" and didn't appear to be charging when plugged in.
Also, only iPhone 6 and higher were affected, as well as Apple Watch Series 0 and higher. An iPhone 5 was not affected.
As noted by Wiens, Apple recently started using MEMS timing oscillators from SiTime to replace quartz oscillators because the former are smaller, leading to slimmer devices.
"Specifically, they're using the SiT512, 'the world's smallest, lowest power 32kHz oscillator'. And if the MEMS device was susceptible to helium intrusion, that could be our culprit," writes Wiens.
He tested the helium theory using an iPhone 8 in iFixit's lab and found it lasted four minutes in a helium atmosphere before completely shutting down.
Apple's user guide also notes -- without explaining the connection to MEMS oscillators -- that exposing an iPhone to high concentrations of "near evaporating liquefied gasses such as helium, may damage or impair iPhone functionality".
Google's Pixel 3 could also be affected by a similar exposure to helium gas because of its use of InvenSense Motion's MEMS-based sensors.
According to the company, helium exposure could cause its gyro and pressure sensors to stop working, while the gas wouldn't impact its accelerometers. The helium-vulnerable components should recover after leaving a helium environment.
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