While the most common way to disable a smartphone is to damage the screen, a close second is to drop the smartphone in liquid (or spill something on it).
It is a common problem that hardware manufacturers assemble small devices that react to water.
Called Liquid Contact Indicators (LCI), these are small, color-changing stickers that are placed in various places inside a device — usually near ports, SIM card slots, and other water access points.
These are used not only to indicate that water has actually entered a device, but also to know how far the water has spread.
LCIs are used on a variety of devices, from smartphones and tablets to portable game consoles.
Anything that people are likely to drop down the toilet.
Here are the LCI stickers Apple used in iPhones a few years ago (these were used from the iPhone 8 to iPhone X). Apple still uses LCI stickers in its devices, but they vary in size and location.
These things are small, smaller than a grain of rice.
When they encounter water, they change from white to red. What happens here is that exposure to water causes the white coating on the top of the sticker to melt, revealing the red color underneath.
Over the years I’ve had a few questions about LCIs and what they will and won’t activate.
First of all, note that the process is irreversible and drying an LCI does not make it white again.
Another question is whether solvents such as isopropyl alcohol will activate the LCI. I have tested both 99% and 70% isopropyl alcohol and neither activates the LCI.
Some people think that if you soak an LCI in isopropyl alcohol, it will stop turning red when exposed to water. This is not true; the LCI remains active.
Do carbonated drinks activate LCIs? You bet they do!
Finally, does being in a humid environment lead to LCIs? I put one in a bag, breathed into it so there was condensation in the bag, and positioned it so the LCI didn’t hit any surface with condensation. After more than an hour, the LCI remained white.
If you have an iPhone, you can see one LCI by removing the SIM tray and looking in the slot for the white dot (hopefully at least it’s still white!)