this post was submitted on 16 Jul 2024
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Oh, I did a dumb. Capacitive readers use the body's natural electrical signal to form an image of your fingerprint. You can trick them by using something conductive and running the right amount of electricity through.
Dead people don't work though. Not for very long at least.
Capacitive sensors are looking at capacitance of a material, everything has this not just living things and it certainly doesn't require putting current through the material. You can for example get capacitive sensors for sensing the presence of cardboard, and they're often used for detecting metal parts (obviously tuned to the specific material). This is also why water droplets mess up touch screens (and the biometric sensor), because it's close enough to the capacitance of a finger (we're mostly water after all) to trick it and create false triggers.
Capacitive sensors don't measure the body's signals. Capacitance is a physical property of a material. The sensor puts out a signal and measures the response.
I can use a gallon of milk to scroll my phone. Just tried.