十万个为什么·科学启蒙30篇（2）

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触摸屏究竟是如何工作的？

Most smartphones use capacitive touchscreens, which rely on the fact that your finger conducts electricity better than air or glass.
A grid of transparent electrodes sits beneath the screen surface, and a constant low-voltage charge flows across it evenly.
When your finger touches the screen, it draws a tiny amount of current from nearby points, changing the local electrostatic field.
The device detects these changes in capacitance at multiple points and calculates the exact touch location using algorithms.
Unlike older resistive screens — which needed pressure to press two layers together — capacitive screens respond to light taps and even gloved fingers with special conductive thread.
Multi-touch capability allows zooming, rotating, and swiping because the system tracks several contact points simultaneously.
Water or metal objects can confuse capacitive sensors, which is why screens sometimes misbehave near wet hands or metal surfaces.
Future screens may use ultrasound or optical sensors to detect hovering gestures without any physical contact at all.