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Why Can't The Capacitive Screen Be Touched With Nails?


Published by JFCVision October 15,2019

Most of the touch screens were touched with nails 10 years ago, but because the nails are too hard, it is easy to scratch the touch screen, and the nails are not very convenient to move.

such as wearing gloves, it is inconvenient, then the capacitive touch screen The appearance can be touched without touching the nails and directly with your fingers

But many people find that capacitive touch screens become insensitive when they touch the screen with their nails. Why?


capacitive touch screen


Most smartphone screens now use capacitive touch screens

When the finger touches the metal layer, the user and the touch screen surface form a coupling capacitor due to the human body electric field. 

For high-frequency current, the capacitor is a direct conductor. The finger draws a small current from the contact point.

This current flows out from the electrodes on the four corners of the touch screen, and the current flowing through the four electrodes is proportional to the distance from the finger to the four corners. 

The controller calculates the position of the touchpoint by accurately calculating the ratio of the four currents. 

Therefore, as long as the material and the screen of the mobile phone are used to create a capacitor, the conductors such as apple peel, watermelon rind, banana peel, etc. can slide the screen of the mobile phone.


The nail is insulated and is equivalent to a dielectric. The tissue under the human skin has a large water content, and the cell fluid tissue fluid can constitute a conductive structure. Therefore, the capacitive touch screen cannot be swiped with the nail.


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