Explain why do our fingers leave marks on touchscreen devices?

Composition and properties of fingerprints

Our fingerprints are those small ridges and valleys that form unique patterns at the tips of our fingers. They appear as early as the formation of the fetus in the womb and do not change throughout our lives. The unique combination of these ridges comes from genetic factors, as well as the small movements or pressures we experience even before we are born. Mainly composed of skin grooves, they contain numerous sweat glands that continuously produce slight amounts of sweat and oil, thereby leaving characteristic marks with every touch. It is precisely this unique mixture of sweat, sebum, and sometimes dirt that explains why we can see our fingerprints so clearly on smooth or shiny surfaces, like phone screens.

Why do our fingers transfer residue onto touch surfaces?

The skin on our fingers naturally produces sebum, a type of oil made by small glands under the skin. When touching the screen, this greasy substance transfers directly to the surface. In addition to that, our fingers constantly carry some sweat and microscopic particles of dirt or dust accumulated throughout the day. As a result, with every touch on the touchscreen, we leave behind this discreet yet persistent cocktail of grease, moisture, and microdebris. That’s why we quickly see all these visible marks on our favorite devices.

How does interaction with screens promote the appearance of visible traces?

Every time our finger touches or glides over a touchscreen, we create a slight deposit from the substances naturally present on the skin. As our fingers regularly produce sebum (a natural oil), their repeated contact with a shiny surface like a screen leads to the gradual accumulation of fine greasy layers. This layer of sebum acts somewhat like a fingerprint, capturing dust and various dirt, making the marks more visible. Additionally, the pressure exerted by the fingers facilitates the transfer of this thin oily film and highlights these marks, which become particularly apparent under certain lights or reflections.

Factors exacerbating the accumulation of fingerprints on touchscreens

Some factors make our touch screens even more sensitive to fingerprints. For example, oily or damp skin significantly increases the transfer of residues onto the touch surface, leaving more visible marks. Frequent use of cosmetics and hand creams also accentuates the phenomenon. Similarly, warm or humid environments make our fingers sweatier, facilitating the appearance of smudges on the screen. A screen with a glossy finish attracts greasy residues even more, unlike matte screens, which often reduce the visual impact of fingerprints. Ultimately, the more frequently the screen is used and the less it is cleaned, the more visible and bothersome the fingerprints become.

Simple techniques to limit fingerprints left behind

First, basic gestures: regularly wipe the screen with a microfiber cloth. It quickly picks up smudges without scratching. Next, remember to wash your hands more often: less oil and dirt equals fewer marks. Otherwise, you can opt for special anti-smudge protectors made with oil-repellent coatings that naturally repel oils. Another tip, adjust your screen brightness: marks appear less visible on a brighter screen. Lastly, a simple trick, use a stylus; it's practical and clean, which simply avoids having your fingers constantly stuck to the screen.