· FINGER STRESS: An ergonomic problem of touchscreen is their stress on human fingers when used for more than a few minutes at a time, since significant pressure can be required for certain types of touchscreen. This can be alleviated for some users with the use of a pen or other device to add leverage and more accurate pointing. The introduction of such items can sometimes be problematic, depending on the desired use (e.g. public kiosks such as ATMs).
· FINGER PRINTS: Touchscreen can suffer from the problem of fingerprints on the display. This can be mitigated by the use of materials with optical coating designed to reduce the visible effects of fingerprint oils, such as the oleo phobic coating used in the iPhone, 3G S, or by reducing skin contact by using a fingernail or stylus.
· FINGERNAIL AS STYLUS: These ergonomic issues of direct touch can be bypassed by using a different technique, provided that the user's fingernails are either short or sufficiently long. Rather than pressing with the soft skin of an outstretched fingertip, the finger is curled over, so that the tip of a fingernail can be used instead. The thumb is optionally used to provide support for the finger or for a long fingernail, from underneath. This method does not work on capacitive touch screens.
The fingernail's hard, curved surface contacts the touchscreen at one very small point. Therefore, much less finger pressure is needed, much greater precision is possible (approaching that of a stylus, with a little experience), much less skin oil is smeared onto the screen, and the fingernail can be silently moved across the screen with very little resistance, allowing for selecting text, moving windows, or drawing lines.
The human fingernail consists of keratin which has a hardness and smoothness similar to the tip of a stylus (and so will not typically scratch a touchscreen). Alternately, very short stylus tips are available, which slip right onto the end of a finger; this increases visibility of the contact point with the screen.
· FINGERPRINTS: Touchscreens can suffer from the problem of fingerprints on the display. This can be mitigated by the use of materials with optical coating designed to reduce the visible effects of fingerprint oils, such as the oleo phobic coating used in the iPhone 3G S, or by reducing skin contact by using a fingernail or stylus.
· COMBINED WITH HEPTICS: The user experience with touchscreens without tactile feedback or haptics can be difficult due to latency or other factors. Research from the University of Glasgow Scotland [Brewster, Chohan, and Brown 2007] demonstrates that sample users reduce input errors (20%), increase input speed (20%), and lower their cognitive load (40%) when touchscreens are combined with haptics or tactile feedback, [vs. non-haptic touchscreens].
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