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Information about the touch ui and tactile feedback for touch screen phone

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Created: rahulvala (18 Nov 2008)
Last edited: hamishwillee (31 Jul 2012)



I present the design, implementation, and informal evaluation of tactile interfaces for small touch screens used in mobile devices. I embedded a tactile apparatus in a touch screen and enhanced its basic GUI elements with tactile feedback. Instead of observing the response of interface controls, users can feel it with their fingers as they press the screen. In informal evaluations, tactile feedback was greeted with enthusiasm. I believe that tactile feedback will become the next step in touch screen interface design and a standard feature of future mobile devices.


Touch screens have become common in mobile devices, such as PDAs, digital video cameras, high-end remote controls, etc. Touch screens are attractive because they save space on mobile devices by combining the display and input space and allow dynamic simulation of electromechanical controls, e.g. buttons and switches. They provide high levels of immediacy in interaction by allowing the user to touch, push, and drag information directly with their fingers. This directness translates into better user acceptance, ease of use and a faster input rate. With this, the use of touch screens will certainly grow in the future. Despite progress, one important challenge still remains: it is difficult to provide users with sufficient feedback.Touch screen graphical buttons cannot provide the same level of haptic response as real switches, where we can directly feel the action. Without haptics, the user can only rely on audio and visual feedback, which breaks the rule of directness in touch screen interaction. Furthermore, small display size, outside noise, social restrictions, interruptions and demands of real world tasks make visual and audio feedback significantly less effective in mobile applications.

Important design features

Important design features are:

1. Actuation of the touch screen

When a signal is applied, actuators bend rapidly, pushing the touch-sensitive glass plate towards the userʼs finger. Because the actuators are very thin. we could embed them inside the touch screen. Therefore, only the lightweight touch-sensitive glass is actuated, not the entire touch screen unit which includes a heavy TFT display. Hence, we can produce sufficient tactile sensation with very little force and power. Also, actuators do not significantly increase the distance between the glass and the TFT display, avoiding the parallax problem which makes precise target selection difficult.

2. Localized tactile feedback

Vibration of touch screen glass produces tactile sensations only to the touching finger, not to the hand holding the device. To prevent the entire device from vibrating, a soft silicon damper is installed between the glass panel and frame ridges. It allows the glass panel to move when pushed by the actuators while cushioning the impact on the device frame. In addition, it seals the display from dust.

3. Small high-speed displacement

Although the displacement of actuators is small (about 0.05 mm), its fast acceleration produces a very strong tactile sensation.

4. Silent operation

Large audible noise defeats the purpose of tactile display. Noise can be sharply reduced, i.e. prevent loose parts from rattling when the actuators move.

5. Reliability

Bending the fragile ceramic actuators more then 0.1 mm by pushing on the glass can damage them. Therefore, a stopper is placed under the actuators to prevent their excessive bending.


I believe that touch screen haptic opens many new and exciting possibilities in interface design for portable devices and hope it will become a standard feature of future mobile computing devices.

This page was last modified on 31 July 2012, at 07:18.
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