touchscreenTouchscreens are becoming the predominant means of controlling devices of all kinds, including medical devices. It seems that more and more products are abandoning traditional hardware controls – push buttons, switches, sliders, knobs, etc. – for touchscreens. But current touchscreens have a serious drawback that makes them problematic to use and often frustrates the user. They don’t offer the type of tactile feedback that traditional controls do.

There are some systems that do incorporate haptic feedback via vibration, and that is certainly a step in the right direction. But to reach the level of feedback that traditional controls provide, there needs to be more. Providing a vibration or audible click (or both) is relatively effective for pushbutton-type action. But for sliding and rotating actions, I know of no technology that can offer the resistance and frictional characteristics of a mechanical slider or knob. Resistance and friction allow the user to operate controls with precision. Being able to achieve controlled, precise movement is the biggest drawback of using touchscreen controls. The resistance and friction that touchscreens do provide – the resistance of the skin of the fingertip on the glass touchscreen surface – actually works to the detriment of precision. The force required to overcome the friction tends to lead the user to overcompensate the amount of movement they are trying to achieve, causing them to have to awkwardly readjust.

There have been some attempts at designing touchscreens that allow their surfaces to change – layered screens that can produce raised surfaces or indentions to provide the tactile feel of a button. The technology from Tactus is one example. Effective for pushbuttons and keyboard keys, but not so much for sliders and rotating knobs.

Ultimately, touchscreen controls would be vastly improved if a means of providing tactile resistance could be achieved. For medical devices, there remains the problem of keeping the screen surface clean so it doesn’t become a conduit for infection. That’s for another time.