Tactile sensing in human–computer interfaces: The inclusion of pressure sensitivity as a third dimension of user input

This paper presents a review of tactile technologies for human–computer interactivity via touch interfaces, where touch force is measured as a third dimension of user input along with touch location. Until recently, tactile technologies for computing applications have detected only the location of a touch (or several touches simultaneously) with no additional information about the force or pressure the user imparts to the interface. Such additional input may open up new applications in force-enhanced gestures, for example the touch force may dictate the linewidth used in drawing software, or the speed of a scroll gesture may be increased with increasing applied force. Here we review the underlying physical principles behind several force sensitive touch technologies. The latest innovations by leading technology developers, only available in the patent literature, are also described and where public data exist the force-resistance behaviours of several key technologies are compared in terms of their sensitivity and range of response. The advantages and disadvantages of each technology are discussed, along with the current and possible future applications in consumer electronics. It is shown that the concept of pressure-sensitivity as an additional user input mechanism is fast gaining traction, with many implementations already found in commercial products. Furthermore, a study of the patent trends shows that this functionality may soon become commonplace in the new generation of consumer electronic devices.