Using shear as a supplemental two-dimensional input channel for rich touchscreen interaction

Touch input is constrained, typically only providing finger X/Y coordinates. To access and switch between different functions, valuable screen real estate must be allocated to buttons and menus, or users must perform special actions, such as touch-and-hold, double tap, or multi-finger chords. Even still, this only adds a few bits of additional information, leaving touch interaction unwieldy for many tasks. In this work, we suggest using a largely unutilized touch input dimension: shear (force tangential to a screen's surface). Similar to pressure, shear can be used in concert with conventional finger positional input. However, unlike pressure, shear provides a rich, analog 2D input space, which has many powerful uses. We put forward five classes of advanced interaction that considerably expands the envelope of interaction possible on touchscreens.