Backpat: Improving One-handed Touchscreen Operation by Patting the Back of the Device

We present BackPat: A technique for supporting one-handed smartphone operation. Using pats of either the index finger or middle finger or thumb on the back or side of the device, the user can extend one-handed use in a variety of difficult tasks. We explain the principle behind the technique and make a first attempt at examining its usability and versatility by implementing it into four applications, covering text selection, reaching distant targets, multiple file selection, and map and image zoom. An initial user study has shown a high grade of acceptance, verified the interaction logic and highlighted improvements in task-completion time over non-enhanced interaction. This way we hope to encourage discussion about its usefulness and potential