Back Keyboard: A backside keyboard of mobile devices using QWERTY layout

Abstract

Since smart phones adopted touchscreen, users have been enjoying large displays. However, when using soft keyboard, the available size of the display becomes less than 50%. In this paper Back Keyboard, a physical keyboard installed backside of mobile phone, is presented. Also the design process with a prototype through a series of studies is described. User evaluation was conducted with the prototype; the average text entry rate was 15.3 WPM (SD: 3.6) and the error rate was 12.2% (SD: 9.0) after a 40-minute typing session. Moreover, the text entry rates of Back Keyboard and general keyboards for PCs did not have significant relations. This means that the prototype could be used smoothly regardless of one's ability of typing on a PC.