Using pressure input and thermal feedback to broaden haptic interaction with mobile devices

Pressure input and thermal feedback are two under-researched aspects of touch in mobile human-computer interfaces. Pressure input could provide a wide, expressive range of continuous input for mobile devices. Thermal stimulation could provide an alternative means of conveying information non-visually. This thesis research investigated 1) how accurate pressure-based input on mobile devices could be when the user was walking and provided with only audio feedback and 2) what forms of thermal stimulation are both salient and comfortable and so could be used to design structured thermal feedback for conveying multi-dimensional information. The first experiment tested control of pressure on a mobile device when sitting and using audio feedback. Targeting accuracy was >= 85% when maintaining 4-6 levels of pressure across 3.5 Newtons, using only audio feedback and a Dwell selection technique. Two further experiments tested control of pressure-based input when walking and found accuracy was very high (>= 97%) even when walking and using only audio feedback, when using a rate-based input method. A fourth experiment tested how well each digit of one hand could apply pressure to a mobile phone individually and in combination with others. Each digit could apply pressure highly accurately, but not equally so, while some performed better in combination than alone. 2- or 3-digit combinations were more precise than 4- or 5-digit combinations. Experiment 5 compared one-handed, multi-digit pressure input using all 5 digits to traditional two-handed multitouch gestures for a combined zooming and rotating map task. Results showed comparable performance, with multitouch being ~1% more accurate but pressure input being ~0.5sec faster, overall. Two experiments, one when sitting indoors and one when walking indoors tested how salient and subjectively comfortable/intense various forms of thermal stimulation were. Faster or larger changes were more salient, faster to detect and less comfortable and cold changes were more salient and faster to detect than warm changes. The two final studies designed two-dimensional structured ‘thermal icons’ that could convey two pieces of information. When indoors, icons were correctly identified with 83% accuracy. When outdoors, accuracy dropped to 69% when sitting and 61% when walking. This thesis provides the first detailed study of how precisely pressure can be applied to mobile devices when walking and provided with audio feedback and the first systematic study of how to design thermal feedback for interaction with mobile devices in mobile environments.