Grip-Reach-Touch-Repeat: A Refined Model of Grasp to Encompass One-Handed Interaction with Arbitrary Form Factor Devices

We extend grasp models to encompass one-handed interaction with arbitrary shaped touchscreen devices. Current models focus on how objects are stably held by external forces. However, with touchscreen devices, we postulate that users do a trade-off between holding securely and exploring interactively. To verify this, we first conducted a qualitative study which asked participants to grasp 3D printed objects while considering its different interactivity. Results of the study confirm our hypothesis and reveal obvious change in postures. To further verify this trade-off and design interactions, we developed a simulation software capable of computing the stability of a grasp and its reachability. We conducted the second study based on the observed predominant grasps to validate our software with a glove. Results also confirm a consistent trade-off between stability and reachability. We conclude by discussing how this research can help designing computational tools focusing on hand-held interactions with arbitrary shaped touchscreen devices.