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BackXPress: Using Back-of-Device Finger Pressure to Augment Touchscreen Input on Smartphones

Published: 02 May 2017 Publication History

Abstract

When people hold their smartphone in landscape orientation, they use their thumbs for input on the frontal touchscreen, while their remaining fingers rest on the back of the device (BoD) to stabilize the grip. We present BackXPress, a new interaction technique that lets users create BoD pressure input with these remaining fingers to augment their interaction with the touchscreen on the front: Users can apply various pressure levels with each of these fingers to enter different temporary "quasi-modes" that are only active as long as that pressure is applied. Both thumbs can then interact with the frontal screen in that mode. We illustrate the practicality of BackXPress with several sample applications, and report our results from three user studies: Study 1 investigated which fingers can be used to exert BoD pressure and found index, middle, and ring finger from both hands to be practical. Study 2 revealed how pressure touches from these six fingers are distributed across the BoD. Study 3 examined user performance for applying BoD pressure (a) during single touches at the front and (b) for 20 seconds while touching multiple consecutive frontal targets. Participants achieved up to 92% pressure accuracy for three separate pressure levels above normal resting pressure, with the middle fingers providing the highest accuracy. BoD pressure did not affect frontal touch accuracy. We conclude with design guidelines for BoD pressure input.

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    cover image ACM Conferences
    CHI '17: Proceedings of the 2017 CHI Conference on Human Factors in Computing Systems
    May 2017
    7138 pages
    ISBN:9781450346559
    DOI:10.1145/3025453
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    Published: 02 May 2017

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    Author Tags

    1. back-of-device
    2. bimanual input
    3. pressure
    4. smartphone

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    • (2025)Study on Finger Gesture Interface Using One-Channel EMGIEEE Access10.1109/ACCESS.2025.352768413(9606-9614)Online publication date: 2025
    • (2024)Pressure-Based Menu Selection on a Spherical Tangible DeviceExtended Abstracts of the CHI Conference on Human Factors in Computing Systems10.1145/3613905.3651090(1-6)Online publication date: 11-May-2024
    • (2024)PaperTouch: Tangible Interfaces through Paper Craft and Touchscreen DevicesProceedings of the 2024 CHI Conference on Human Factors in Computing Systems10.1145/3613904.3642571(1-15)Online publication date: 11-May-2024
    • (2024)Evaluating an In-Hand Ball-Shaped Controller for Object Manipulation in Virtual Reality2024 IEEE Conference Virtual Reality and 3D User Interfaces (VR)10.1109/VR58804.2024.00025(10-19)Online publication date: 16-Mar-2024
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    • (2023)An exploration of pressure input with bare finger for Mobile interaction in stationary and Mobile situationsMultimedia Tools and Applications10.1007/s11042-023-14503-082:17(25711-25731)Online publication date: 14-Feb-2023
    • (2022)TetraForce: A Magnetic-Based Interface Enabling Pressure Force and Shear Force Input Applied to Front and Back of a SmartphoneProceedings of the ACM on Human-Computer Interaction10.1145/35677176:ISS(185-206)Online publication date: 14-Nov-2022
    • (2022)MicroPress: Detecting Pressure and Hover Distance in Thumb-to-Finger InteractionsProceedings of the 2022 ACM Symposium on Spatial User Interaction10.1145/3565970.3567698(1-10)Online publication date: 1-Dec-2022
    • (2021)TapNet: The Design, Training, Implementation, and Applications of a Multi-Task Learning CNN for Off-Screen Mobile InputProceedings of the 2021 CHI Conference on Human Factors in Computing Systems10.1145/3411764.3445626(1-11)Online publication date: 6-May-2021
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