On-Device Input Controls – Where to place them?

Recent smartphones incorporate a large number of input controls beyond the display on the front such as volume buttons, fingerprint scanners, and silent switches. With recent advances of foldable smartphones, the full surface of a mobile device could soon be used for inputs on mass-market devices. To help designers to find suitable and ergonomic placements for input controls beyond the touchscreen, we investigated the areas that can be reached without losing grip stability (comfortable area) and the maximum range of the fingers that do not require a grip change on four representative smartphones held in a single-handed grip.

We recorded the finger movements with a high-precision motion capture system (OptiTrack). The results of this work describes the characteristics of the comfortable area and maximum range for different phone sizes and provides four design implications for the placement of input controls to support single-handed Back-of-device and edge interaction. Amongst others, the index and middle finger are the most suited fingers for Back-of-device interaction and the grip shifts towards the top edge with increasing phone sizes. This work was presented at the ACM CHI Conference on Human Factors in Computing Systems (CHI ’18), the premier international conference in the field of Human-Computer Interaction.

A follow-up study will be published at the 21st International Conference on Human-Computer Interaction with Mobile Devices and Services (MobileHCI 2019) which also takes unintended inputs for Back-of-Device interaction into consideration.

Publications

PDF
Investigating Unintended Inputs for One-Handed Touch Interaction Beyond the Touchscreen.
Huy Viet Le, Sven Mayer, Benedict Steuerlein, and Niels Henze. 2019. In Proceedings of the 21st International Conference on Human-Computer Interaction with Mobile Devices and Services (MobileHCI '19). ACM, Taipei, Taiwan. 
@inproceedings{le2019unintended,
author = {Le, Huy Viet and Mayer, Sven and Steuerlein, Benedict and Henze, Niels},
title = {Investigating Unintended Inputs for One-Handed Touch Interaction Beyond the Touchscreen},
booktitle = {Proceedings of the 21st International Conference on Human-Computer Interaction with Mobile Devices and Services},
series = {MobileHCI '19},
year = {2019},
isbn = {978-1-4503-6825-4},
location = {Taipei, Taiwan},
pages = {34:1--34:14},
articleno = {34},
numpages = {14},
url = {http://doi.acm.org/10.1145/3338286.3340145},
doi = {10.1145/3338286.3340145},
acmid = {3340145},
publisher = {ACM},
address = {New York, NY, USA},
keywords = {Finger movement, one-handed, smartphone, touch},
}
PDF
Fingers' Range and Comfortable Area for One-Handed Smartphone Interaction Beyond the Touchscreen.
Huy Viet Le, Sven Mayer, Patrick Bader, and Niels Henze. 2018. In Proceedings of the 2018 CHI Conference on Human Factors in Computing Systems (CHI '18). ACM, Montreal QC, Canada. 
@inproceedings{le2018fingers,
author = {Le, Huy Viet and Mayer, Sven and Bader, Patrick and Henze, Niels},
title = {Fingers' Range and Comfortable Area for One-Handed Smartphone Interaction Beyond the Touchscreen},
booktitle = {Proceedings of the 2018 CHI Conference on Human Factors in Computing Systems},
series = {CHI '18},
year = {2018},
isbn = {978-1-4503-5620-6},
location = {Montreal QC, Canada},
pages = {31:1--31:12},
articleno = {31},
numpages = {12},
url = {http://doi.acm.org/10.1145/3173574.3173605},
doi = {10.1145/3173574.3173605},
acmid = {3173605},
publisher = {ACM},
address = {New York, NY, USA},
keywords = {comfortable area, finger range, one-handed, smartphone},
}

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