BackTrack: 2D Back-of-device Interaction Through Front Touchscreen


We present BackTrack, a trackpad placed on the back of a smartphone to track fine-grained finger motions. Our system has a small form factor, with all the circuits encapsulated in a thin layer attached to a phone case. It can be used with any off-the-shelf smartphone, requiring no power supply or modification of the operating systems. BackTrack simply extends the finger tracking area of the front screen, without interrupting the use of the front screen. It also provides a switch to prevent unintentional touch on the trackpad. All these features are enabled by a battery-free capacitive circuit, part of which is a transparent, thin-film conductor coated on a thin glass and attached to the front screen. To ensure accurate and robust tracking, the capacitive circuits are carefully designed. Our design is based on a circuit model of capacitive touchscreens, justified through both physics-based finite-element simulation and controlled laboratory experiments. We conduct user studies to evaluate the performance of using BackTrack. We also demonstrate its use in a number of smartphone applications.

Chang Xiao
Columbia University, New York, New York, United States
Karl Bayer
Snap Inc., New York, New York, United States
Changxi Zheng
Columbia University, New York, New York, United States
Shree K. Nayar
Snap, New York, New York, United States




会議: CHI 2021

The ACM CHI Conference on Human Factors in Computing Systems (

セッション: Vision and Sensing

[A] Paper Room 10, 2021-05-12 17:00:00~2021-05-12 19:00:00 / [C] Paper Room 10, 2021-05-13 09:00:00~2021-05-13 11:00:00 / [B] Paper Room 10, 2021-05-13 01:00:00~2021-05-13 03:00:00
Paper Room 10
13 件の発表
2021-05-12 17:00:00
2021-05-12 19:00:00