BackTap: robust four-point tapping on the back of an off-the-shelf smartphone

  • Authors:

  • Cheng Zhang;Aman Parnami;Caleb Southern;Edison Thomaz;Gabriel Reyes;Rosa Arriaga;Gregory D. Abowd

  • Affiliations:

  • Georgia Institute of Technology, Atlanta, GA, USA;Georgia Institute of Technology, Atlanta, GA, USA;Georgia Institute of Technology, Atlanta, GA, USA;Georgia Institute of Technology, Atlanta, GA, USA;Georgia Institute of Technology, Atlanta, GA, USA;Georgia Institute of Technology, Atlanta, GA, USA;Georgia Institute of Technology, Atlanta, GA, USA

  • Venue:
  • Proceedings of the adjunct publication of the 26th annual ACM symposium on User interface software and technology
  • Year:
  • 2013

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Abstract

We present BackTap, an interaction technique that extends the input modality of a smartphone to add four distinct tap locations on the back case of a smartphone. The BackTap interaction can be used eyes-free with the phone in a user's pocket, purse, or armband while walking, or while holding the phone with two hands so as not to occlude the screen with the fingers. We employ three common built-in sensors on the smartphone (microphone, gyroscope, and accelerometer) and feature a lightweight heuristic implementation. In an evaluation with eleven participants and three usage conditions, users were able to tap four distinct points with 92% to 96% accuracy.