Back-of-device touch input can enable pointing
input on very small screens. This enables building new types of devices,
such as touch-capable electronic jewelry. Here are four of the back-of-device designs we envision
(a) pendant, (b) clip-on (b) watch, and (b) ring. Screen diagonals range
from 2.5" to less than half an inch.
We explore how to add pointing input capabilities to very small screen devices. On first sight, touch-screens seem to allow for particular compactness, because they integrate input and screen into the same physical space. The opposite is true, however, because the user’s fingers occlude contents and prevent precision.
So while touch was shown to work well for 3"+ screens, the size of these
devices makes them hard to carry while physically active or with
fashionable clothing. A half- or quarter size touch screen
device, in contrast, is limited to a small number of on-screen objects
and/or requires a stylus (e.g.
We argue that the key to touch-enabling very small devices is to use touch on the device backside. In order to study this, we have created
the 2.4” prototype device shown below; we simulate screens smaller than that by masking the screen.
In a user study, participants completed a pointing task successfully across
all (2.4" to 0.3") display sizes when using a back-of device interface. The touchscreen-based control condition (enhanced with the
shift technique), in contrast, failed for screen diagonals below 1 inch.
A second study provides design guidelines for practitioners who want to
design for back-of-device interaction (details:
CHI 2009 paper).
In collaboration primarily with
during his summer 2008 internship at MSR,
as well as
with Roz Ho, Georg Petschnigg, David Wykes, and many
others at Microsoft. Nano touch is related