Remote tactile feedback on interactive surfaces

Direct touch input on interactive surfaces has become a
predominating standard for the manipulation of digital information
in our everyday lives. However, compared to our rich interchange
with the physical world, the interaction with touch-based systems
is limited in terms of flexibility of input and expressiveness of
output. Particularly, the lack of tactile feedback greatly reduces
the general usability of a touch-based system and hinders from a
productive entanglement of the virtual information with the
physical world. This thesis proposes remote tactile feedback as a
novel method to provide programmed tactile stimuli supporting
direct touch interactions. The overall principle is to spatially
decouple the location of touch input (e.g. fingertip or hand) and
the location of the tactile sensation on the user's body (e.g.
forearm or back). Remote tactile feedback is an alternative concept
which avoids particular challenges of existing approaches.
Moreover, the principle provides inherent characteristics which can
accommodate for the requirements of current and future touch
interfaces. To define the design space, the thesis provides a
structured overview of current forms of touch surfaces and
identifies trends towards non-planar and non-rigid forms with more
versatile input mechanisms. Furthermore, a classification
highlights limitations of the current methods to generate tactile
feedback on touch-based systems. The proposed notion of tactile
sensory relocation is a form of sensory substitution. Underlying
neurological and psychological principles corroborate the approach.
Thus, characteristics of the human sense of touch and principles
from sensory substitution help to create a technical and conceptual
framework for remote tactile feedback. Three consecutive user
studies measure and compare the effects of both direct and remote
tactile feedback on the performance and the subjective ratings of
the user. Furthermore, the experiments investigate different body
locations for the application of tactile stimuli. The results show
high subjective preferences for tactile feedback, regardless of its
type of application. Additionally, the data reveals no significant
differences between the effects of direct and remote stimuli. The
results back the feasibility of the approach and provide parameters
for the design of stimuli and the effective use of the concept. The
main part of the thesis describes the systematical exploration and
analysis of the inherent characteristics of remote tactile
feedback. Four specific features of the principle are identified:
(1) the simplification of the integration of cutaneous stimuli, (2)
the transmission of proactive, reactive and detached feedback, (3)
the increased expressiveness of tactile sensations and (4) the
provision of tactile feedback during multi-touch. In each class,
several prototypical remote tactile interfaces are used in
evaluations to analyze the concept. For example, the PhantomStation
utilizes psychophysical phenomena to reduce the number of single
tactile actuators. An evaluation with the prototype compares
standard actuator technologies with each other in order to enable
simple and scalable implementations. The ThermalTouch prototype
creates remote thermal stimuli to reproduce material
characteristics on standard touchscreens. The results show a stable
rate of virtual object discrimination based on remotely applied
temperature profiles. The AutmotiveRTF system is implemented in a
vehicle and supports the driver's input on the
in-vehicle-infotainment system. A field study with the system
focuses on evaluating the effects of proactive and reactive
feedback on the user's performance. The main contributions of the
dissertation are: First, the thesis introduces the principle of
remote tactile feedback and defines a design space for this
approach as an alternative method to provide non-visual cues on
interactive surfaces. Second, the thesis describes technical
examples to rapidly prototype remote tactile feedback systems.
Third, these prototypes are deployed in several evaluations which
highlight the beneficial subjective and objective effects of the
approach. Finally, the thesis presents features and inherent
characteristics of remote tactile feedback as a means to support
the interaction on today's touchscreens and future interactive
surfaces.