Evaluating different types of actuators for Liquid Screen Overlays (LSO)

In this paper we have evaluated various electromagnetic and piezoelectric actuators, originally designed for indirect haptic interaction on touchscreen mobile devices, using a transparent Liquid Screen Overlay (LSO). In line with our previous work with mediation of haptic signals, this research focuses on methods of attenuating acoustic components (noise) while providing enhanced vibrotactile feedback signals on mobile devices. Utilizing our previously developed unique transparent LSO, we evaluate various actuators' ability to generate haptic feedback as well as to limit acoustic noise. The LSO developed for this study is an advanced version of our previous work and contains a siloxane-based lubricant composition (a low viscosity inert nonconductive liquid), that acts as a soft deformable covering for the capacitive touchscreen on an ExoPC tablet, enhancing the ratio between tactile signals and the acoustic components, provided by haptic actuators. Using surface mounted and embedded actuators within the LSO; we recorded the vertical and horizontal micro-displacements for a range of frequencies (60-240Hz). Using this data, each actuator was evaluated for its ability to create vibrotactile signals and transmit them, to the point of contact on the LSO.