A Review of Smart Materials in Tactile Actuators for Information Delivery

As the largest organ in the human body, the skin provides the important sensory channel for humans to receive external stimulations based on touch. By the information perceived through touch, people can feel and guess the properties of objects, like weight, temperature, textures, and motion, etc. In fact, those properties are nerve stimuli to our brain received by different kinds of receptors in the skin. Mechanical, electrical, and thermal stimuli can stimulate these receptors and cause different information to be conveyed through the nerves. Technologies for actuators to provide mechanical, electrical or thermal stimuli have been developed. These include static or vibrational actuation, electrostatic stimulation, focused ultrasound, and more. Smart materials, such as piezoelectric materials, carbon nanotubes, and shape memory alloys, play important roles in providing actuation for tactile sensation. This paper aims to review the background biological knowledge of human tactile sensing, to give an understanding of how we sense and interact with the world through the sense of touch, as well as the conventional and state-of-the-art technologies of tactile actuators for tactile feedback delivery

Tactons: structured tactile messages for non-visual information display

Tactile displays are now becoming available in a form that can be easily used in a user interface. This paper describes a new form of tactile output. Tactons, or tactile icons, are structured, abstract messages that can be used to communicate messages non-visually. A range of different parameters can be used for Tacton construction including: frequency, amplitude and duration of a tactile pulse, plus other parameters such as rhythm and location. Tactons have the potential to improve interaction in a range of different areas, particularly where the visual display is overloaded, limited in size or not available, such as interfaces for blind people or in mobile and wearable devices. This paper describes Tactons, the parameters used to construct them and some possible ways to design them. Examples of where Tactons might prove useful in user interfaces are given

Crossmodal audio and tactile interaction with mobile touchscreens

Touchscreen mobile devices often use cut-down versions of desktop user interfaces placing high demands on the visual sense that may prove awkward in mobile settings. The research in this thesis addresses the problems encountered by situationally impaired mobile users by using crossmodal interaction to exploit the abundant similarities between the audio and tactile modalities. By making information available to both senses, users can receive the information in the most suitable way, without having to abandon their primary task to look at the device. This thesis begins with a literature review of related work followed by a definition of crossmodal icons. Two icons may be considered to be crossmodal if and only if they provide a common representation of data, which is accessible interchangeably via different modalities. Two experiments investigated possible parameters for use in crossmodal icons with results showing that rhythm, texture and spatial location are effective. A third experiment focused on learning multi-dimensional crossmodal icons and the extent to which this learning transfers between modalities. The results showed identification rates of 92% for three-dimensional audio crossmodal icons when trained in the tactile equivalents, and identification rates of 89% for tactile crossmodal icons when trained in the audio equivalent. Crossmodal icons were then incorporated into a mobile touchscreen QWERTY keyboard. Experiments showed that keyboards with audio or tactile feedback produce fewer errors and greater speeds of text entry compared to standard touchscreen keyboards. The next study examined how environmental variables affect user performance with the same keyboard. The data showed that each modality performs differently with varying levels of background noise or vibration and the exact levels at which these performance decreases occur were established. The final study involved a longitudinal evaluation of a touchscreen application, CrossTrainer, focusing on longitudinal effects on performance with audio and tactile feedback, the impact of context on performance and personal modality preference. The results show that crossmodal audio and tactile icons are a valid method of presenting information to situationally impaired mobile touchscreen users with recognitions rates of 100% over time. This thesis concludes with a set of guidelines on the design and application of crossmodal audio and tactile feedback to enable application and interface designers to employ such feedback in all systems

Active PinScreen: Exploring Spatio-Temporal Tactile Feedbackfor Multi-Finger Interaction

Multiple fingers are often used for efficient interaction with handheld computing devices. Currently, any tactile feedback provided is felt on the finger pad or the palm with coarse granularity. In contrast, we present a new tactile feedback technique, Active PinScreen, that applies localised stimuli on multiple fingers with fine spatial and temporal resolution. The tactile screen uses an array of solenoid-actuated magnetic pins with millimetre scale form-factor which could be deployed for back-of-device handheld use without instrumenting the user. As well as presenting a detailed description of the prototype, we provide the potential design configurations and the applications of the Active PinScreen and evaluate the human factors of tactile interaction with multiple fingers in a controlled user evaluation. The results of our study show a high recognition rate for directional and patterned stimulation across different grip orientations as well as within- and between- fingers. We end the paper with a discussion of our main findings, limitations in the current design and directions for future work

Do That, There: An Interaction Technique for Addressing In-Air Gesture Systems

When users want to interact with an in-air gesture system, they must first address it. This involves finding where to gesture so that their actions can be sensed, and how to direct their input towards that system so that they do not also affect others or cause unwanted effects. This is an important problem [6] which lacks a practical solution. We present an interaction technique which uses multimodal feedback to help users address in-air gesture systems. The feedback tells them how (“do that”) and where (“there”) to gesture, using light, audio and tactile displays. By doing that there, users can direct their input to the system they wish to interact with, in a place where their gestures can be sensed. We discuss the design of our technique and three experiments investigating its use, finding that users can “do that” well (93.2%–99.9%) while accurately (51mm–80mm) and quickly (3.7s) finding “there”

Multidimensional tactons for non-visual information presentation in mobile devices

Tactons are structured vibrotactile messages which can be used for non-visual information presentation when visual displays are limited, unavailable or inappropriate, such as in mobile phones and other mobile devices. Little is yet known about how to design them effectively. Previous studies have investigated the perception of Tactons which encode two dimensions of information using two different vibrotactile parameters (rhythm and roughness) and found recognition rates of around 70. When more dimensions of information are required it may be necessary to extend the parameter-space of these Tactons. Therefore this study investigates recognition rates for Tactons which encode a third dimension of information using spatial location. The results show that identification rate for three-parameter Tactons is just 48, but that this can be increased to 81 by reducing the number of values of one of the parameters. These results will aid designers to select suitable Tactons for use when designing mobile displays