Tactation is the sensation perceived by the sense of touch, and is based on the skin's receptors. Touch is a common medium used by the general population and the sensory impaired. Tactile substitution can be used by the blind or deaf in order to: (a) enhance access to computer graphical user interfaces and (b) enhance mobility in controlled environments.The skin nerves can be stimulated through six types of receptors by mechanical, electrical, or thermal stimuli. Modalities, such as vibration and pressure, can stimulate these receptors. Advances in tactile communication using implementations of the actuating devices have been developed via several new technologies. These technologies include static or vibrating pins, focused ultrasound, electrical stimulation, surface acoustic waves, and other. This paper is a review of the state-of-the-art in the physiological and technological principles, considerations and characteristics, as well as latest implementations of microactuator-based tactile graphic displays. We also review fabrication technologies, in order to demonstrate the potential and limitations in tactile applications.

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The last years a growing body of research has been developed on tactile displays and interfaces, which can give physical form to digital information. In spite of the numerous tactile devices that have been constructed, the development of formal definition for tactile information still remains an open issue. In order for the software to better enhance the tactile information sensation, flow and perception and also drive tactile interfaces we need a formal representation of tactile information. The tactile information ontology proposed in this article analyzes the existing knowledge in tactile information domain, specifies the conceptual structure, and defines the processes that take part in the tactile information flow. Furthermore, the developed ontological representation encodes knowledge into computer understandable form and will allow the sharing and reuse of this knowledge by software tools. The proposed model will be used to identify how tactile displays can improve human-computer interaction, set the principles that are required to design effective user interfaces and assist the development of software for tactile displays. Along with the ontological model, a case study relative to the perception of roughness, generated by a tactile device, has been described.Ontologies have gathered increased attention as they have been recognized to be useful not only in knowledge-based systems but also in the software development process (Devedzic, 2002;Rubin et al., 2007). An ontology defines the basic terms and relations comprising the vocabulary of a topic area in machine-interpretable way as well as the rules for combining terms and relations to define extensions to the vocabulary (Gomez-Perez, 2003). In Devedzic (2002); Gomez-Perez (2003), ontologies are used for communication between systems and people, design and development of knowledge-based systems and interoperable software components, and even classes of objects in object-oriented design. Furthermore, as acknowledged by Noy & McGuiness (2001), the reasons that the ontology development is useful are:(1) to share common understanding of the structure of information among people, (2) to make domain assumptions explicit, (3) to enable reuse of the domain knowledge, (4) to analyze domain knowledge and (5) to separate domain knowledge from operational knowledge. The ontology captures the intrinsic conceptual structure of the domain. In order to build a knowledge representation language based on analysis, we need to associate terms with concepts and relations in the ontology and devise a syntax for encoding knowledge in terms of these concepts and these relations (Chandrasekaran et al., 1999).Tactile information is a complex concept that contains many interrelated elements such as many kinds of stimuli, skin receptors (Iggo, 1984;Johansson, 1978;Macefield, 2005), nerves and brain areas (Bohlhalter et al., 2002;Hlushchuk & Hari, 2006). Their properties and the relations between each element describe the procedure of generation and processing of tactile information an...

This work investigates mechanical limitations of thin film materials on steel foil substrates for flexible electronic applications. A three layer structure consisting of 100μm thick stainless steel foil as the substrate, followed by 1μm thick spin-on-glass passivation layer and 0.3μm thick patterned aluminum interconnect layer on top with varying widths between 10-35μm. A collapsing radius test method was adopted for the bending experiment and an elliptical curve fit was used to facilitate the strain measurement. The failure strain of aluminum interconnect layer was detected by monitoring the continuity of the test circuit during the experiment. The corresponding results reveal that the passivation layer cracked at a tensile strain of 0.46% and delaminated at a compressive strain of 0.68%. The metal interconnect layer ruptured at a tension strain of 1.26% and delaminated from the substrate at a compressive strain of 1.22% due to the delamination of the passivation layer underneath.

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In this paper, the design and simulation of a tactile display that is based on a capacitive micromachined ultrasonic transducer (CMUT) array is presented. The array implements a 'pixel' of the display and is used to focus airborne ultrasound energy on the skin surface. The pressure field generated by the focused ultrasound waves excites the mechanoreceptors under the skin and transmits tactile information. The geometry of the individual transducer and the array are optimized so that the medium presents maximum impedance and the membrane oscillates with maximum deflection. Optimization is achieved using an electrical equivalent circuit model and the Berkeley Simulation Program with Integrated Circuit Emphasis (SPICE) code. Finite element analysis of the CMUT and the CMUT phased array is used to verify the SPICE results. The pressure at focal point is compared with the pressure threshold required for mechanoreceptor excitation in order to verify the feasibility of the design.