Perceiving Synchrony: Determining Thermal-tactile Simultaneity Windows.

In cutaneous displays in which both tactile and thermal signals are presented, it is important to understand the temporal requirements associated with presenting these signals so that they are perceptually synchronous. Such synchrony is important to provide realistic touch experiences in applications involving object recognition and social touch interactions. In the present experiment the temporal window within which tactile and warm thermal stimuli are perceived to occur at the same time was determined.

Haptic Communication of Language.

In this review, the development of communication systems and devices that convey language tactually is examined, first from an historical perspective focusing on the communities who use the tactile modality to substitute for impairments in vision and/or hearing. Then, the more recent developments in wearable tactile communication systems for conveying text and speech to those without sensory impairments are reviewed. The performance of tactile display technology developed for these user communities is discussed in the context of the proficiency achieved by skilled users of natural methods of tactile communication.

Presenting Surface Features Using a Haptic Ring: A Psychophysical Study on Relocating Vibrotactile Feedback.

In the context of wearable technologies, it is often important for the fingers to be unconstrained so that they can be used to explore the environment. In this paper, we explored the feasibility of presenting vibrotactile cues that represented different textures to one of three locations on the hand and forearm using a wearable device. The first experiment indicated that vibrotactile signals of varying frequency rendered by the tactile display could be encoded by participants in terms of changes along a roughness-smoothness dimension.

Wearable Tactile Display Based on Thermal Expansion of Nichrome Wire.

A wearable tactile display needs to be compact and lightweight, and ideally should be able to present vibration, force, and temperature information to the hand. In many contexts spatially distributed tactile information is needed such as when identifying the shape of objects. In this paper, a multi-element tactile display is described based on the thermal expansion and contraction of nichrome wire.

Shape Localization and Recognition Using a Magnetorheological-Fluid Haptic Display.

Smart materials such as magnetorheological fluids (MRF) offer an interesting technology for use in haptic displays as changes in the magnetic field are rapid, reversible, and controllable. These interfaces have been evaluated in a number of medical and surgical simulators where they can provide cues regarding the viscoelastic properties of tissues. The objective of the present set of experiments was first to determine whether a shape embedded in the MRF could be precisely localized and second whether 10 shapes rendered in a MRF haptic display could be accurately identified.

Multidirectional In Vivo Characterization of Skin Using Wiener Nonlinear Stochastic System Identification Techniques.

A triaxial force-sensitive microrobot was developed to dynamically perturb skin in multiple deformation modes, in vivo. Wiener static nonlinear identification was used to extract the linear dynamics and static nonlinearity of the force-displacement behavior of skin. Stochastic input forces were applied to the volar forearm and thenar eminence of the hand, producing probe tip perturbations in indentation and tangential extension.

Displaying shape haptically using MRF-based device.

Smart materials such as magnetorheological fluids (MRF) offer an interesting medium to present viscoelastic cues in haptic displays as changes in the magnetic field are rapid, reversible and controllable. These interfaces have been evaluated in a number of medical and surgical simulators where they can provide cues regarding the viscoelastic properties of tissues. The present experiment determined whether eight different shapes could be identified reliably with a MRF haptic display and compared the information transfer (IT) associated with this type of display with that achieved by other forms of haptic communication.

Needle-free delivery of macromolecules through the skin using controllable jet injectors.

Introduction: Transdermal delivery of drugs has a number of advantages in comparison to other routes of administration. The mechanical properties of skin, however, impose a barrier to administration and so most compounds are administered using hypodermic needles and syringes. In order to overcome some of the issues associated with the use of needles, a variety of non-needle devices based on jet injection technology has been developed.

Evaluating vibrotactile dimensions for the design of tactons.

Vibrotactile stimuli are defined in terms of their amplitude, frequency, waveform and temporal profile all of which have been varied to create tactons. A number of approaches have been adopted to design tactons including multidimensional scaling, iterative empirical methods and using perceptual processing models. The objective of the present set of experiments was to create sets of tactons based on the properties of the dimensions of vibrotactile stimuli.

Mechanical and psychophysical studies of surface wave propagation during vibrotactile stimulation.

Tactile displays are often used to present spatial cues about the environment, although the optimal configuration of a display used for spatial cuing is not known. The objective of the present set of experiments was to characterize the properties of surface waves induced by vibrotactile stimulation and to determine if the propagation of surface waves was a factor influencing the ability to localize a point of stimulation in a tactile display. Three sites on the body were tested: the palm of the hand, the forearm, and the thigh.

Application of psychophysical techniques to haptic research.

Various psychophysical methods have been used to study human haptic perception, although the selection of a particular method is often based on convention, rather than an analysis of which technique is optimal for the question being addressed. In this review, classical psychophysical techniques used to measure sensory thresholds are described as well as more modern methods such as adaptive procedures and those associated with signal detection theory. Details are provided as to how these techniques should be implemented to measure absolute and difference thresholds and factors that influence subjects' responses are noted.

Tactile sensory system: encoding from the periphery to the cortex.

Specialized mechanoreceptors in the skin respond to mechanical deformation and provide the primary input to the tactile sensory system. Although the morphology of these receptors has been documented, there is still considerable uncertainty as to the relation between cutaneous receptor morphology and the associated physiological responses to stimulation. Labelled-line models of somatosensory processes in which specific mechanoreceptors are associated with particular sensory qualities fail to account for the evidence showing that all types of tactile afferent units respond to a varying extent to most types of natural stimuli.

Tactile communication systems optimizing the display of information.

Tactile communication systems based on vibrotactile signals have been developed as sensory substitution devices for those with visual, auditory, or vestibular impairments and to assist users in spatial orientation and navigation in unfamiliar environments. One of the main challenges in using tactile displays to compensate for sensory loss in other modalities or to overcome the limitations of visual and auditory information overload is in determining what type of information can be presented tactually and which parameters of stimulation can be used to convey these messages effectively. Psychophysical studies of vibrotactile perception provide a framework that assists in determining which stimulus dimensions and ranges of values can be used to create tactile patterns, known as tactons.

Thermal cues and the perception of force.

Two experiments were conducted to examine the effect of temperature on force perception. The objective of the first experiment was to quantify the change in skin temperature of the finger as a function of contact force, in order to characterize how much temperature changes under normal contact conditions. The decrease in temperature ranged from 2.

Vibrotactile pattern recognition on the arm and back.

A series of experiments was conducted to evaluate the effectiveness with which a tactile display mounted on either the forearm or the back can be used to communicate simple instructions and commands. In the first two sets of experiments, participants identified a vibrotactile pattern using a visual template that represented the pattern of activation. For the patterns displayed on the forearm, accuracy depended on the specific set of patterns presented and ranged from 30% to 96% correct for the individual patterns.

Spatial acuity and summation on the hand: the role of thermal cues in material discrimination.

The spatial characteristics of thermal perception were studied in two experiments that examined how thermal stimuli are processed within the hands. A thermal display that simulates cues associated with making contact with different materials was used in these studies. In the first experiment, participants indicated which of two simulated materials that were presented to the index fingertip was cooler.

Modeling the thermal responses of the skin surface during hand-object interactions.

The objective of this research is to analyze and model the decreases in skin temperature when the hand makes contact with an object at room temperature so that thermal feedback can be incorporated into haptic displays. A thermal model is proposed that predicts the thermal responses of the skin and object surface as well as the heat flux exchanged during hand-object interactions. The model was evaluated by comparing the theoretical predictions of temperature changes to those experimentally measured using an infrared thermal measurement system.

Tactile displays: guidance for their design and application.

Objective: This article provides an overview of tactile displays. Its goal is to assist human factors practitioners in deciding when and how to employ the sense of touch for the purpose of information representation. The article also identifies important research needs in this area.

Contribution of thermal cues to material discrimination and localization.

The objective of these two experiments was to determine the role of thermal cues in material discrimination and localization, using materials that spanned a range of thermal properties. In the first experiment, the subjects were required to select the cooler of two materials presented to the index fingers. In the second, the finger that was in contact with a material that was different from that presented to the other two fingers on the same hand had to be identified.

Contribution of tactile feedback from the hand to the perception of force.

A force-matching task was used to study the influence of constraining tactile information from the hand on the perception of forces generated with the index finger flexors, the palmar prehensile grasp and with the elbow flexors. Subjects generated the same reference forces (2-10 N) with each muscle group and matched these using the corresponding muscle group in the other arm. Force perception was studied under normal conditions and when the tactile feedback from the fingertips was constrained through the use of rigid finger splints.

System identification of the human vestibulo-ocular reflex during head-free tracking.

A method was developed to identify the linear, system level dynamics of the horizontal, angular vestibulo-ocular reflex (VOR) as it stabilized vision during head-free tracking of a visual target. Small amplitude, broad spectrum, stochastic torque perturbations were applied to the head while the subject tracked an unpredictable, moving target with active head and eye motions. Stochastic system identification techniques were used to design the torque and target inputs and to conduct the analysis such that the linear dynamics of the VOR, independently of the visual system's influence on eye motions, were determined.

Perceptual constancy and the perceived magnitude of muscle forces.

The present study used a force-matching task to measure how accurately subjects could match a force using different muscle groups. Forces ranging in magnitude from 2 to 10 N were produced and matched by three muscle groups: the elbow flexors, the forearm and hand muscles involved in the palmar prehensile grasp, and the index finger flexors. The ability to match forces was considered in terms of precision, that is, how closely the matching forces approximated the reference force produced on the contralateral side, and accuracy, which is the reproducibility of the matching force estimates.

Dynamics of the human head-neck system in the horizontal plane: joint properties with respect to a static torque.

The vestibular system has often been studied by perturbing the position of the head. This study was conducted to identify the dynamic properties of the head-neck system in response to horizontal plane perturbations. A quasilinear approach was used to quantify the dynamics of the head-neck system at different levels of static torque.