471 research outputs found
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
Electroencephalographic Responses to Frictional Stimuli: Measurement Setup and Processing Pipeline
Tactility is a key sense in the human interaction with the environment. The understanding of
tactile perception has become an exciting area in industrial, medical and scienti c research with an
emphasis on the development of new haptic technologies. Surprisingly, the quanti cation of tactile
perception has, compared to other senses, only recently become a eld of scienti c investigation.
The overall goal of this emerging scienti c discipline is an understanding of the causal chain
from the contact of the skin with materials to the brain dynamics representing recognition of
and emotional reaction to the materials. Each link in this chain depends on individual and
environmental factors ranging from the in uence of humidity on contact formation to the role of
attention for the perception of touch.
This thesis reports on the research of neural correlates to the frictional stimulation of the human
ngertip. Event-related electroencephalographic potentials (ERPs) upon the change in ngertip
friction are measured and studied, when pins of a programmable Braille-display were brought into
skin contact. In order to contribute to the understanding of the causal chain mentioned above,
this work combines two research areas which are usually not connected to each other, namely
tribology and neuroscience. The goal of the study is to evaluate contributions of friction to the
process of haptic perception. Key contributions of this thesis are:
1) Development of a setup to simultaneously record physical forces and ERPs upon tactile
stimulation.
2) Implementation of a dedicated signal processing pipeline for the statistical analysis of ERP
-amplitudes, -latencies and -instantaneous phases.
3) Interpretation of skin friction data and extraction of neural correlates with respect to varying
friction intensities.
The tactile stimulation of the ngertip upon raising and lowering of di erent lines of Braille-pins
(one, three and ve) caused pronounced N50 and P100 components in the event-related ERPsequences,
which is in line with the current literature. Friction between the ngertip and the
Braille-system exhibited a characteristic temporal development which is attributed to viscoelastic
skin relaxation. Although the force stimuli varied by a factor of two between the di erent Braillepatterns,
no signi cant di erences were observed between the amplitudes and latencies of ERPs
after standard across-trial averaging. Thus, for the rst time a phase measure for estimating singletrial
interactions of somatosensory potentials is proposed. Results show that instantaneous phase
coherency is evoked by friction, and that higher friction induces stronger and more time-localized
phase coherencyDie TaktilitÀt ist ein zentraler Sinn in der Interaktion mit unserer Umwelt. Das Bestreben,
fundierte Erkenntnisse hinsichtlich der taktilenWahrnehmung zu gewinnen erhÀlt groÿen Zuspruch
in der industriellen, medizinischen und wissenschaftlichen Forschung, meist mit einem Fokus auf
der Entwicklung von haptischen Technologien. Erstaunlicherweise ist jedoch die wissenschaftliche
Quanti zierung der taktilen Wahrnehmung, verglichen mit anderen SinnesmodalitÀten, erst seit
kurzem ein sich entwickelnder Forschungsbereich. Fokus dieser Disziplin ist es, die kognitive und
emotionale Reaktion nach physischem Kontakt mit Materialien zu beschreiben, und die kausale
Wirkungskette von der BerĂŒhrung bis zur Reaktion zu verstehen. Dabei unterliegen die einzelnen
Faktoren dieser Kette sowohl individuellen als auch externen Ein ĂŒssen, welche von der Luftfeuchtigkeit
wĂ€hrend des Kontaktes bis hin zur Rolle der Aufmerksamkeit fĂŒr die Wahrnehmung
reichen.
Die vorliegende Arbeit beschÀftigt sich mit der Untersuchung von neuronalen Korrelaten nach
Reibungsstimulation des menschlichen Fingers. Dazu wurden ReibungsÀnderungen, welche durch
den Kontakt der menschlichen Fingerspitze mit schaltbaren Stiften eines Braille-Display erzeugt
wurden, untersucht und die entsprechenden neuronalen Korrelate aufgezeichnet. Um zu dem Verst
Ă€ndnis der oben erwĂ€hnten Wirkungskette beizutragen, werden AnsĂ€tze aus zwei fĂŒr gewöhnlich
nicht zusammenhÀngenden Forschungsbereichen, nÀmlich der Tribologie und der Neurowissenschaft,
kombiniert. Folgende BeitrÀge sind Hauptbestandteile dieser Arbeit:
1) Realisierung einer Messumgebung zur simultanen Ableitung von KrÀften und ereigniskorrelierten
Potentialen nach taktiler Stimulation der Fingerspitze.
2) Aufbau einer speziellen Signalverarbeitungskette zur statistischen Analyse von stimulationsabh
Ă€ngigen EEG -Amplituden, -Latenzen und -instantanen Phasen.
3) Interpretation der erhobenen Reibungsdaten und Extraktion neuronaler Korrelate hinsichtlich
variierender StimulationsintensitÀten.
Unsere Resultate zeigen, dass die taktile Stimulation der Fingerspitze nach Anheben und Senken
von Braille-Stiften zu signi kanten N50 und P100 Komponenten in den ereigniskorrelierten Potentialen
fĂŒhrt, im Einklang mit der aktuellen Literatur. Die Reibung zwischen der Fingerspitze
und dem Braille-System zeigte einen charakteristischen Signalverlauf, welcher auf viskoelastische
Hautrelaxation zurĂŒckzufĂŒhren ist. Trotz der um einen Faktor zwei verschiedenen Intensit
Ă€tsunterschiede zwischen den Stimulationsmustern zeigten sich keine signi kanten Unterschiede
zwischen den einfach gemittelten Amplituden der evozierten Potentialen. Erstmalig wurde ein
Phasen-MaĂż zur Identi zierung von Unterschieden zwischen somatosensorischen "single-trial" Interaktionen
angewandt. Diese Phasenanalyse zeigte, im Gegensatz zur Amplituden- und Latenzanalyse,
deutlichere und signi kantere Unterschiede zwischen den Stimulationsparadigmen. Es
wird gefolgert, dass KohÀrenz zwischen den Momentanphasen durch Reibungsereignisse herbeigef
ĂŒhrt wird und dass durch stĂ€rkere Reibung diese KohĂ€renz, im zeitlichen Verlauf, stĂ€rker und
lokalisierter wird
Electrotactile feedback applications for hand and arm interactions: A systematic review, meta-analysis, and future directions
Haptic feedback is critical in a broad range of
human-machine/computer-interaction applications. However, the high cost and low
portability/wearability of haptic devices remain unresolved issues, severely
limiting the adoption of this otherwise promising technology. Electrotactile
interfaces have the advantage of being more portable and wearable due to their
reduced actuators' size, as well as their lower power consumption and
manufacturing cost. The applications of electrotactile feedback have been
explored in human-computer interaction and human-machine-interaction for
facilitating hand-based interactions in applications such as prosthetics,
virtual reality, robotic teleoperation, surface haptics, portable devices, and
rehabilitation. This paper presents a technological overview of electrotactile
feedback, as well a systematic review and meta-analysis of its applications for
hand-based interactions. We discuss the different electrotactile systems
according to the type of application. We also discuss over a quantitative
congregation of the findings, to offer a high-level overview into the
state-of-art and suggest future directions. Electrotactile feedback systems
showed increased portability/wearability, and they were successful in rendering
and/or augmenting most tactile sensations, eliciting perceptual processes, and
improving performance in many scenarios. However, knowledge gaps (e.g.,
embodiment), technical (e.g., recurrent calibration, electrodes' durability)
and methodological (e.g., sample size) drawbacks were detected, which should be
addressed in future studies.Comment: 18 pages, 1 table, 8 figures, under review in Transactions on
Haptics. This work has been submitted to the IEEE for possible publication.
Copyright may be transferred without notice, after which this version may no
longer be accessible.Upon acceptance of the article by IEEE, the preprint
article will be replaced with the accepted versio
Oral Somatosensory Awareness
Oral somatosensory awareness refers to the somatic sensations arising within the mouth, and to the information these sensations provide about the state and structure of the mouth itself, and objects in the mouth. Because the oral tissues have a strong somatosensory innervation, they are the locus of some of our most intense and vivid bodily experiences. The salient pain of toothache, or the habit of running one's tongue over one's teeth when someone mentions "dentist", provide two very different indications of the power of oral somatosensory awareness in human experience and behaviour. This paper aims to review the origins and structure of oral somatosensory awareness, focussing on quantitative, mechanistic studies in humans. We first extend a model of levels of bodily awareness to the specific case of the mouth. We then briefly summarise the sensory innervation of oral tissues, and their projections in the brain. We next describe how these peripheral inputs give rise to perceptions of objects in the mouth, such as foods, liquids and oral devices, and also of the mouth tissues themselves. Finally, we consider the concept of a conscious mouth image, and the somatosensory basis of "mouth feel". The theoretical framework outlined in this paper is intended to facilitate scientific studies of this important site of human experience
Touching on elements for a non-invasive sensory feedback system for use in a prosthetic hand
Hand amputation results in the loss of motor and sensory functions, impacting activities of daily life and quality of life. Commercially available prosthetic hands restore the motor function but lack sensory feedback, which is crucial to receive information about the prosthesis state in real-time when interacting with the external environment. As a supplement to the missing sensory feedback, the amputee needs to rely on visual and audio cues to operate the prosthetic hand, which can be mentally demanding. This thesis revolves around finding potential solutions to contribute to an intuitive non-invasive sensory feedback system that could be cognitively less burdensome and enhance the sense of embodiment (the feeling that an artificial limb belongs to oneâs own body), increasing acceptance of wearing a prosthesis.A sensory feedback system contains sensors to detect signals applied to the prosthetics. The signals are encoded via signal processing to resemble the detected sensation delivered by actuators on the skin. There is a challenge in implementing commercial sensors in a prosthetic finger. Due to the prosthetic fingerâs curvature and the fact that some prosthetic hands use a covering rubber glove, the sensor response would be inaccurate. This thesis shows that a pneumatic touch sensor integrated into a rubber glove eliminates these errors. This sensor provides a consistent reading independent of the incident angle of stimulus, has a sensitivity of 0.82 kPa/N, a hysteresis error of 2.39±0.17%, and a linearity error of 2.95±0.40%.For intuitive tactile stimulation, it has been suggested that the feedback stimulus should be modality-matched with the intention to provide a sensation that can be easily associated with the real touch on the prosthetic hand, e.g., pressure on the prosthetic finger should provide pressure on the residual limb. A stimulus should also be spatially matched (e.g., position, size, and shape). Electrotactile stimulation has the ability to provide various sensations due to it having several adjustable parameters. Therefore, this type of stimulus is a good candidate for discrimination of textures. A microphone can detect texture-elicited vibrations to be processed, and by varying, e.g., the median frequency of the electrical stimulation, the signal can be presented on the skin. Participants in a study using electrotactile feedback showed a median accuracy of 85% in differentiating between four textures.During active exploration, electrotactile and vibrotactile feedback provide spatially matched modality stimulations, providing continuous feedback and providing a displaced sensation or a sensation dispatched on a larger area. Evaluating commonly used stimulation modalities using the Rubber Hand Illusion, modalities which resemble the intended sensation provide a more vivid illusion of ownership for the rubber hand.For a potentially more intuitive sensory feedback, the stimulation can be somatotopically matched, where the stimulus is experienced as being applied on a site corresponding to their missing hand. This is possible for amputees who experience referred sensation on their residual stump. However, not all amputees experience referred sensations. Nonetheless, after a structured training period, it is possible to learn to associate touch with specific fingers, and the effect persisted after two weeks. This effect was evaluated on participants with intact limbs, so it remains to evaluate this effect for amputees.In conclusion, this thesis proposes suggestions on sensory feedback systems that could be helpful in future prosthetic hands to (1) reduce their complexity and (2) enhance the sense of body ownership to enhance the overall sense of embodiment as an addition to an intuitive control system
The temporal pattern of impulses in primary afferents analogously encodes touch and hearing information
An open question in neuroscience is the contribution of temporal relations between individual impulses in primary afferents in conveying sensory information. We investigated this question in touch and hearing, while looking for any shared coding scheme. In both systems, we artificially induced temporally diverse afferent impulse trains and probed the evoked perceptions in human subjects using psychophysical techniques.
First, we investigated whether the temporal structure of a fixed number of impulses conveys information about the magnitude of tactile intensity. We found that clustering the impulses into periodic bursts elicited graded increases of intensity as a function of burst impulse count, even though fewer afferents were recruited throughout the longer bursts.
The interval between successive bursts of peripheral neural activity (the burst-gap) has been demonstrated in our lab to be the most prominent temporal feature for coding skin vibration frequency, as opposed to either spike rate or periodicity. Given the similarities between tactile and auditory systems, second, we explored the auditory system for an equivalent neural coding strategy. By using brief acoustic pulses, we showed that the burst-gap is a shared temporal code for pitch perception between the modalities.
Following this evidence of parallels in temporal frequency processing, we next assessed the perceptual frequency equivalence between the two modalities using auditory and tactile pulse stimuli of simple and complex temporal features in cross-sensory frequency discrimination experiments. Identical temporal stimulation patterns in tactile and auditory afferents produced equivalent perceived frequencies, suggesting an analogous temporal frequency computation mechanism.
The new insights into encoding tactile intensity through clustering of fixed charge electric pulses into bursts suggest a novel approach to convey varying contact forces to neural interface users, requiring no modulation of either stimulation current or base pulse frequency. Increasing control of the temporal patterning of pulses in cochlear implant users might improve pitch perception and speech comprehension. The perceptual correspondence between touch and hearing not only suggests the possibility of establishing cross-modal comparison standards for robust psychophysical investigations, but also supports the plausibility of cross-sensory substitution devices
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