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Ultrasound haptic
Tactile actuator presents “Tactile feeling” which is a sensation produced in our skin when we touch or rub something. Ultrasound has been suggested as a one of actuators to evoke tactile sensation by concentrating high frequency waves on skin surface.
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Our Aim
The purpose of our research is to create biomimetic tactile feelings with ultrasound as a kind of sensation which can be recorded, reproduced, and transmitted. By arranging these actuators as 2-D array, complex texture can be reproduced with high resolution. This technology can be applied to the development of various haptic sensors and haptic stimulus devices.
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Topics
- Optimization of ultrasonic stimulation for complex texture sensation
- Micro multi-array ultrasound transducer and control system
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Recent Papers
Analysis of Temporal Firing Patterns of Primary Afferent C-Fibers for Different Sensations in Mice
(Kyeongwon Cho et. al., International Journal of Precision Engineering and Manufacturing, 2017)
The temporal spike train pattern generated in healthy subject’s nerve by various types of somatosensation could provide key information to closely mimic natural sensations using electrical stimulation. However, the temporal firing patterns of peripheral sensory fibers have not been well understood yet. To interpret somatosensory spike trains, we performed ex vivo single fiber recordings from the saphenous nerve in isolated skin-nerve preparations from mice. Some mechanically sensitive primary afferent C-fibers could also be activated by hot, cold, and itching stimuli, and we observed stimulus-specific firing patterns. These temporal patterns of the C-fibers for chemical stimuli were analyzed using a computational model based on quadruplets of spikes, which we classified into three groups of responses, i.e., capsaicin (hot), allyl-isothiocyanate (cold), and α-methyl-serotonin (itching). Each group of responses to the chemical stimuli was different from that evoked by mechanical stimuli. Therefore, these findings indicate that nontactile somatosensation can be decoded and used as input to a computerized system. Our quadruplet approach to the temporal patterns of spike trains contributes valuable insight to the identification of temporal profiles of other biological conditions.
Analysis of Nociceptive Information Encoded in the Temporal Discharge Patterns of Cutaneous C-Fibers
(Kyeongwon Cho et. al., Frontiers in computational neuroscience, 2016)
The generation of pain signals from primary afferent neurons is explained by a labeled-line code. However, this notion cannot apply in a simple way to cutaneous C-fibers, which carry signals from a variety of receptors that respond to various stimuli including agonist chemicals. To represent the discharge patterns of C-fibers according to different agonist chemicals, we have developed a quantitative approach using three consecutive spikes. By using this method, the generation of pain in response to chemical stimuli is shown to be dependent on the temporal aspect of the spike trains. Furthermore, under pathological conditions, gamma-aminobutyric acid resulted in pain behavior without change of spike number but with an altered discharge pattern. Our results suggest that information about the agonist chemicals may been coded in specific temporal patterns of signals in C-fibers, and nociceptive sensation may be influenced by the extent of temporal summation originating from the temporal patterns.
Analysis of the relationships between tactile threshold and displacement properties by focused ultrasound stimulation
(Jeongbong Choi et. al., in preparation)
To optimize focused ultrasound stimulation as a potential tactile display, there have been various studies to investigate the relationships between tactile sensation and ultrasonic parameters such as pulse duration and pulse frequency. In this study, the relationships of a tactile sensation threshold with the properties of displacement were investigated by designing an experimental apparatus consisting of a polydimethylsiloxane (PDMS) interface between skin and an ultrasound probe. Tactile threshold pressure was measured from subjects with various pulse frequencies and pulse durations. When the displacement was measured while focused ultrasound was applied with pulse duration and a tactile threshold pressure level was obtained from each subject’s tactile response, the PDMS displacement exhibited a linear increase as the length of the stimulus pulse increased, while the logarithm scale of displacement change decreased. Therefore, a tactile threshold can be determined based on the combination of the amount of displacement and the displacement change rate. That is, tactile sensation could be evoked with a faster displacement change rate in the case of a small displacement or vice versa. In conclusion, the properties of displacement need to be considered with the other ultrasonic parameters in focused ultrasound tactile stimulation studies.