We experience a sense of adhesion when touching a lotion or adhesive tape with a finger and attempting to pull it off. This sense of adhesion is considered an important element of tactile sensation. However, previous methods for presenting this sensation have been limited, and most require relatively large devices. This study proposes a compact method for presenting a sense of adhesion using an electro-tactile display. The electrotactile display can be made wearable, and it allows flexible control over stimulation timing and area. We propose a method for evoking a sense of adhesion by delivering cutaneous electrical stimulation at the timing when a pulling force is generated between the finger and the adhesive object. Additionally, we investigated a method for reproducing changes in the contact area. Experimental results showed that electrical stimulation successfully induced a sense of adhesion when the finger was lifted from the adhesive surface. The results also suggest that stimulation timing contributes more to the perception of adhesion than changes in the stimulation area.
There are individual differences in human tactile sensation, but it is not clear what causes these differences. One possible cause is the varying mechanical properties of the skin. To unravel this, we focused on the skin-propagated vibration characteristics and vibrotactile sensitivity. First, we measured the skin-propagated vibration of the fingertip for 28 participants and then conducted a cluster analysis to determine how the transfer function of the skin vibration differs among participants, estimating mechanical parameters based on the mechanical model. The results indicated that the transfer functions could be grouped according to the magnitude of the high-frequency gain. Subsequently, the detection thresholds for the 200 and 450 Hz vibrotactile stimulation were measured. The correlation analysis between the gain and the detection threshold showed a statistically significant correlation at 450 Hz. The results suggest that individual differences in human perception are influenced by the mechanical differences in the skin as well as the cognitive processing.
Thermal grill illusion (TGI) is a phenomenon involving a painful or burning sensation that is perceived when warm and cold stimuli are simultaneously placed on the skin. We proposed that the TGI can be generated by directly activating transient receptor potential channels, which contribute to temperature perception, with chemical substances such as capsaicin and menthol. This method enables the energy-saving and compact presentation of pain sensations. We examined the reactions of the study subjects to each chemical and then applied two chemicals to the same or adjacent parts of the skin to verify the generation of the TGI (n = 10, recruited from lab members). The results suggest that the application of capsaicin and menthol next to each other generates the TGI.
The stability and fidelity of haptic simulation systems have been studied for a safer and more faithful haptic interaction with virtual environments. The theoretical analysis, which use a second-order model for the actuator does not match well with the experimental results at high sampling rates. In this work, we propose more accurate models and analyze the uncoupled stability and fidelity for a system actuated by a permanent magnet DC motor and its voltage driver when implementing a linear viscoelastic environment. Through theoretical work and experiments, we show that the stability and fidelity of the system are more accurately represented when a high-order dynamic model is used for the motor and its driver.
This paper proposes a pulley-based haptic simulator device as training tool for ureteroscopy allowing for continuous insertion into a virtual ureter. The device motor provides a resistive feedback force to familiarize users with the forces experienced during surgery. We conducted a preliminary evaluation study with 7 subjects to compare subject performance using the system with visual and visuo-haptic feedback. Results support the utility of the device in terms of range forces rendered to the user and accurate following of the ureter profile. The addition of haptic feedback caused the subjects to perform the task more slowly. Future studies will evaluate if haptic feedback leads to enhanced skill development long-term with extended practice.
