A stretchable pressure sensor can provide highly sensitive and strain-unperturbed measurement to pressures on deformed skins.

Realistic haptic feedback is needed to provide information to users of numerous technologies, such as virtual reality, mobile devices, and robotics. For a device to convey realistic haptic feedback, two touch sensations must be present: tactile feedback and kinesthetic feedback. Although many devices today convey tactile feedback through vibrations, most neglect to incorporate kinesthetic feedback. To address this issue, this study investigates a haptic device with the aim of conveying both kinesthetic and vibrotactile information to users. A prototype based on electrorheological fluids was designed and fabricated. By controlling the electrorheological fluid flow via applied electric fields, the device can generate a range of haptic sensations. The design centered on an elastic membrane that acts as the actuator’s contact surface. Moreover, the control electronics and structural components were integrated into a compact printed circuit board, resulting in a slim device suitable for mobile applications. The device was tested using a dynamic mechanical analyzer to evaluate its performance. The device design was supported with mathematical modeling and was in agreement with experimental results. According to the just-noticeable difference analysis, this range is sufficient to transmit distinct kinesthetic and vibrotactile sensations to users, indicating that the electrorheological fluid–based actuator is capable of conveying haptic feedback.

Robust haptic devices that can convey the entire spectrum of human touch perception are necessary to afford realistic haptic experiences. For vivid and immersive interaction, a combination of both tactile and kinesthetic information must be presented to users. While vibrotactile feedback has become ubiquitous in today's handheld devices, traditional kinesthetic actuators present significant challenges to miniaturization. Moreover, only limited success has been achieved in developing haptic actuators capable of conveying both tactile and kinesthetic sensations for small consumer electronics. Therefore, this study presents a compact actuator based on electrorheological (ER) fluid for generating a wide range of concurrent kinesthetic and tactile feedback. The design focus for the proposed actuator is to activate multiple operating modes of ER fluid to maximize the force generated by the actuator within a given small size constraint. To this end, the design incorporated two ground electrodes (a stationary ring electrode and a movable electrode attached to a spring element) for tuning the fluid's yield stress in both flow and squeeze modes. After fabricating a prototype actuator, testing was performed with a dynamic mechanical analyzer (DMA) and an accelerometer to evaluate its ability to produce a wide range of kinesthetic feedback, as well as distinct vibrotactile feedback up to the limit of human perception. The results of kinesthetic testing indicate that the actuator can generate large forces (6.2 N maximum at 4 kV) at rates greater than the just-noticeable difference, indicating that the actuator can convey a wide range of kinesthetic sensations. Tactile evaluation using DMA and the processed acceleration response demonstrated that the actuator can generate both low and high frequency (up to 300 Hz) vibrotactile sensations at perceivably high intensity.

We present a miniature haptic module based on electrorheological fluid, designed for conveying combined stiffness and vibrotactile sensations at a small scale. Haptic feedback is produced through electrorheological fluid’s controllable resistive force and varies with the actuator’s deformation. To demonstrate the proposed actuator’s feedback in realistic applications, a method for measuring the actuator’s deformation must be implemented for active control. To this end, in this study, we incorporate a sensor design based on a bend-sensitive resistive film to the ER haptic actuator. The combined actuator and sensor module was tested for its ability to simultaneously actuate and sense the actuator’s state under indentation. The results show that the bend sensor can accurately track the actuator’s displacement over its stroke. Thus, the proposed sensor may enable control of the output resistive force according to displacement, which may lead to more informed and engaging combined kinesthetic and tactile feedback.

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