Using a smart polymeric material, we design a transparent and stretchable empathetic haptic skin cushion that secretly allows a target device to understand users’ emotions. The skin comprises highly transparent and stretchable conducting hydrogels and a plasticized nonionic polyvinyl chloride (PNIPVC) whose dielectric, electrical, optical, and mechanical properties are adjusted by the type, ratio, and concentration of the dual-plasticizers. Hydrogels adhere strongly to the upper and lower surfaces of the PNIPVC via covalent bonding to form durable, reliable, and sensitive empathetic skin. The skin exhibits excellent transparency and stretchability with low mechanical hysteresis. In addition, the skin senses the capacitance or resistance of the PNIPVC by varying its operating frequency, which enables the perception of various external pressures for detecting emotional touches (tapping, patting, stretching, pinching, and twisting). Thus, the skisn cushion can be used as a new tactile emotional interface system for future emotion-interactive shape-deformable materials and devices.

In this paper, we propose a bidirectional soft haptic I/O module that not only senses the haptic force but also generates a mechanical vibrotactile sensation. Under external pressure, the distance between the moving plate and lower electrode layer decreases, and the bpPVC gel gets compressed. These two motions make the capacitance of the proposed module change. Moreover, the application of external electric field creates an electrostatic force between the upper and lower electrode layers and generates the electric-field-induced deformation of the bpPVC gel simultaneously. As soon as the external electric field disappears, the proposed module regains its original shape through the elastic restoring forces of the bpPVC gel and planar springs. Therefore, the applied AC voltage makes the proposed module vibrate. The dielectric and mechanical properties of the bpPVC gel are measured to investigate the optimal weight ratio of the PVC and plasticizers. Experiments are conducted to measure the haptic sensing and actuating performance of the proposed method. The capacitance of the proposed haptic I/O module increases from 17.4 pF to 54.8 pF when the external pressure varied from 0 kPa to 100 kPa. On the other hand, the haptic output of the proposed I/O module is observed as 0.81 g (g = 9.8 m/s2) at 100 Hz. The results clearly indicate that the proposed haptic I/O module not only senses the static and dynamic pressure but also controls the amplitude of vibrotactile sensation. Owing to its mechanically soft structure, we expect that the proposed haptic I/O module has the potential to be applied or attached to various flexible/soft devices or the human body.

This study presents a transparent and soft haptic actuator based on an electroactive polymer designed to create abundant haptic sensations in flexible/deformable next-generation devices and to convey them to users. The haptic sensations are created in the form of vibrations and vary depending on the amplitude and frequency of the vibrations. The haptic actuator consists of a transparent and soft dielectric layer and two transparent and soft ionic conductive layers. The dielectric layer is sandwiched between the two ionic conductive layers, and is compressed in the thickness direction when an electric field is applied to the two ionic conductive layers. When the applied electric field is removed, the proposed haptic actuators are rapidly restored to their initial configuration. Owing to this effect, the actuator can easily create vibrations that are sufficiently strong for human perception. In this study, three different dielectric elastomers (silicone rubber, poly urethane, and acrylic polymer) are used for the dielectric layer. Experiments are conducted to investigate the haptic performance of the proposed soft vibrotactile actuators using an accelerometer. In the case of the silicone rubber-based actuator, the measured acceleration at the resonant frequency (80 Hz) is 1.408 g (g = 9.8 m/s2 ) and the response time is approximately 2.8 ms. Furthermore, the perceived intensity of the stimuli generated by the proposed actuator is verified by perceptual experiments. The results indicate that the proposed actuator can selectively stimulate human mechanoreceptors with sufficient perceptual strength.

In this paper, we propose a tiny haptic knob that creates torque feedback in consumer electronic devices. To develop the proposed haptic knob, we use a magnetorheological (MR) fluid. When an input current is applied to a solenoid coil, a magnetic field causes a change in the MR fluid’s viscosity. This change allows the proposed haptic knob to generate a resistive torque. We optimize the structure of the haptic knob, in which two operating modes of MR fluids contribute to the actuation simultaneously. We conduct magnetic path simulation and resistive torque simulation using the finite element method and perform experiments to measure the resistive torque and its torque rate according to the rotational speed and applied current. The results show that the proposed haptic knob generates sufficient torque feedback to stimulate users and creates a variety of haptic sensations.

In mobile devices, the screen size limits conveyance of immersive experiences; haptic feedback coupled with visual feedback is expected to have a better effect to maximize the level of immersion. Therefore, this paper presents a miniature tunable haptic stylus based on magnetorheological (MR) fluids to provide kinesthetic information to users. The designed stylus has a force generation, force transmission, and housing part; moreover, in the stylus, all three operating modes of MR fluids contribute to the haptic actuation to produce a wide range of resistive force generated by MR fluids in a limited size, thereby providing a variety of pressing sensations to users. A universal testing machine was constructed to evaluate haptic performance of the proposed haptic stylus, whose resistive force was measured with the constructed setup as a function of pressed depth and input current, and by varying the pressed depth and pressing speed. Under maximum input voltage, the stylus generates a wide range of resistive force from 2.33 N to 27.47 N, whereas under maximum pressed depth it varied from 1.08 N to 27.47 N with a corresponding change in voltage input from 0 V to 3.3 V. Therefore, the proposed haptic stylus can create varied haptic sensations.

A vibrotactile interface is an actuator device to convey haptic information intuitively from electronics to users. For the next‐generation of user‐friendly interface applications, the vibrotactile actuator is required to be vibration intensity/frequency controllable, mechanically stable, transparent, and have large scalability. Previously, although these requirements are satisfied via several approaches using a random network film of Ag wires or a mixture with conductive polymers, the random‐network‐based materials only have limited control on material density and uniformity, which in turn hinders precise control over vibration intensity and device transparency. Here, a new approach to assemble large‐scale Ag microwire arrays is demonstrated by involving an evaporative assembly method and is presented to overcome the current limitations. In particular, the 1D wavy structure derived from fractal designs promotes vibration intensity and cycling due to greater areal coverage and improved mechanical stability. Furthermore, by taking advantage of the precisely aligned microwires array, tunable multimode vibration frequencies are obtained by generating two different voltage frequencies. The large‐scale wavy Ag microwire array with precise spatial controllability will be directly adaptable as a user‐friendly interface in electronic applications like wearable devices, computer interfaces, and flexible mobile phones.

Dong-Soo Choi, Tae-Heon Yang, Won-Chul Bang, and Sang-Youn Kim

Measuring a distance through an ultrasonic sensor and creating haptic alert information by a vibrotactile actuator are two major functions in an electronic aid for a visually impaired person. It is quite challenging to combine and to efficiently execute these two functions with a single module. Thus, this study presents a new structure that measures the distance and generates haptic information with only one module. The design focus of the proposed module is to maximize its vibrotactile amplitude and to minimize its measured distance error. In order to evaluate the performance of the proposed module, a test setup was constructed. Using the setup, the vibrotactile strength of the proposed module was investigated according to the input frequency, and then the distance between the proposed module and a target object was measured. The results show that the proposed module effectively produces haptic information while measuring the distance well between the module and a target object.