Haptic displays have been developed to provide operators with rich tactile information using simple structures. In this study, a three-axis tactile actuator capable of thermal display was developed to deliver tactile senses more realistically and intuitively. The proposed haptic display uses pneumatic pressure to provide shear and normal tactile pressure through an inflation of the balloons inherent in the device. The device provides a lateral displacement of ±1.5 mm for shear haptic feedback and a vertical inflation of the balloon of up to 3.7 mm for normal haptic feedback. It is designed to deliver thermal feedback to the operator through the attachment of a heater to the finger stage of the device, in addition to mechanical haptic feedback. A custom-designed control module is employed to generate appropriate haptic feedback by computing signals from sensors or control computers. This control module has a manual gain control function to compensate for the force exerted on the device by the user’s fingers. Experimental results showed that it could improve the positional accuracy and linearity of the device and minimize hysteresis phenomena. The temperature of the device could be controlled by a pulse-width modulation signal from room temperature to 90 °C. Psychophysical experiments show that cognitive accuracy is affected by gain, and temperature is not significantly affected.

The gasochromism of WO₃, wherein the color of the material changes according to the reaction of gas, can immediately allow for the determination of the presence of hydrogen by the naked eye. We have also developed a hybrid hydrogen sensor for WO₃, a metal oxide, that can simultaneously utilize its gasochromic response and resistance to hydrogen. Because the proposed sensor has a transparent electrode on a glass substrate, it is a structure that can not only reveal the change in resistance but also more clearly illustrate the gasochromic response. A hybrid sensing demonstration in a hydrogen leak environment was successfully performed to verify a sensor that was capable of utilizing the resistive and gasochromic response of WO₃.

In this paper, we propose a skin attachable piezoelectric energy harvester which was implemented by using magnetic alignment of cobalt (Co)-doped zinc oxide nanorods (ZnO NRs) to enhance the piezoelectric effect. Co-doped ZnO NRs with ferromagnetic property can be easily obtained by hydrothermal process, and their uni-directional alignment can be obtained by applying external magnetic field. In addition, double layers of platinum (Pt) and graphene were deposited on the surface as a flexible and stretchable electrode with high electric conductivity. The maximum open-circuit voltage of 17.4 Vp-p and short-circuit current of 0.26 μA was obtained at 4 Hz folding/unfolding operations.