Conventional tactile sensors can only detect simple physical values such as pressure, but can hardly measure multi-directional movements in touch with the surface of objects.
We propose a soft tactile sensor using an Ionic Polymer-Metal Composite (IPMC or known as ICPF). IPMC is excellent in softness, durability, easy molding, and so on. Many applications have been developed using as IPMC actuators. IPMC can also utilized as a sensor, because a voltage on the both ends of the film changes by adding mechanical stimuli and bending the film. It is found experimentally that IPMC has the characteristics as a speed sensor because the output voltages were in proportion to the velocities of the end of films by making vibrational motions.
A tactile speed sensor that can measure the velocity vectors in 3-dimenstional movements was developed. The sensor has centroclinal structure made of silicone gel capsule, and four IPMC sensor modules were combined with the capsule inside in cross shape. The silicon gel capsule also seal in water, which is necessary for IPMC devices. The output voltages of each sensor were calibrated into the same maximum outputs because IPMC sensors have response variation. The amount of the velocity was estimated by calculating four outputs of each sensor modules. The direction of the movement can also be estimated by them only when the amount of the velocity exceeds the sufficient level. Experimental results show the sensor could estimate the velocity vector in real-time.
A tactile feel display device for virtual reality was developed using Nafion-Platinum composite type EAP actuator (known as IPMC or ICPF). Conventional tactile displays can hardly express tactile human feeling of the fine touch of the surface of a cloth, because their mechanisms cannot excite minute distributed stimuli on human skin. We propose a new ciliary device using ICPF actuators. The ICPF has sufficient softness, utilizing the passive material property, that complex control is not required. The low drive voltage is safe enough for the touch of fingers. Its simple operation mechanism allows miniaturization for practical equipments. The developed device was designed with a number of cilia consisting of ICPF actuators, where a cilium is 2 mm wide and 5 mm long. An ICPF membrane is cut into pectination, and only the cilium part is plated and has a function of an actuator. An inclined configuration of the cilia produces variety of stimuli to human skin controlling frequencies. We tried to display both pressure and vibration at the same time using modulated low and high frequencies. The result clearly shows that over 80% of the subjects sensed some special tactile feeling. A comparison with real material samples shows that this display can present a subtle distinction of tactile feeling of cloth, especially like a towel and denim.