The Application of Micro-Vibratory Phenomena of a Shape-Memory Alloy Wire to a Novel Vibrator

The widespread use of smartphones and smart wearable devices has created a great demand for vibrators with complex vibration patterns driven by simple circuits. In our previous studies, we observed that a filiform shape-memory alloy (SMA) wire will shrink and then return to its initial length, perfectly synchronizing with a given pulse current. Here, we developed a novel vibrator whose structure allows the micro-vibrations of an SMA wire to be amplified up to a recognizable level without directly touching the wire. The vibrator has the advantage of independently controlling its magnitude and frequency together with a simple driving circuit since it is directly driven by a frequency-modulated pulse current with a controlled duty ratio. We measured the power consumption and the acceleration generated by the vibrator. The results showed that the vibrator consumed only 4–77 milliwatts of power with a quick vibration response within 5 milliseconds, and the acceleration increased significantly in a duty ratio range of around 1%. Furthermore, user evaluations demonstrated that differences in the magnitude and frequency of the generated vibrations were sufficiently recognized when the vibrator was driven by different duty ratios and frequencies, and the vibrator provided various tactile and haptic sensations to users.