  The recent development of wearable devices is revolutionizing the way of
human-machine interaction (HMI). Nowadays, an interactive interface that
carries more embedded information is desired to fulfil the increasing demand in
era of Internet of Things. However, present approach normally relies on sensor
arrays for memory expansion, which inevitably brings the concern of wiring
complexity, signal differentiation, power consumption, and miniaturization.
Herein, a one-channel based self-powered HMI interface, which uses the
eigenfrequency of magnetized micropillar (MMP) as identification mechanism, is
reported. When manually vibrated, the inherent recovery of the MMP caused a
damped oscillation that generates current signals because of Faraday's Law of
induction. The time-to-frequency conversion explores the MMP-related
eigenfrequency, which provides a specific solution to allocate diverse commands
in an interference-free behavior even with one electric channel. A cylindrical
cantilever model was built to regulate the MMP eigenfrequencies via precisely
designing the dimensional parameters and material properties. We show that
using one device and two electrodes, high-capacity HMI interface can be
realized when the MMPs with different eigenfrequencies have been integrated.
This study provides the reference value to design the future HMI system
especially for situations that require a more intuitive and intelligent
communication experience with high-memory demand.
