Integration of thin-film ZnO strain sensors into hard disk drives

This work developed a novel application of piezo electric thin-film sensing technology by incorporating ZnO strain sensors into a hard disk drive (HDD) to support the high-bandwidth, nanometer-level positioning required to achieve terabit-per-square-inch data densities. First, ZnO sensors were fabricated directly onto a HDD suspension component, which was a unique and challenging process since the substrate was made of steel. The instrumented suspension was then incorporated into an experimental HDD, along with a miniaturized instrumentation circuit and PZT actuation elements. The sensors demonstrated excellent sensitivity to structural vibration modes that contribute to displacement in the off-track direction. A simple active mode damping controller was implemented on these instrumented PZT-actuated prototypes to demonstrate suppression of high frequency vibration modes.