Both piezoresistive and piezoelectric materials are commonly used to detect strain caused by structural vibrations
in macro-scale structures. With the increasing complexity and miniaturization of modern mechanical systems
such as hard disk drive suspensions, it is imperative to explore the performance of these strain sensors when their
dimensions must shrink along with those of the host structures. The miniaturized strain sensors must remain as
small as possible so as to minimum their effect on structure dynamics, yet still have acceptable sensing resolution.
The performances of two types of novel micro-scale strain gage for installation on stainless steel parts are
compared in this paper. Micro-fabrication processes have been developed to build polycrystalline silicon piezoresistive
strain sensors on a silicon substrate, which are later bonded to a steel substrate for testing. Piezoresistor
geometries are optimized to effectively increase the gage factor of piezoresistive sensors while reducing sensor
size. The advantage and disadvantage of these piezoresistors are compared to those of piezoelectric sensors.
Experimental results reveal that the MEMS piezoelectric sensors are able to achieve a better resolution than
piezoresistors, while piezoresistors can be built in much smaller areas. Both types of the MEMS strain sensors
are capable of high sensitivity measurements, subject to differing constraints.
As data densities in computer hard disk drives increase, airflow-induced vibration of the disk drive suspension becomes a major barrier to positioning the read-write head with sufficient precision. One component in reducing these vibrations is a dedicated sensor system for detecting vibration on the sensor arm directly, which enables high-frequency sampling and modal selectivity. In this paper, an efficient method for identifying optimal position and shape of piezoelectric strain gages on a flexible structure is presented, and applied to the steel suspension of a hard disk drive. Zinc oxide deposition processes are adapted to steel substrates, and used to fabricate miniature zinc oxide strain gages at the optimal strain gage location. Substrates with sensors installed were assembled into full disk drive suspensions and tested in a commercial disk drive.