Packaging a piezoresistive pressure sensor for intracranial pressure monitoring

As clinical monitoring of intracranial pressure is critical to the treatment of brain diseases, the piezoresistive implantable intracranial pressure (ICP) sensor based on silicon bulk micromachining technology for medical applications has been developed. In this paper, the design, fabrication and test of the sensor are described. The sensitivity of this ICP sensor is greatly increased while the size is kept small. By analyzing the stress distribution of sensitive element with finite element method, the size and structure of the sensor are determined. Fabricated on an n-type single crystal silicon wafer, the sensor chip is mounted in the capsule. The packaging materials of the sensor are of biocompatibility and high workability. Test results demonstrate that the sensor features a sensitivity of 10 μV/V/mmHg at room temperature, exhibits a linear response over an operating pressure range of -10-35 KPa (-75-250 mmHg), and the output non-linearity is less than 1.2%. The proposed configuration presents its advantages in drift characteristic, absolute accuracy and sensitivity compared with the implanted ICP sensor developed before. Due to the tiny dimension, good reliability and biocompatibility, the sensor has a potential used for biomedical application.