Biopackaging of Intracranial Pressure Microsystem for Multimodality Neuro Monitoring of Severe Head Injury Patients

摘要

In this work, we present the biopackaging and integration method of an intracranial pressure microsystem for multimodal neural monitoring. The neural monitoring chip used is a System-on-Chip (SoC) which has Microelectromechanical Systems (MEMS) capacitive pressure sensor that is fabricated in-house after Complementary Metal-Oxide Semiconductor (CMOS) wafer fabrication process, with a temperature sensor and an oxygen sensor in order to achieve multimodal neural monitoring functions. Polyimide is used for the substrate of the SoC die and passive component due to its biocompatibility and flexibility. A reversed stand-off stitch wire bonding process was employed in order to achieve a low-profile wire looping for the interconnection of the SoC die to the substrate. The biocompatible coatings of this implantable system consist of Parylene-C (for covering temperature and pressure sensors), Nafion® (for covering oxygen sensor), and medical grade silicone elastomer (for overall device encapsulation). The ICP microsystem wireless reader module was packaged in a customized biocompatible hermetic Teflon housing. To reinforce and seal the catheter, which is integrated with the microsystem, during the device implantation into the brain tissue, it is filled until the wire bonded portion with polydimethylsiloxane. Similarly, the guiding tip of the catheter which will facilitate the sensor device to penetrate into the brain tissue is made and casted from a specially designed mold using polydimethylsiloxane as the material. Verification of the packaging feasibility was measured by measuring the sensitivities of the pressure sensor, oxygen sensor, and temperature sensor. The whole microsystem also passed the ISO 10993-5 standards in vitro cytotoxicity test with a conclusion of no reactivity and no cell lysis cell growth in cell culture, verifying its biocompatibility