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

In this work, we present the biopackaging andintegration method of an intracranial pressure microsystemfor multimodal neural monitoring. The neural monitoring chipused is a System-on-Chip (SoC) which hasMicroelectromechanical Systems (MEMS) capacitive pressuresensor that is fabricated in-house after Complementary Metal-Oxide Semiconductor (CMOS) wafer fabrication process, witha temperature sensor and an oxygen sensor in order to achievemultimodal neural monitoring functions. Polyimide is used forthe substrate of the SoC die and passive component due to itsbiocompatibility and flexibility. A reversed stand-off stitchwire bonding process was employed in order to achieve a lowprofilewire looping for the interconnection of the SoC die tothe substrate. The biocompatible coatings of this implantablesystem consist of Parylene-C (for covering temperature andpressure sensors), Nafion® (for covering oxygen sensor), andmedical grade silicone elastomer (for overall deviceencapsulation). The ICP microsystem wireless reader modulewas packaged in a customized biocompatible hermetic Teflonhousing. To reinforce and seal the catheter, which is integratedwith the microsystem, during the device implantation into thebrain tissue, it is filled until the wire bonded portion withpolydimethylsiloxane. Similarly, the guiding tip of the catheterwhich will facilitate the sensor device to penetrate into thebrain tissue is made and casted from a specially designed moldusing polydimethylsiloxane as the material. Verification of thepackaging feasibility was measured by measuring thesensitivities of the pressure sensor, oxygen sensor, andtemperature sensor. The whole microsystem also passed theISO 10993-5 standards in vitro cytotoxicity test with aconclusion of no reactivity and no cell lysis cell growth in cellculture, verifying its biocompatibility