Prolonged Corrosion Stability of a Microchip Sensor Implant during In Vivo Exposure

Area of Science:

• Biomedical Engineering
• Materials Science
• Implantable Biosensors

Background:

• Continuous glucose monitoring is vital for managing metabolic conditions.
• Biostability of implantable biosensors remains a challenge, particularly concerning semiconductor surface degradation.
• Previous studies indicated corrosion issues with complementary metal-oxide-semiconductor (CMOS) biosensors in vivo.

Purpose of the Study:

• To evaluate the in vivo biostability of a microelectronic biosensor chip after prolonged implantation in cattle.
• To assess the impact of a semipermeable membrane on the integrity of exposed semiconductor surfaces.
• To determine the suitability of microelectromechanical system (MEMS) technology for long-term biosensor implants.

Main Methods:

• Implantation of a hermetically sealed microelectronic biosensor system near the Trapezius muscle in cattle for 17 months.
• Explantation and comparative analysis of the microelectromechanical system (MEMS) chip against unexposed controls.
• Surface analysis using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Energy-Dispersive X-ray (EDX) mapping.

Main Results:

• The explanted sensor chip exhibited no signs of corrosion after 17 months of in vivo exposure.
• The topmost passivation layer of the microelectromechanical system (MEMS) chip remained intact, showing no degradation.
• Negligible corrosive attack was observed, attributed to the presence of the semipermeable membrane separating the sensor assay from the surrounding tissue.

Conclusions:

• The semipermeable membrane significantly enhances the biostability of implantable biosensor chips.
• This finding is highly relevant for the development of durable and reliable biosensor implants for continuous monitoring.
• The study highlights the potential of CMOS/BiCMOS MEMS technology for advanced, long-term biomedical applications.