Hermetic and Bioresorbable Packaging Materials for MEMS Implantable Pressure Sensors: A Review

Pressure sensors based on microelectromechanical system (MEMS) technology have been employed for measuring the pressure inside the human body due to their small size, lightweight, and low energy consumption. Hermetic packages are necessary to protect the implants from body fluid corrosion. Materials such as metal and glass are usually considered to be hermetic and can ensure several years of lifetime. Materials with low permeability, such as liquid crystal polymers and parylene, are also supposed to be short-term hermetic when the expected lifetime is not too long (less than a year). Water penetration and interface adhesion determine whether the package fails. Helium leakage tests and water concentration tests can be used to predict when the package fails. In addition, for more short-term implantable devices (several days or weeks), bioabsorbable packages can be helpful. The main advantage is that the self-degradation of the packaging material can avoid tissue damage caused by long-term implantation or infection caused by secondary removal surgery.