Development of an Implantable Capacitive Pressure Sensor for Biomedical Applications

Area of Science:

• Biomedical Engineering
• Sensor Technology
• Materials Science

Background:

• Accurate in-vivo monitoring requires miniaturized, biocompatible sensors capable of measuring multiple physiological parameters.
• Existing sensors often lack integration, increasing device complexity and invasiveness for simultaneous measurements.

Purpose of the Study:

• To develop and characterize a subminiature, implantable capacitive pressure sensor with integrated temperature sensing for biomedical applications.
• To evaluate the sensor's performance, stability, and biocompatibility in a physiological environment.

Main Methods:

• Fabrication of a capacitive pressure sensor using silicon nitride (SiN) diaphragms and a polysilicon (p-Si) sacrificial layer via microelectromechanical systems (MEMS) technology.
• Integration of a resistive temperature sensor onto the same device using the p-Si layer.
• Packaging the sensor in biocompatible, needle-shaped metal housing.
• Performance testing in physiological saline solution, including sensitivity, hysteresis, and long-term stability assessments.

Main Results:

• The subminiature sensor (0.5 × 1.2 mm) achieved a sensitivity of 1.73 pF/bar and 1.7% hysteresis.
• The device demonstrated stable operation for 48 hours without degradation in a saline environment.
• The integrated temperature sensor showed a linear response with a temperature coefficient of resistance (TCR) of 0.25%/°C.

Conclusions:

• The developed MEMS sensor enables simultaneous, accurate measurement of pressure and temperature in a single, miniaturized, implantable device.
• The sensor's biocompatible packaging and robust performance confirm its suitability for long-term biomedical monitoring.
• This integrated sensor technology offers a cost-effective solution for advanced in-vivo diagnostics.