Wirelessly Interrogated, Implantable Capacitive MEMS Sensors for Continuous Intraocular Pressure Monitoring.

Area of Science:

• Biomedical Engineering
• Sensor Technology
• Ophthalmology

Background:

• Continuous intraocular pressure (IOP) monitoring is crucial for managing glaucoma.
• Existing IOP monitoring methods often lack continuous, real-time capabilities or require invasive procedures.

Purpose of the Study:

• To develop and characterize a wirelessly interrogated microelectromechanical system (MEMS) capacitive sensor for continuous IOP monitoring.
• To investigate the sensor's performance over a clinically relevant pressure range (0-50 mmHg).

Main Methods:

• A passive inductor-capacitor (LC) tank circuit was designed with a spiral inductor and a variable-gap capacitive transducer.
• The capacitive transducer features a 500 µm × 500 µm × 2 µm membrane with a 2.5 µm gap, sensitive to pressure-induced deflection.
• Wireless interrogation was achieved using mutual inductive coupling between the sensor's LC circuit and an external readout coil.

Main Results:

• The MEMS capacitive sensor demonstrated a functional relationship between applied pressure and changes in the LC circuit's frequency and phase response.
• The sensor showed potential for real-time, continuous IOP monitoring within the 0-50 mmHg range and beyond.
• Mutual inductive coupling proved to be a viable readout mechanism for the passive sensor.

Conclusions:

• The developed wirelessly interrogated MEMS capacitive sensor offers a promising platform for continuous IOP monitoring.
• This technology could lead to improved glaucoma management through real-time pressure feedback.
• Further development may enable less invasive and more frequent IOP assessments.