A Parasitic Insensitive Catheter-Based Capacitive Force Sensor for Cardiovascular Diagnosis

Area of Science:

• Biomedical Engineering
• Sensor Technology
• Medical Devices

Background:

• Cardiovascular diagnosis requires precise force measurement.
• Existing capacitive sensors suffer performance degradation due to parasitic capacitance in long catheters.
• Need for robust and accurate force sensing in catheter-based interventions.

Purpose of the Study:

• To develop a catheter-based capacitive force sensor interface for cardiovascular diagnosis.
• To mitigate performance issues caused by parasitic capacitance in long catheters.
• To enhance the accuracy and resolution of force measurements in catheter applications.

Main Methods:

• Implementation of a capacitive force sensor on a flexible printed circuit board (FPCB) substrate with polydimethylsiloxane (PDMS).
• Development of a parasitic-insensitive analog front-end (AFE) with active parasitic capacitance (Cp) cancellation using a charge amplifier and negative capacitor.
• Testing of the prototype sensor with a force loader in whole blood and ex-vivo tissue differentiation.

Main Results:

• Successful cancellation of 348 pF parasitic capacitance in a 0.9-m sensor.
• Achieved a signal-to-noise ratio (SNR) of 53.8 dB and capacitance resolution of 16 aF, a 19.6 dB improvement.
• Demonstrated a force resolution of 2.22 gf (9.29x reduction) and distinguished tissue stiffness ex-vivo.

Conclusions:

• The proposed parasitic-insensitive AFE effectively cancels large parasitic capacitances in catheter-based capacitive force sensors.
• The developed sensor interface offers high sensitivity and resolution, enabling accurate force measurements.
• This technology facilitates the integration of smart capacitive force sensors into advanced catheter systems for improved cardiovascular diagnosis.