A 0.9m Long 0.5gf Resolution Catheter-based Force Sensor for Real-Time Force Monitoring of Cardiovascular Surgery

This paper presents a 0.9m long capacitive force sensor for a catheter integration, which measures a contact force to inner vessel wall or organs with a resolution of 0.5gf. The force sensor is implemented with a thin flexible printed circuit board (FPCB) encapsulated by a force sensitive medium, multilayer polydimethylsiloxane (PDMS). The parasitic capacitance $( \mathrm {C}_{P})$ inherent in long catheters significantly degrades the sensing accuracy of capacitive force sensors. To account for this, this work proposes a sensor interface with $\mathrm {C}_{P}$ canceller. By removing the 348pF (91.5%) of $\mathrm {C}_{\mathrm{P}}$with the $\mathrm {C}_{\mathrm{P}}$ canceller, the capacitive force sensor achieves a capacitance resolution of 16aF equivalent to a force error of 0.5gf, which is a $10 \times $ improvement compared to the conventional sensor interface. The proposed force sensor offers great potential for real-time force monitoring of cardiovascular surgery.