| dc.description.abstract | Minimally Invasive Surgery (MIS) pursues the highest attention in various medical procedures globally because of the reduced complicated process compared with traditional surgery, short postprocedural convalescence, and reduction in hospital expenditure cost. Although the minimally invasive procedures have several advantages, there exist challenges during such procedures due to the lack of direct view of the location and position of the catheter, operating in narrow space, and lack of sensation while operating. Hence, it requires specific surgical tools (such as catheters and fine instruments) and techniques to perform the surgery. For a few decades, surgeries like cardiac ablation, which is used to treat cardiac arrhythmia using RF ablation, have been performed using MIS. However, in these applications, very long, flexible, and thin catheters that can be deflected either in single or bidirectional ways are required for performing the surgery.
Additionally, these catheters require force sensors on their distal end to measure contact force between the cardiac tissue and the electrode tip. The force between the tip and the tissue indicates energy delivered to the tissue and lesion formation. In general, an optimum force between 0.2 N to 0.3 N is applied for effective lesion formation and to avoid other complications. Though the ablation catheters integrate the force sensor, most of the existing manual ablation catheters do not provide haptic feedback to the electrophysiologists while performing the surgery. Hence, the lack of haptic feedback on the catheter will necessitate extensive operator skills and experience. With haptic feedback, it may potentially aid the electrophysiologists in undertaking complex ablations. In addition, the sensor's resolution can estimate the effective tip-tissue contact with high accuracy, differentiate the forces acting on the catheter tip, and provide haptics to represent the force and its position qualitatively.
This thesis presents the design, simulation, fabrication, characterization, and performance study of Micro-Electro-Mechanical-Systems (MEMS)-based force sensors for real-time measurement of catheter tip contact force. The detection of force is due to the deformation of the micro-bridge structures on the MEMS device. Different sensors designs have been analyzed and simulated using finite element modeling (FEM) tools to optimize the sensor micro-bridge structures and determine stress distribution across the bridge. Additionally, with the help of FEM simulation, the placement and optimization of the piezoresistive sensing elements have been determined. Furthermore, the sensor fabrication process executed using advanced micromachining techniques and thin-film metallization has been discussed. The integration of the fabricated force sensor with the catheter tip for the tip contact force measurement has been investigated. A novel approach to integrate MEMS-based piezoresistive force sensor within a catheter tube is shown with multiple innovations in sensor packaging technology such as the force transfer structure and pogo-pin assembly. A facile 3D-integrated sensor packaging (using plastic, PCB, and spring-loaded pins) to realize electrical interconnections between the fabricated force sensor and measurement system is presented, which can be adapted for various medical, industrial, electronics, and telecommunication applications. Different vibration patterns to determine the forces acting on the tip have been examined and implemented. The interfacing of the sensor to the vibration motors for providing haptic feedback to the operator has been discussed. Finally, the sensors have been characterized and validated by integrating with the customized catheter tip by applying known input force on the tip. The sensor response is linear and repeatable with no hysteresis up to the required force range. Finally, a working catheter model integrated with a force sensor and vibro-haptic feedback mechanism has been demonstrated on porcine heart tissues. | en_US |
