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ANTI-BIOFOULING IMPLANTABLE CATHETER USING THIN-FILM MAGNETIC MICROACTUATORS
Hydrocephalus is a neurological disease characterized by abnormal accumulation of cerebral spinal fluid (CSF) in ventricle of brain. 1 in 1000 newborns are affected each year and it is life-threatening if left untreated. The golden standard of treatment is to surgically implant a shunt that divert excessive CSF away from ventricle to alleviate intraventricular pressure (ICP) in patient. Unfortunately, shunt failure rate is notoriously high because of obstruction of catheter intake pore. The obstruction is primary caused by normal and inflammatory tissue (biofilm) buildup over time. Shunt replacement surgery is typically required after only 1 year of implantation for 40% of patients. To prolong the lifespan of hydrocephalus shunt, we previously proposed and designed magnetic micro-actuators platform to remove biofilm mechanically. Removal of muscle cells and microbeads were demonstrated from wafer level devices on bench-top.
To examine device efficacy in ventricular catheter, I developed magnetic actuator on polymer substrate. First, polyimide based flexible thin-film devices were microfabricated and integrated into a single-pore silicone catheter. A proof-of-concept self-clearing smart catheter was presented. Removal of microscopic biofilm was evaluated against bovine serum protein (BSA). Detachment of BSA up to 95% was achieved by shear stress from magnetic actuation. Next, I developed resistive deflection sensing using a metallic strain gauge, allowing device alignment with magnetic field for maximum energy delivery. In addition, auxiliary functionalities such as occlusion detection and flow rate measurement were demonstrated on catheter. Moreover, a new serpentine cantilever geometry with increased magnetic volume was proposed for improved delivery of torque and deflection. In a benchtop evaluation, we showed prolonged catheter drainage (7x) in a dynamic fluid environment containing macroscopic blood clots. Finally, using an intraventricular hemorrhage (IVH) porcine model, we observed that self-clearing catheter had longer survival than control catheter (80% vs. 0%) over the course of 6 weeks. Animals treated with magnetic actuation had significantly smaller ventricle size after 1 week of implantation.