Anti-Biofouling Implantable Catheter Using Thin-Film Magnetic Microactuators

Qi Yang, Purdue University

Abstract

The dissertation includes two independent chapters which investigated the experiences of individuals with disabilities in connection with societal attitudes regarding disability. The first article is a systematized review which analyzes and synthesizes the existing literature on implicit and explicit disability attitudes across multiple domains (e.g., educational; occupational; healthcare). Chapter 1 identifies common themes across the existing literature and identifies potential predictors and buffers of negative disability attitudes. The article concludes with a call to counseling psychologists to address negative disability attitudes utilizing the roles and themes of the field. Finally, suggestions are made regarding the development and implementation of interventions to help address negative disability attitudes and the subsequent harmful effects. The second article is an empirical study that examines factors related to the persistence intentions of individuals with disabilities to address the high attrition rates of this population within postsecondary environments. A moderated mediation model is proposed to address four hypotheses. First, I hypothesized academic self-efficacy would mediate the relationship between stereotype threat and persistence intentions. Second, coping self-efficacy would mediate the relationship between stereotype threat and persistence intentions. Third, social self-efficacy would mediate the relationship between stereotype threat and persistence intentions. Fourth, I hypothesized that endorsing a growth mindset would buffer against the negative indirect relationship between stereotype threat and persistence intentions which operate through academic self-efficacy. Data were collected from postsecondary students who identified as having one or multiple diagnosed disabilities at a large public university in the Midwest. The study results supported my first hypothesis that academic self-efficacy would significantly mediate the relationship between stereotype threat and persistence intentions. Additionally, the results revealed that high levels of perceived stereotype threat were associated with lower levels of coping self-efficacy and social self-efficacy, as the researcher anticipated. However, our second and third hypotheses were rejected due to these mediating factors not significantly influencing a participants’ intentions to persist within the academic environment. Finally, the results suggested that one’s mindset of intelligence was a positive main effect predictor of academic self-efficacy. However, contrary to our fourth hypothesis, mindset of intelligence did not significantly moderate the negative indirect relation between stereotype threat and persistence intentions that operate through academic self-efficacy. 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 selfclearing 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 bench-top 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.

Degree

Ph.D.

Advisors

Irazoqui, Purdue University.

Subject Area

Design|Surgery|Electromagnetics|Medicine|Physics

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