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The Design of a Biodegradable Stent for Arteriovenous Fistula Maturation and a Carbon Nanotube Membrane for Water Filtration

Xu, Chenhao
http://orcid.org/0000-0001-7936-2415
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1659518544418528

Abstract Details

2022, PhD, University of Cincinnati, Engineering and Applied Science: Mechanical Engineering.
This dissertation developed two devices based on ion exchange in electrolytic solutions. A magnesium biodegradable stent was designed to dissolve in blood vessels within a short period of time whereas a conventional stent stays in the body forever. Due to the brittleness of magnesium alloys, the major challenge was designing the geometry of the struts in the stent. The magnesium stent must expand in a blood vessel like a stainless-steel stent without fracturing. In this dissertation, the design of a balloon-expandable biodegradable stent was proposed. Design, simulation validation, prototype development, and in-vivo animal experimentation were performed. The stent had a maximum Von Mises stress of 279 MPa with plastic deformation strain of 9.6%. The recoiling ratio (percent the stent contracts after plastic expansion) of the stent was 5.27% and the radial stiffness at the recoiled state was 1.45 N/mm. The stent in the in-vivo animal experiment was characterized using ultrasound, CT scan, and micro-CT scan. The blood vessel in which the biodegradable stent was placed showed a larger lumen diameter and higher blood flow 4-weeks and 8-weeks after implantation. In addition, the stent design was optimized, and two new designs were proposed, a magnesium large coverage stent and a magnesium self-expanding stent. The large coverage stent covered the area the first-generation stent design could not reach in the Arteriovenous Fistula (AVF) application. The self-expandable stent was proposed for easy delivery and reducing neointimal hyperplasia. The unique design allows a magnesium stent to self-expand. However, the long stent length and limited crimping size restrict the range of self-expansion. The second device developed in the dissertation was a carbon nanotube (CNT) membrane to filter water. The CNT membrane was synthesized to adsorb particles, natural organic matter (NOM), and heavy metals from water. The filtering mechanism is based on removing multiple ions from solution. The CNT membrane was synthesized using the gas phase pyrolysis method for manufacturing nanotube sheet. Both pristine carbon nanotube (PCNT) sheet and hybrid carbon nanotube (HCNT) sheet (synthesized with micro-size activated carbon) were made in a high temperature custom reactor. These CNT membranes mainly focused on the adsorption of lead ions and NOM. These different membranes combined with conventional filter materials were tested in a series of comparison experiments. Prior to the experiments, PCNT and HCNT membranes were acid treated for different times. Inductively Coupled Plasma - Mass Spectroscopy (ICP-MS) and thermogravimetric analysis (TGA) were used to analyze the water and membrane samples post experiment. The results showed PCNT/HCNT membranes with 120 minutes of acid treatment removed the most lead from water. PCNT membranes performed better than HCNT membranes. On the other hand, the HCNT membranes adsorbed more NOM than PCNT membranes due to the micro activated carbon. Therefore, the HCNT membrane combined advantages of both materials.
Mark Schulz, Ph.D. (Committee Member)
Ying Hong, PhD (Committee Member)
Zhangzhang Yin, Ph.D. (Committee Member)
Jing Shi, Ph.D. (Committee Member)
Woo Kyun Kim, Ph.D. (Committee Member)
136 p.
Mechanical Engineering
Magnesium; Biodegradable Stent; carbon nanotube; Water Filtration

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Citations

  • Xu, C. (2022). The Design of a Biodegradable Stent for Arteriovenous Fistula Maturation and a Carbon Nanotube Membrane for Water Filtration [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1659518544418528

    APA Style (7th edition)

  • Xu, Chenhao. The Design of a Biodegradable Stent for Arteriovenous Fistula Maturation and a Carbon Nanotube Membrane for Water Filtration. 2022. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1659518544418528.

    MLA Style (8th edition)

  • Xu, Chenhao. "The Design of a Biodegradable Stent for Arteriovenous Fistula Maturation and a Carbon Nanotube Membrane for Water Filtration." Doctoral dissertation, University of Cincinnati, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1659518544418528

    Chicago Manual of Style (17th edition)

ucin1659518544418528
39
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This open access ETD is published by University of Cincinnati and OhioLINK.