Publication Date

2018-08-09

Availability

Embargoed

Embargo Period

2020-01-31

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Mechanical Engineering (Engineering)

Date of Defense

2018-07-30

First Committee Member

Emrah Celik

Second Committee Member

Landon R. Grace

Third Committee Member

Victoria Coverstone

Fourth Committee Member

Ryan Karkkainen

Abstract

Poly(Styrene-block-Isobutylene-block-Styrene) is a phase-separated tri-block thermoplastic elastomer known for having excellent biocompatibility and flexibility. The mechanical properties of this material can be tailored by varying its styrene content. This makes it an excellent candidate for biomedical applications. SIBS reinforced with carbon black (CB) filler particles can be used for pressure sensing external (stick-to-skin) devices. Pressure sensors made from SIBS/CB composites can be used as potential solutions for real-time monitoring of intraoperative intraocular pressure. Another target application is the detection and prevention of pressure ulcers in people suffering from peripheral neuropathy, including diabetic patients. These sensors must be sensitive to pressure, biocompatible, conformable to complex surfaces, and capable of enduring the variable mechanical stresses associated with moving and stretching. The aim of this thesis is to fabricate, tests, and develop SIBS/CB composites for pressure sensing applications. The mechanical, electrical, morphological, and rheological properties of SIBS/CB composites are characterized. Biocompatibility retention is analyzed and the suitability of SIBS/CB composites for external pressure sensing applications is determined. Main challenges facing the development of new biomaterials include biocompatibility, good processability, flexibility, and functionality. In this thesis, SIBS/CB composites of different loadings are fabricated through a combination of high-shear mixing, ultrasonication, and solvent-casting. It is found that nanoscale CB can be easily and effectively dispersed in a SIBS host. The relationship between mechanical and electrical properties is established through analysis via tensile testing, resistivity testing, Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). Typically, an increase in electrical properties leads to reduction in mechanical properties. These properties are affected by the fabrication method and procedures utilized, further emphasizing the tailorability of SIBS/CB composites. For this reason, processing parameters are analyzed via statistical Taguchi and screening methods, leading to regression models for maximum tensile strength and conductivity responses. Addition of CB filler material to a polymer matrix alter the rheological properties of the material. The rheological behavior of conductive polymer composites has practical importance. It influences the final structure of the material and is valuable in determining the optimal processing conditions for manufacturing production. Rheological behavior of SIBS/CB composites is evaluated and provides insight into the interactions present in the composite. Finally, cell toxicity assays are used to determine whether addition of CB filler compromises the excellent biocompatibility present in the neat SIBS polymer. Biocompatibility testing results justify further exploration of SIBS/CB composites for biomedical testing. This thesis and all the data provided serve as foundational knowledge in the development of SIBS/CB composites. The information provided serves as guidelines for the development and fabrication of optimally functioning biocompatible pressure sensors for biomedical applications.

Keywords

composite; thermoplastic; biocompatibility; pressure sensor; mechanical testing; SIBS

Available for download on Friday, January 31, 2020

Share

COinS