Year of Publication

2010

Degree Name

Doctor of Philosophy (PhD)

Document Type

Dissertation

College

Engineering

Department

Chemical Engineering

First Advisor

Dr. J. Zach Hilt

Abstract

There is significant interest in the development of hydrogels and hydrogel nanocomposites for a variety of biomedical applications including drug delivery, sensors and actuators, and hyperthermia cancer treatment. The incorporation of nanoparticulates into a hydrogel matrix can result in unique material characteristics such as enhanced mechanical properties, swelling response, and capability of remote controlled (RC) actuation. In this dissertation, the development of hydrogel nanocomposites containing magnetic nanoparticles/carbon nanotubes, actuation with remote stimulus, and some of their applications are highlighted.

The primary hydrogel nanocomposite systems were synthesized by incorporation of magnetic nanoparticles into temperature responsive N-isopropylacrylamide (NIPAAm) matrices. Various nanocomposite properties were characterized such as temperature responsive swelling, RC heating with a 300 kHz alternating magnetic field (AMF), and resultant collapse. The nanoparticle loadings and hydrogel composition were tailored to obtain a nanocomposite system that exhibited significant change in its volume when exposed to AMF. The nanocomposites were loaded with model drugs of varying molecular weights, and RC pulsatile release was demonstrated.

A microfluidic device was fabricated using the low temperature co-fired ceramic (LTCC) processing technique. A magnetic nanocomposite of PNIPAAm was placed as a valve in one of the channels. The remote controlled liquid flow with AMF was observed for multiple on-off cycles, and the kinetics of the RC valve were quantified by pressure measurements.

The addition of multi-walled carbon nanotubes (MWCNTs) in NIPAAm matrices was also explored for the possibility of enhancement in mechanical properties and achieving remote heating capabilities. The application of a radiofrequency (RF) field of 13.56 MHz resulted in the remote heating of the nanocomposites. The intensity of the resultant heating was dependent on the MWCNT loadings.

In order to further understand the RC actuation phenomenon, a semi-empirical heat transfer model was developed for heating of a nanocomposite disc in air. The model successfully predicted the temperature rise as well as equilibrium temperatures for different hydrogel dimensions, swelling properties, nanoparticles loadings, and AMF amplitude. COMSOL was used to simulate temperature rise of the hydrogel nanocomposite and the surrounding tissue for hyperthermia cancer treatment application.

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