Johan Foster

Associate Professor

Research Classification

Research Interests

3D Printing
Biomaterials
Biomedical Devices
Bioproducts
Cellulose Nanomaterials
Fibers
Polymers

Relevant Thesis-Based Degree Programs

 
 

Graduate Student Supervision

Doctoral Student Supervision

Dissertations completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest dissertations.

Cellulose nanocrystals: from extraction to biomedical application (2021)

With societal, industrial, and clinical progress continuously reaching greater heights, the crucial need for enhanced materials with versatile properties is ever increasing to help this growth. As such, polymer nanocomposites (PNCs) have been heavily researched, becoming redefined as their own class of materials, focusing on fundamental structure/property relationships, manufacturing techniques, and commercial applications, due to their remarkable properties and application versatility. Through countless nanoparticle and polymer matrix variations, PNCs can be finely-tuned to exhibit a multitude of unique characteristics. Utilizing this concept, the research laid out in the combined chapters of this dissertation sought to produce various PNCs embedded with cellulose nanocrystals/nanofibrils (CNCs/CNFs) and magnetic nanoparticles (MNPs) to obtain uniquely tunable properties to further progress the biomaterials field for biomedical applications. Initially, CNCs were extracted from the otherwise useless agricultural waste product of spent coffee grounds through phosphoric acid hydrolysis, and analyzed using multiple physical and chemical characterization techniques. In particular, a few crucial properties determined were aspect ratio of 12 ± 3, crystallinity of 74.2%, surface charge density of 48.4 ± 6.2 mmol/kg cellulose, and the ability to successfully reinforce PNCs, comparing well to other literature data and common commercial CNCs. Following extraction, CNCs/CNFs, as well as MNPs, were incorporated into various polymer matrices, including poly(ethylene glycol) diacrylate, sodium alginate, gelatin, and polyurethane, among others. Through solution casting and 3D bioprinting fabrication methods, as well as composition manipulation, CNCs/CNFs were able to reach ideal percolating networks within the PNCs for maximum mechanical reinforcement with minimal hindrance of the polymer matrix’s natural properties. The various PNC hydrogel scaffolds successfully demonstrated tunability of their nanostructural, mechanical, hydration, and biodegradation properties, utilizing the benefits of manipulated composition, crosslinking density, and nanofiller orientation to increase versatility for tissue engineering constructs. Additionally, MNP incorporation was shown to successfully produce inductive heating responses to promote topographical shape memory effects, while invoking minute thermal dissipation into surrounding environments to reduce thermal shock to seeded biological components. The success of this work makes strides to overcome a few crucial disadvantages of current PNC biomaterial hydrogels, specifically their inability to regenerate biomimetic native tissues during wound healing.

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Master's Student Supervision

Theses completed in 2010 or later are listed below. Please note that there is a 6-12 month delay to add the latest theses.

Integrated bioprocessing concept: hemp hurd valorization by co-production of lignified nanomaterials, lactic acid and binderless fiberboards (2024)

This work seeks to conceptualize a novel pilot process for valorizing hemp hurd residues. Presented here are three proof-of-concept investigations and a simple gross profit analysis to motivate the development of a zero-waste, integrated biomaterials production process for co-production of lignified cellulose nanomaterials, lactic acid, and binderless fiberboards. The nanomaterials are produced by oxalic acid hydrolysis of unwashed ground hemp hurd to produce thermally resistant nanomaterials in two output streams separated by centrifugation. The colloidal supernatant from nanomaterial production is concentrated and dried by spray-freeze drying before inclusion in melt-processed PA-6 nanocomposites, which are tested for their mechanical properties. Binderless boards are produced by fluidized grinding of hemp hurd in a mass colloider followed by filtration and hot pressing in enclosed press molds. These boards are then tested for their material properties and compared to ANSI Basic Hardboard standards. The hydrolysate left over after nanomaterial production is combined with filtrate from the binderless board grinding process and a fermentation is conducted with Lactiplantibacillus plantarum to study productivity of lactic acid caused by introduction of hydrolysate to media. The results from these three sets of experiments are used to inform a mass balance and gross profit analysis on the integrated process concept proposed. A valorization factor of >7.4 is reported, based on a 1000 kg/day pilot-scale process. This finds daily gross profit between $3490-$8900, when only the input costs and output wholesale values of products are considered. The M1250 binderless fiberboard produced exceeded ANSI standards for type 1 hardboard. Nanocomposites of PA-6 with 1% loading showed a 21 ±2% increase in ultimate tensile strength, and a 71 ±1% increase in elastic modulus compared to the neat PA-6.

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Synthesis and valorization of uniform lignin nanoparticles by subcritical water/solvent systems (2023)

The full abstract for this thesis is available in the body of the thesis, and will be available when the embargo expires.

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Publications

 
 

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