Publications & Presentations

The development of effective regenerative therapies for spinal cord injury is hindered by two major barriers: the lack of structurally optimized bridging scaffolds and the inability to monitor biological integration in real time. This thesis addresses both challenges through a dual-objective framework.

Three scaffold materials — polycaprolactone, poly(lactic-co-glycolic acid), and silicone — were evaluated through extrusion-based direct ink writing at channel widths of 200 µm, 400 µm, and 600 µm. PCL with a 400 µm pore size emerged as the strongest candidate because it combined surgical toughness with strong in vitro support for neural progenitor cell viability. PLGA was found to create cytotoxic acidic microenvironments through hydrolytic degradation.

Complementing the scaffold work, a chronic dorsal spinal imaging window was designed and surgically validated in a rat model. Inspired by surgical retractors, the device used 3D-printed teeth to hold tissue open and a flush-mounted PET optical film to provide stable, long-term in vivo visualization.

This study evaluates the rate of tensile strength loss in sutures subjected to hydrolysis, providing surgeons with data to predict wound-closure risks. Absorbable sutures degrade through hydrolysis in moisture-rich settings, and rapid degradation in spinal surgeries can contribute to wound reopening, delayed healing, and infection.

A custom degradation chamber was built to replicate in vivo conditions using phosphate-buffered saline at 37°C with pre-tensioned loads for different suture sizes. Weekly tensile testing over five weeks followed ASTM D2256-02 standards with surgeon-prepared samples.

Peripheral intravenous insertion is a common clinical procedure, but failed attempts — especially in pediatric and small-vein patients — cause pain, anxiety, and delays. Manual techniques such as massage and warming are often used but are not standardized or validated.

This project developed a thermal massaging tourniquet combining a tourniquet cuff, targeted vibration motors, and a heating filament above the cubital fossa. Ultrasound imaging quantified cephalic vein cross-sectional area across test conditions, while transient conduction simulation informed safe temperature targets and heating duration.

Extrusion-based 3D bioprinting of biodegradable polymers such as PCL and PLGA relies on solvent evaporation to generate the microporosity needed for cell infiltration and nutrient transport. This paper examines how coupled convective heat and mass transfer at the filament-air interface governs pore formation, and how that architecture influences the scaffold's effective thermal conductivity.

The analysis builds a coupled energy-mass balance framework in which the convective heat-transfer coefficient provides latent heat for vaporization and the mass-transfer coefficient governs vapor removal. Environmental parameters such as airflow velocity, ambient temperature, and solvent vapor concentration are identified as key process levers, connecting manufacturing conditions directly to thermal performance in the final scaffold.