Publications & Presentations
3D Printing of a Biocompatible Scaffold and a Real-Time Imaging Window for Monitoring Rat Spinal Cord Regeneration
University of Minnesota – Twin Cities | Advisors: Dr. Michael C. McAlpine & Dr. Ann M. Parr
The development of effective regenerative therapies for spinal cord injury (SCI) is currently hindered by two fundamental barriers: the lack of structurally optimized bridging scaffolds and the inability to monitor biological integration in real-time. This thesis addresses both limitations through a dual-objective framework.
Three candidate scaffold materials — Polycaprolactone (PCL), Poly(lactic-co-glycolic acid) (PLGA), and Silicone — were evaluated via extrusion-based Direct Ink Writing (DIW) at channel widths of 200 µm, 400 µm, and 600 µm. PCL with a 400 µm pore size emerged as the optimal candidate, offering superior tensile toughness for surgical implantation and the best in vitro support for dorsal and ventral spinal neural progenitor cell (NPC) viability over 50 days post-differentiation. PLGA was found to create cytotoxic acidic microenvironments through hydrolytic degradation.
Complementing the scaffold work, a novel chronic dorsal spinal imaging window was designed, fabricated from FormLabs Dental Clear LT V2 resin, and surgically validated in a rat model. The device, inspired by surgical retractors, uses 3D-printed teeth to mechanically hold paraspinal tissue open and a flush-mounted PET optical film to provide stable, long-term, high-resolution in vivo visualization — overcoming the "black box" problem of traditional preclinical SCI research.
Testing the Hydrolysis-Driven Degradation of Sutures: Impacts on Tensile Strength Over Time
Undergraduate Research Opportunities Program (UROP) | University of Minnesota – Twin Cities
This study evaluates the rate of tensile strength loss in sutures subjected to hydrolysis, providing surgeons with critical data to predict and mitigate risks associated with suture degradation in high-stress environments such as the fascia layer. Absorbable sutures degrade primarily through hydrolysis in high-moisture environments, and rapid degradation in spinal surgeries can lead to wound reopening, delayed healing, and infection.
A custom degradation chamber replicating in vivo conditions (37°C phosphate-buffered saline, pre-tensioned loads of 10N, 25N, and 40N for sizes 2-0, 1-0, and 0) was used to track tensile strength weekly over five weeks. Suture tensile testing followed ASTM D2256-02 standards using a stainless steel fixture simulating the fascia layer curvature. Sutures were prepared by a professional surgeon in a sterile setting to ensure clinical relevance.
Thermal Massaging Tourniquet: Venodilation Optimization Using Heat, Vibration, and Compression
ME 4054W: Design Projects | University of Minnesota – Twin Cities | Sponsor: Dr. Jonathan Strutt, MD
Peripheral intravenous (PIV) insertion is a ubiquitous clinical procedure, but failed attempts — particularly in pediatric and small-vein patients — cause pain, anxiety, and procedural delays. Non-standardized manual techniques like heat and massage are commonly employed alongside tourniquets to dilate veins, but lack automation, standardization, or validated efficacy data.
This project developed a thermal massaging tourniquet combining a tourniquet cuff (40–90 mmHg), four targeted vibration motors, and a heating filament embedded above the cubital fossa, all controlled independently via an on/off switch system. Ultrasound imaging was used to measure cephalic vein cross-sectional area across six test conditions. A 2D transient conduction simulation modeled heat propagation through epidermis, dermis, and hypodermis to the cephalic vein, confirming safe operating temperatures (98.5–122°F) and informing the heating duration protocol.
Convection-Driven Thermal and Mass Transfer in 3D Bioprinting: Micropore Formation and Heat Transfer in PCL and PLGA Scaffolds
ME 8342: Advanced Heat Transfer | University of Minnesota – Twin Cities
Extrusion-based 3D bioprinting of biodegradable polymers (PCL and PLGA) dissolved in volatile solvents relies on solvent evaporation to generate the microporosity essential 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 the resulting architecture in turn determines the effective thermal conductivity of the solidified scaffold.
The analysis develops a coupled energy-mass balance framework: the convective heat transfer coefficient h supplies latent heat for vaporization while the mass transfer coefficient hm governs vapor removal. Environmental parameters — airflow velocity, ambient temperature, and solvent vapor concentration — are identified as key control levers. Flat-plate Nusselt and Sherwood correlations (Nux = 0.332 Re1/2 Pr1/3) and the Chilton-Colburn analogy are applied to quantify and relate these coefficients. The paper closes by analyzing conduction-dominated heat transfer in the solidified scaffold using effective thermal conductivity models (keff), directly linking fabrication process control to in vivo thermal performance.