Poster J18 - Resolution, mechanical properties and biocompatibility of resin printed parts

Friday, October 25, 2024

3:30 PM - 4:30 PM EST

Location: Exhibit Hall E, F & G

Presenting Author(s)

Nicholas Featherstone

Student
Lawrence Technological University, United States

Co-Author(s)

Madeline Bradshaw (she/her/hers)

Student
Lawrence Technological University
Warren, Michigan, United States
MR

Moorea Ramessar (she/her/hers)

Student
Lawrence Technological University
Farmington Hills, Michigan, United States
GS

Grace Sun

Student
Troy High School, United States
Andrew Ulaszek

Project Engineer
Lawrence Technological University, Michigan, United States

Last Author(s)

YL

Yawen Li, PhD

Associate Professor and Chair, Biomedical Engineering Department, Lawrence Technological University
Lawrence Technological University
Southfield, Michigan, United States

Introduction: Resin printing, specifically masked stereolithography (MSLA), is a rapidly growing process to create 3D structures due to its versatility in the material selection and high resolution features that can be achieved with fast turnaround time and low cost. Mechanical properties and biocompatibility are important considerations when using these printed resin parts for biomedical applications. The goal of this study was to test the print resolution of a commercial resin and evaluate the mechanical properties and in-vitro biocompatibility of the printed structures. The results will be used to guide continuing surface modification work and improve the biocompatibility of the printed resin parts.

Materials and

Methods: An epoxy acrylate based resin was used to create disks, tensile test samples, and micro-resolution arrays on a Saturn 3 Ultra resin printer. The printing parameters follow that recommended by the resin supplier, excluding a reduced initial layer cure time, a horizontal expansion factor, and additional post-processing (cleaning and UV curing).
The micro-resolution arrays were imaged under a microscope and dimension accuracy measurements were made. Tensile test samples were subjected to uniaxial tensile loading till fracture. Printed resin disks were leached in phosphate buffered saline (PBS) for two days. Some disks were then treated with oxygen plasma and/or fibronectin coating. Human dermal fibroblasts were seeded on the disks at 50,000 cells/cm2 density and cultured for 4 days. The cell viability was characterized using an alamarBlue assay. Surface adhesion and plasma treatment was investigated through contact angle measurements.

Results, Conclusions, and Discussions: Results and Discussion
An average resolution size of 19-24 μm (in X-Y) was achieved from the resin printing (Fig. 1). The tensile testing gave a Young’s modulus of 1.7 GPa, an ultimate tensile strength of 36 MPa, and fracture strain of 3.9% (Fig. 2). These mechanical property data showed higher modulus and lower fracture strain than data from the resin supplier, suggesting that the printing and post-processing parameters likely affected the properties of the material.
Cells seeded on the printed resin with different treatment all showed lower viability than cells seeded on the cover glass controls (Fig. 3). The results were consistent with SEM images (Fig. 4), which showed normal fibroblast morphology on cover glass (a), compared to much lower cell count with cell fragments on the resin surface (b). Although oxygen plasma treatment dramatically decreased the water contact angle from 53° to 11°, no obvious change in fibroblast viability was observed. A most likely reason for the low cell viability could be incomplete leaching of toxic ingredients from the printed resin, rendering subsequent surface modification ineffective.
Conclusions
Resin printing with an average resolution of 19-24 μm was achieved. Changes in the printing and post-processing conditions led to higher modulus and lower fracture strain for the printed resin. Our preliminary biocompatibility study showed poor cell viability on the resin surface. Ongoing work is focused on improved leaching processes and surface modification to enhance the cell viability.

Acknowledgements (Optional):