Date of Award

8-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Committee Chair/Advisor

Dr. Xin Zhao

Committee Member

Dr. Garrett Pataky

Committee Member

Dr. Huijuan Zhao

Committee Member

Dr. Hongseok Choi

Abstract

Barbed sutures are designed to eliminate the need for surgical knots. In addition, it promotes more efficient wound closure, faster healing, and even tension distribution. While traditional mechanical cutting often produces rough edges and structural irregularities, this study demonstrates that femtosecond lasers can produce barbs with higher accuracy and precision than conventional methods. Furthermore, mechanical evaluations showed that the laser-fabricated barbs maintain robust tensile strength while demonstrating reliable tissue anchoring and high pull-out resistance.

Moreover, this study systematically investigates the effects of laser parameters (laser fluence, overlapping ratio, repetition rate, and scanning passes) on the ablation efficiency and surface quality of four biopolymers: Poly-4-hydroxybutyrate (P4HB), catgut, polypropylene, and polyester. A Taguchi L9 orthogonal array and statistical analysis of variance (ANOVA) were employed, and distinct material-specific sensitivities were identified. P4HB tends to exhibit high responsiveness to laser fluence and emerged as the dominant factor (48.75% contribution) in material removal, while causing severe thermal damage. On the other hand, natural collagen-based catgut required significantly higher energy. It was most sensitive to cumulative energy delivery via scanning passes (56.84% contribution) rather than to individual high-energy pulses, while also causing higher surface roughness.

Furthermore, the research highlights that femtosecond laser processing can induce substantial functional enhancements to the polymer surfaces without significantly compromising their bulk integrity. Quantitative topography mapping revealed that laser treatment doubled the effective surface area by creating intricate micro-porous networks and microfoam-like structures. This morphological modification was accompanied by localized surface oxidation and a notable increase in surface oxygen concentration.

Finally, the mechanical viability of the processed sutures was verified through Differential Scanning Calorimetry (DSC). The results demonstrated that the bulk crystallinity and melting temperature of both polypropylene and polyester remained stable after laser irradiation, which proves that the laser-matter interaction is effectively localized at the ablation front. From these results, it can be said that a femtosecond laser can produce high-quality cuts while preserving bulk integrity and enhancing the surface properties of biopolymers, making it an ideal candidate for manufacturing next-generation biocompatible medical devices.

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Available for download on Tuesday, August 31, 2027

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