ABSTRACT
We investigate the compressive energy absorption performance of polymeric octet-truss lattice structures that are 3D printed using high-resolution stereolithography. These structures are potential candidates for personal protective equipment, structural, and automotive applications. Two polymeric resins (high-strength/low-ductility and moderate-strength/high-ductility) were used in this work, and a comprehensive uniaxial tensile characterization was conducted to establish an optimal UV curing time. The external octet-truss structure geometry (3â³ × 3â³ × 3â³) was maintained, and four different lattice cell densities (strut length, L) and three different strut radii (R) were printed, UV cured, and compression tested. The compressive stress-strain and energy absorption (EA) behavior were quantified, and the EA at 0.5 strain for the least dense and smallest R structure was 0.02 MJ/m3, while the highest density structure with the largest R was 1.80 MJ/m3 for Resin 2. The structural failure modes varied drastically based on resin type, and it was shown that EA and deformation behavior were related to L, R, and the structures' relative density (ρ¯). For the ductile resin, an empirical model was developed to predict the EA vs. compressive strain curves based on L and R. This model can be used to design an octet-truss lattice structure based on the EA requirements of an application.
ABSTRACT
OBJECTIVE: To evaluate the performance of an endoscopic 3-mm electrothermal bipolar vessel sealing device (EBVS) intended for single use after multiple use-and-resterilization cycles. STUDY DESIGN: Ex vivo study. SAMPLE POPULATION: Eight 3-mm EBVS handpieces. METHODS: Handpieces were subjected to a maximum of 15 cycles of testing, including simulated surgery, sealing and burst pressure testing of porcine carotid arteries, reprocessing, and hydrogen peroxide plasma resterilization. Failure was defined as two sequential vascular seal leakage events occurring at <250 mm Hg. Histological evaluation, maximum external temperature of the jaws, sealing time, tissue adherence, jaw surface characterization, and mechanical deterioration were studied. Failure rate was analyzed by using a Kaplan-Meier curve. Linear and ordinal logistic mixed models were used to analyze sealing time, handpiece jaw temperature, and adherence score. RESULTS: Mean ± SD diameter of arteries was 3.22 ± 0.35 mm. Failure was observed starting at cycle 10 and going up to cycle 13 in 37.5% (3/8) of the handpieces. Tissue adherence increased after each cycle (P < .001). Maximum external temperature (79.8°C ± 13.9°C) and sealing time (1.8 ± 0.5 seconds) were not significantly different throughout cycles up to failure. A flatter surface and large scratches were observed microscopically throughout the jaw surface after repeated use and resterilization. CONCLUSION: The 3-mm EBVS handpiece evaluated in this study can be considered safe to use for up to nine reuse-and-resterilization cycles. CLINICAL SIGNIFICANCE: These data provide the basis for establishing preliminary guidelines for the reuse and hydrogen peroxide plasma resterilization of an endoscopic 3-mm EBVS handpiece.
