Structure Formation by 3D-Printing of Cellulose from Cellulose-NMMO-Water Solutions: Analysis of Extrusion, Regeneration, and Drying Stages.

Processing cellulose from 4-methyl morpholine n-oxide (NMMO)-water solutions is a completely circular route that produces biodegradable cellulose fibers or films while recovering reusable NMMO [Guo, Y.; Cai, J.; Sun, T.; Xing, L.; Cheng, C.; Chi, K.; Xu, J.; Li, T. The purification process and side reactions in the N-methylmorpholine-N-oxide (NMMO) recovery system. Cellulose 2021, 28(12), 7609-7617]. Despite proven success in two-dimensional applications, challenges in transitioning to three-dimensional objects arise from the critical changes that cellulose undergoes during deposition, regeneration, and postregeneration stages. While emphasizing the critical diffusion-driven precipitation during regeneration, this investigation explores the influence of extrusion temperature, printing alignment, regeneration, and drying processes on interfilament fusion, bonding, shape integrity, and mechanical properties. Three distinct drying processes: ambient, vacuum, and freeze-drying were investigated. Tensile and flexural bending tests provided insight into the delamination of dried specimens. Ambient and vacuum drying enhanced the properties of specimens, while freeze-drying resulted in a more stable shape. The findings contribute to advancing the understanding of 3D-printing cellulose from NMMO solutions, addressing crucial aspects of the extrusion, regeneration, and drying stages for enhanced applications in sustainable manufacturing.

Effect of Moisture on Shape Memory Polyurethane Polymers for Extrusion-Based Additive Manufacturing.

Extrusion-based additive manufacturing (EBAM) or 3D printing is used to produce customized prototyped parts. The majority of the polymers used with EBAM show moisture sensitivity. However, moisture effects become more pronounced in polymers used for critical applications, such as biomedical stents, sensors, and actuators. The effects of moisture on the manufacturing process and the long-term performance of Shape Memory Polyurethane (SMPU) have not been fully investigated in the literature. This study focuses primarily on block-copolymer SMPUs that have two different hard/soft (h/s) segment ratios. It investigates the effect of moisture on the various properties via studying: (i) the effect of moisture trapping within these polymers and the consequences when manufacturing; (ii) and the effect on end product performance of plasticization by moisture. Results indicate that higher h/s SMPU shows higher microphase separation, which leads to an increase of moisture trapping within the polymer. Understanding moisture trapping is critical for EBAM parts due to an increase in void content and a decrease in printing quality. The results also indicate a stronger plasticizing effect on polymers with lower h/s ratio but with a more forgiving printing behavior compared to the higher h/s ratio.

EVALUATION OF VITRECTOMY AND REIMPLANTATION FOLLOWING LATE DISLOCATION OF THE INTRAOCULAR LENS-CAPSULAR BAG COMPLEX: A 3-Year Follow-up Study.

OBJECTIVES: To study the predisposition factors for dislocation of the intraocular lens (IOL)-capsular bag complex and analyze the results of subsequent reimplantation surgery. METHODS: The exclusion criteria were complicated cataract surgery and minor dislocations that appeared in the first year after cataract surgery. Thirty-six months of monitoring of the reimplantation surgery was required. The primary measurements of results were factors concerning dislocation, the interval between cataract surgery and dislocation, and postoperative complications. RESULTS: Thirty-six patients with dislocation of the capsular bag and lens were identified. Pseudoexfoliation was mentioned in 17 cases (47.2%) and was the main predisposition factor. The average interval between cataract surgery and dislocation was 11.5 years. The dislocated IOL was replaced by a posterior chamber implant in 38% of cases and an anterior chamber implant in 62%. The average best-corrected visual acuity improved significantly after the reposition surgery (P < 0.01). The average monitoring period after secondary reimplantation was 5.95 years (min. 3.03-max. 8.46). Three patients developed bullous keratopathy, all of them with an anterior chamber IOL implantation. CONCLUSION: According to our knowledge, this article is the one with the longest monitoring time to date. Pseudoexfoliation was the main risk factor for the dislocation of the IOL. Surgery significantly improved best-corrected visual acuity, and the reimplantation of the IOL in the posterior chamber was associated with less serious complications.