Failure mechanisms in fibrous scaffolds.

Polymeric fibrous scaffolds have been considered as replacements for load-bearing soft tissues, because of their ability to mimic the microstructure of natural tissues. Poor toughness of fibrous materials results in failure, which is an issue of importance to both engineering and medical practice. The toughness of fibrous materials depends on the ability of the microstructure to develop toughening mechanisms. However, such toughening mechanisms are still not well understood, because the detailed evolution at the microscopic level is difficult to visualize. A novel and simple method was developed, namely, a sample-taping technique, to examine the detailed failure mechanisms of fibrous microstructures. This technique was compared with in situ fracture testing by scanning electron microscopy. Examination of three types of fibrous networks showed that two different failure modes occurred in fibrous scaffolds. For brittle cracking in gelatin electrospun scaffolds, the random network morphology around the crack tip remained during crack propagation. For ductile failure in polycaprolactone electrospun scaffolds and nonwoven fabrics, the random network deformed via fiber rearrangement, and a large number of fiber bundles formed across the region in front of the notch tip. These fiber bundles not only accommodated mechanical strain, but also resisted crack propagation and thus toughened the fibrous scaffolds. Such understanding provides insight for the production of fibrous materials with enhanced toughness.

Failure mechanisms in fibrous scaffolds

Polymeric fibrous scaffolds have been considered as replacements for load-bearing soft tissues, because of their ability to mimic the microstructure of natural tissues. Poor toughness of fibrous materials results in failure, which is an issue of importance to both engineering and medical practice. The toughness of fibrous materials depends on the ability of the microstructure to develop toughening mechanisms. However, such toughening mechanisms are still not well understood, because the detailed evolution at the microscopic level is difficult to visualize. A novel and simple method was developed, namely, a sample-taping technique, to examine the detailed failure mechanisms of fibrous microstructures. This technique was compared with in situ fracture testing by scanning electron microscopy. Examination of three types of fibrous networks showed that two different failure modes occurred in fibrous scaffolds. For brittle cracking in gelatin electrospun scaffolds, the random network morphology around the crack tip remained during crack propagation. For ductile failure in polycaprolactone electrospun scaffolds and nonwoven fabrics, the random network deformed via fiber rearrangement, and a large number of fiber bundles formed across the region in front of the notch tip. These fiber bundles not only accommodated mechanical strain, but also resisted crack propagation and thus toughened the fibrous scaffolds. Such understanding provides insight for the production of fibrous materials with enhanced toughness. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Stakeholder challenges in purchasing medical devices for patient safety.

OBJECTIVE: This study identifies the stakeholders who have a role in medical device purchasing within the wider system of health-care delivery and reports on their particular challenges to promote patient safety during purchasing decisions. METHODS: Data was collected through observational work, participatory workshops, and semi-structured qualitative interviews, which were analyzed and coded. The study takes a systems-based and engineering design approach to the study. Five hospitals took part in this study, and the participants included maintenance, training, clinical end-users, finance, and risk departments. RESULTS: The main stakeholders for purchasing were identified to be staff from clinical engineering (Maintenance), device users (Clinical), device trainers (Training), and clinical governance for analyzing incidents involving devices (Risk). These stakeholders display varied characteristics in terms of interpretation of their own roles, competencies for selecting devices, awareness and use of resources for purchasing devices, and attitudes toward the purchasing process. The role of "clinical engineering" is seen by these stakeholders to be critical in mediating between training, technical, and financial stakeholders but not always recognized in practice. CONCLUSIONS: The findings show that many device purchasing decisions are tackled in isolation, which is not optimal for decisions requiring knowledge that is currently distributed among different people within different departments. The challenges expressed relate to the wider system of care and equipment management, calling for a more systemic view of purchasing for medical devices.