COVID-19: Current challenges regarding medical healthcare supplies and their implications on the global additive manufacturing industry.

The covid-19 outbreak has caused a shortage of masks and other healthcare products for the general public around the globe. In addition, it has also affected the supply of personal protective equipment (PPE) used by healthcare services because of a sudden increase in their demand. This significant disruption in the global supply chain of these products resulted in, leaving many staff and patients without protection. The additive manufacturing (AM) industry is going through extraordinary times and can provide emergency responses to help deal with the global crisis caused by the COVID-19 pandemic. The objective of the present work is therefore to perform an up-to-date review to determine the capacity of AM to provide exclusive benefits for the medical healthcare supplies sector to fight this current situation. In this review, it is found that AM technology has proved that it can be used as a volume manufacturing technology for the ongoing crisis. However, the standardization and certification are appeared to represent the main challenges for adopting the AM in healthcare against COVID-19. Furthermore, additively manufactured materials for medical applications must be developed for medical environments. Most printed medical products for COVID-19 require biocompatibility evaluation and shall prove their ability to sterilize. Finally, this review concluded that AM technology can fulfill the requirements of face masks and ventilator parts for healthcare systems for proper controlling and treating of COVID-19 patients when the safety and efficacy of these devices are ensured.

3D Printing to Support the Shortage in Personal Protective Equipment Caused by COVID-19 Pandemic.

Currently, the emergence of a novel human coronavirus disease, named COVID-19, has become a great global public health concern causing severe respiratory tract infections in humans. Yet, there is no specific vaccine or treatment for this COVID-19 where anti-disease measures rely on preventing or slowing the transmission of infection from one person to another. In particularly, there is a growing effort to prevent or reduce transmission to frontline healthcare professionals. However, it is becoming an increasingly international concern respecting the shortage in the supply chain of critical single-use personal protective equipment (PPE). To that scope, we aim in the present work to provide a comprehensive overview of the latest 3D printing efforts against COVID-19, including professional additive manufacturing (AM) providers, makers and designers in the 3D printing community. Through this review paper, the response to several questions and inquiries regarding the following issues are addressed: technical factors connected with AM processes; recommendations for testing and characterizing medical devices that additively manufactured; AM materials that can be used for medical devices; biological concerns of final 3D printed medical parts, comprising biocompatibility, cleaning and sterility; and limitations of AM technology.

Taxonomic Importance of Pollen Morphology for Some Species of Brassicaceae.

BACKGROUND AND OBJECTIVE: Pollen morphology is one of the significant tools in solving some taxonomic problems on the family, generic or specific level and has become part of the multidisciplinary and collaborative approach in plant systematic and evolution. Therefore, this study aimed to investigate and describe the pollen morphology of 10 species belongs to 9 genera and five tribes of Brassicaceae from eastern region of Saudi Arabia by using light and scanning electron microscope. MATERIALS AND METHODS: To study the pollen morphology for ten species representing 9 genera and 5 tribes of Brassicaceae the Light Microscope (LM) and Scanning Electron Microscope (SEM). For the SEM the pollen was placed directly on brass stubs without treatment and mounted onto a metallic stub with a double-sided adhesive tape. Gold coating of few nanometers was applied using sputter coating machine (Quorum, Q150R ES, UK) to avoid charging and capture high quality images. Two statistical program; PRIMER 6, version 6.1.6 and SPSS version 16are used to fine the relationships among the studied species. RESULTS: The shape of pollen grains recorded three types; prolate, subprolate and prolate-spheroidal, the main types were prolate. The apertures were tricolpate in all studied species. Exine ornamentation of studied species recorded two types; reticulate and coarsely reticulate. The results of numerical analysis showed that species were grouped into two major clusters and each cluster divided into two groups. CONCLUSION: The results show that the morphology of pollen grains cannot be useful for taxonomical classification of the tribes but can be useful for differentiate between species belong to the same genera.

Identification of couple-stress moduli of vertebral trabecular bone based on the 3D internal architectures.

The purpose of this paper is to develop a homogeneous, orthotropic couple-stress continuum model as a substitute of the 3D periodic heterogeneous cellular solid model of vertebral trabecular bone. Vertebral trabecular bone is modeled as a porous material with an idealized periodic structure made of 3D open cubic cells, which is effectively orthotropic. The chosen architecture is based on studies of samples taken from the central part of vertebral bodies. The effective properties are obtained based on the response of the representative volume element under prescribed boundary conditions. Mixed boundary conditions comprising both traction and displacement boundary conditions are applied on the structure boundaries. In this contribution, the effective mechanical constants of the effective couple-stress continuum are deduced by an equivalent strain energy method. The characteristic lengths for bending and torsion are identified from the resulting homogenized orthotropic moduli. We conduct this study computationally using a finite element approach. Vertebral trabecular bone is modeled either as a cellular solid or as a two-phase material consisting of bone tissue (stiff phase) forming a trabecular network, and a surrounding soft tissue referring to the bone marrow present in the pores. Both the bone tissue forming the network and the pores are assumed to be homogeneous linear elastic, and isotropic media. The scale effects on the predicted couple stress moduli of these networks are investigated by varying the size of the bone specimens over which the boundary conditions are applied. The analysis using mixed boundary conditions gives results that are independent of unit cell size when computing the first couple stress tensor, while it is dependent on the cell size as to the second couple stress tensor moduli. This study provides overall guidance on how the size of the trabecular specimen influence couple stresses elastic moduli of cellular materials, with focus on bones. The developed approach is quite general and applicable to any heterogeneous cellular and composite materials.