Review: Auxetic Polymer-Based Mechanical Metamaterials for Biomedical Applications.

Over the last three decades but more particularly during the last 5 years, auxetic mechanical metamaterials constructed from precisely architected polymer-based materials have attracted considerable attention due to their fascinating mechanical properties. These materials present a negative Poisson's ratio and therefore unusual mechanical behavior, which has resulted in enhanced static modulus, energy adsorption, and shear resistance, as compared with the bulk properties of polymers. Novel advanced polymer processing and fabrication techniques, and in particular additive manufacturing, allow one to design complex and customizable polymer architectures that are particularly relevant to fabricate auxetic mechanical metamaterials. Although these metamaterials exhibit exotic mechanical properties with potential applications in several engineering fields, biomedical applications seem to be one of the most relevant with a growing number of articles published over recent years. As a result, special focus is needed to understand the potential of these structures and foster theoretical and experimental investigations on the potential benefits of the unusual mechanical properties of these materials on the way to high performance biomedical applications. The present Review provides up to date information on the recent progress of polymer-based auxetic mechanical metamaterials mainly fabricated using additive manufacturing methods with a special focus toward biomedical applications including tissue engineering as well as medical devices including stents and sensors.

Bi-model cationic dye adsorption by native and surface-modified Trichoderma asperellum BPL MBT1 biomass: From fermentation waste to value-added biosorbent.

In this study, we aimed to assess the possible reusability of native and surface-modified waste biomass of a novel ascomycetes fungi Trichoderma asperellum BPL MBT1 for the adsorption of triphenylmethane dyes. Spent biomass obtained from fermentation medium has been applied in the uptake of model cationic dyes viz., crystal violet and malachite green. Optimization of experimental parameters by batch mode studies revealed that dye adsorption is influenced by medium pH time, initial concentration of dyes, and adsorbent dosage. It was observed that pH 10 was optimum for cationic dye adsorption. Further, the adsorption process obeyed the bi-model (Langmuir-Freundlich model) isotherm and adhered to pseudo-second-order kinetics. The involvement of ion exchange as the dominant mechanism of dye adsorption was indicated by the mean free energy obtained from Dubinin-Radushkevich isotherm. Cellular morphology and the involved functional groups were studied by scanning electron microscopy and Fourier transform infrared spectroscopy that revealed the presence of carbon and oxygen containing groups on the surface. Maximum desorption efficiency was achieved using a 0.1 M solution of HCl and the stability of the biosorbent was confirmed through reusability analysis. Our results confirm the applicability of both native and surface-modified T. asperellum BPL MBT1 biomass as a potential biosorbent for the sustainable wastewater treatment and safe dye disposal.