Out-of-plane auxetic nonwoven as a designer meta-biomaterial

Biomaterials are porous and three-dimensional (3D) templates, which are used as biological substitutes in tissue engineering. Targeting the optimal design of biomaterials requires a synergy between mechanical, porous, mass transport, and biological properties. To address this challenge, we propose a non-periodic meta-biomaterial in the form of an out-of-plane auxetic nonwoven scaffold that possesses a 3D interconnected highly porous structure with remarkable mechanical properties corresponding to conventional nonwoven material. A design strategy of utilizing larger fiber diameters to enhance the porosity and permeability characteristics successfully devised the nonwoven scaffold with an extraordinary out-of-plane auxetic effect. In situ tensile-X-ray microcomputed to-mography (microCT) analysis has been carried out to monitor the variation in the morphological characteristics.IndoHungarian Joint Research project [INT/HUN/P-18/2017 (2017-2.3.7-TET-IN-2017-00008)]; NKFIHNational Research, Development & Innovation Office (NRDIO) - Hungary [GINOP-2.3.3-15-2016-00010]; HAS Janos Bolyai fellowshipThe authors gratefully acknowledge the financial support by IndoHungarian Joint Research project no. INT/HUN/P-18/2017 (2017-2.3.7-TET-IN-2017-00008). The NKFIH GINOP-2.3.3-15-2016-00010 project and HAS Janos Bolyai fellowship (D.S.) are also acknowledged

Metastable wetting model of electrospun mats with wrinkled fibers

Electrospun mats with targeted wettability are a way forward to diversify their mainstream applications and can facilitate in creating a platform for a remarkable set of properties. Limited control over the fiber morphology and surface chemistry, along with the complex architecture of electrospun mats, pose some of the key challenges for maneuvering the wettability. Herein, we present the design principles that underpin the key determinants responsible for a metastable state of a water droplet on electrospun mats possessing wrinkled surface topography. A 'first-of-its-kind' analytical model of apparent contact angle based on the modified Cassie-Baxter state has been proposed that accounts for the dual-scale roughness originating from fiber wrinkles and protuberances created by fiber-fiber contacts. Three-dimensional (3D) fiber and structural parameters obtained via X-ray microcomputed tomography (microCT) analysis served as key inputs for predictive modeling. The analytical model of the apparent advancing and receding contact angles has been validated with electrospun mats having well-defined orientation characteristics. In general, the theory and experiments are in reasonable agreement. Although similar magnitudes of static and advancing contact angles of water on surfaces of randomly and aligned electrospun mats have been experimentally observed, the receding contact angles differed significantly

A combinatorial approach to the elastic response of electrospun mats: Architectural framework and single fiber properties

Electrospun is a unique class of porous and heterogeneous materials with multi-length-scales constituents that offer a rich variety of surface functionalities to serve a host of applications. Upscaling the electrospun materials from the laboratory to the industry is often limited by the lack of understanding of their mechanical properties. Herein, we developed a theoretical framework to predict the elastic constants of the electrospun mats that hinges on the concept of elastic properties of constituent fibers, three-dimensional (3D) alignment of fibers, and local fiber curvature. Enabled by continuum-based micromechanical approaches, this framework successfully pre-dicted the elastic moduli regardless of bead-string morphology and local architectural heterogeneities present within the electrospun mats. The 3D fiber orientation distribution obtained using X-ray nano-computed tomography (nanoCT) analysis served as a key input for the validation of the analytical model. In general, the predicted elastic moduli are in reasonably good agreement with the experimental data of randomly oriented and preferentially aligned polylactic acid (PLA)-based electrospun mats. To demonstrate our analytical model's versatility and reliability, another set of PA6(3)-based electrospun mats has been chosen from the literature for validation purposes. The parametric analysis has been performed to provide a roadmap to improve the elastic moduli of electrospun mats and justify the assumed values of some of the key attributes