Materials and Electro-mechanical and Biomedical Devices Based on Nanofibers

The six topics covered in the present chapter stem from recent applications of nanofibers in novel materials and devices. (i) Self-healing vascular nanotextured materials incorporate nanofibers filled with healing agents. When a material like that is damaged, the healing agents are released and polymerize spanning cracks and reparing engineering materials in situ, similarly to living tissues. (ii) Biopolymer-derived nanofibers can be formed from bio-waste, while serve in important novel biomedical and agricultural applications, as well as sophisticated filter media. The additional benefits of such nanotextured materials are in their biocompatibility and biodegradability. (iii) Nanofibers are also involved in thermo-pneumatic soft robots and actuators, which were recently developed. (iv) Biopolymer-derived nanofibers reveal significant triboelectric properties and thus, can be used as triboelectric nanogenerators. On the other hand, superhydrophobic electrospun fibrous membranes comprise an attractive venue for development of novel fabrics. (v) Nanofibers can be electroplated or sputter-coated, which leads to multiple novel applications, e.g., as nanotextured heaters, sensors, or highly effective electrostatic filters. (vi) Several additional physical properties, which can be incorporated in nanofibers include ferroelectricity, flexoelectricity and piezoelectricity, which can be employed in such devices as nanotextured wave-energy harvesters. Nanofibers can also be formed from conducting polymers and used in transparent fibrous heaters.

This chapter presents an overview of the biomedical applications of electrospun nanofibers. Due to the impact of novel technological advancements on nanoplatform fabrication, this well-explored topic is still one of the most dynamic and exciting biomedically-oriented scientific fields. The entire chapter comprises three sections dealing with different applications of nanofibers linked by a shared element, which is the vital role of the nanostructure for the functional properties of the fibrous biomaterials under discussion. The first section introduces the key contribution of electrospun nanomaterials in developing injectable biomaterials for targeted nanomedicine. The second section reviews the interaction between fibrous hemostatic agents fabricated via electrospinning and blood, starting from basic principles to the final clinical applications. The last section is entirely focused on one of the most timely topics, such as the fabrication of innovative face masks. The evolution of face mask development is discussed in order to pave the way for providing an overview of the most challenging aspect of the fabrication of the next generation of face masks characterized by multifunctionality and the possibility to activate them on demand.

This chapter is devoted to polyelectrolytes (PEs), which possess macromolecules with a substantial part comprised of ionic or ionizable functional groups. Solutions of PEs reveal non-trivial physical phenomena when such functional groups are ionized under dissociation of counterions. Accordingly, electrostatic interactions between PE charges and dissociated counterions in solution, or in complex with another PE suspended in the same electrolyte reveal unexpected and attractive properties. As a result, conformations and dynamics of such PEs in solution are significantly affected by electrostatic interactions with the other PEs of the same or an opposite polarity. Especially interesting for applications are macromolecular polyelectrolyte complexes (PECs) resulting from the association of oppositely charged PEs. Polyelectrolytes can be electrospun to form nanofibers and nanofiber membranes. Electrospinning of polyelectrolytes is described here in detail, including the unusual physical properties of the resulting nanofibers and their internal structure. The deformable polyelectrolyte fibrous membranes can sustain an electro-osmotic throughflow and serve as a key element of artificial dynamically-tunable responsive malleable surfaces of the type of those considered in Sect. 1.​3.​6 in Chap. 1.

Fluid flows coupled with electrical phenomena represent a fascinating and highly interdisciplinary scientific field. Recently, a remarkable success of electrospinning in producing polymer nanofibers has led to extensive research aimed at understanding the behavior of viscoelastic jets affected by the applied electric and aerodynamic forces, such as those imposed by the surrounding gas flows. Theoretical models have uncovered various unique aspects of the underlying physics of polymer solutions in these jets, offering valuable insights for experimental platforms. This chapter explores the progress made in the theoretical description and numerical simulations of polymer solution jets in electrospinning. It emphasizes the instability phenomena arising from both electric and hydrodynamic factors, which are pivotal for understanding the flow physics. The chapter also outlines specifications for creating accurate and computationally feasible models. Topics covered include electrohydrodynamic modeling, theories describing jet bending instability, recent advancements in Lagrangian approaches for jet flow description, strategies for dynamic refinement of simulations, and the effects of intense elongational flow on polymer networks. In addition, the present chapter discusses current challenges and future prospects in this field, which encompasses the physics of jet flows, non-trivial material properties, and the development of multiscale techniques for modeling viscoelastic jets.