Nano/Micro-Structured Materials for Energy and Biomedical Applications

In response to the need for high energy density and low-loss film capacitors in various electrical and power applications, polymer nanocomposite dielectrics or nanodielectrics have attracted substantial attention in recent years. The idea is to combine the high dielectric constant property from inorganic nanoparticles and the high breakdown strength and low-loss properties from the polymer matrices. Both theoretical and experimental studies have carried out to testify this idea. In this chapter, we review both theoretical and experimental achievements and fundamental understanding on this topic. In particular, we focus on the dielectric loss mechanisms in polymer nanodielectrics. It is found that high permittivity contrast between the nanofillers and the polymer matrices tends to decrease the dielectric breakdown strength because of nonuniform electric field distribution. High conductivity contrast between ceramic nanofillers and the polymer matrix will induce internal electronic conduction loss. For polymer/metallic nanoparticle dielectrics, field electron emission from metallic nanoparticles under a high field tends to increase the electronic conduction and thus decrease the dielectric breakdown strength. In the future, research should focus on mitigating these dielectric loss mechanisms in order to achieve viable polymer nanodielectrics for film capacitor applications.

Recently, there has been an increasing interest in multiferroic compounds owing to the coexistence of different ferroic order parameters, suggesting great commercial and technological potential. Compared to composites which exhibit multiferroic properties due to synergistic coupling effects between different components, single-phase multiferroic materials exhibiting the magnetoelectric effect (ME) have attracted much attention because of their special crystal structure that contributes to ME, thereby offering promising potential for applications in spintronic devices. This chapter will provide an extensive discussion on single-phase ME materials with specific focus centered on various categories of ME materials based on their different mechanisms. The physical principles of ferromagnetism (FM), ferroelectricity (FE), and ME effects as a result of coupling interactions between FM and FE are first discussed in Sect. 2. Section 3 mainly concentrates on distinct types of single-phase ME materials with different underlying ME mechanisms. Section 4 provides a summary and perspective on future developments in the synthesis of a wide range of magnetoelectric materials.

Fiber-based materials have been used in a wide range of applications, from textiles to biofunctional scaffolds, and research on these materials continues to yield new and exciting results. In the past decades, electrospinning has been shown to be a particularly versatile and adaptable method of fiber formation. A great number of variables in the electrospinning process can be finely tuned to alter the resultant properties of the electrospun materials. Among all published research on electrospinning, poly(ε-caprolactone) (PCL)-based electrospun fibers have been most intensively studied due to the low cost, good processability, great biocompatibility, and biodegradability of PCL. This chapter highlights the current advances in electrospun PCL-based materials by categorizing these materials into following six groups: (1) PCL-natural biopolymer-based material, (2) PCL blended with other biodegradable synthetic polymers, (3) PCL blended with other synthetic polymers, (4) PCL fibers functionalization utilizing bioactive molecules, (5) PCL-based composites with inorganics or other nanofillers, and (6) PCL fiber with post-electrospinning decoration. We also summarize the fabrication techniques, experimental parameters, as well as the structure, morphology, and physicochemical properties of these fiber products. This chapter provides a comprehensive review of fabricating various PCL-based electrospun materials and their potential applications as biodegradable and biocompatible materials, such as biomedical implants, tissue scaffolds, drug carriers, gene delivery vehicles.

In our study, “green” nanoparticle synthesis has been achieved using environmentally acceptable solvent system and eco-friendly agents. A mild, versatile, and controlled methodology was used to form biomorphic mineralization-mediated self-assembly nanonoble metal materials, and their activities were explored. The work lays the groundwork for developing biotemplated nanomaterials that can be used as building block for the creation of nanomaterials. Meanwhile, the Au and Pt nanomaterials have great application prospects.

The template method is one of the most commonly used techniques to fabricate polymer nanostructures. Polymers can be introduced into the nanopores of porous templates via various template wetting methods. In recent years, there have been significant progresses in the fabrication and characterization of polymer nanostructures using the template method. Here, we first introduce porous templates and the basic concept of the template wetting method. The anodic aluminum oxide (AAO) template, one of the most commonly used porous templates, will be discussed in more detail. We then cover some of the most important template wetting methods used for polymer materials, such as the melt wetting method, the microwave annealing wetting method, and the solution wetting method. Additionally, some of the newly developed wetting methods such as the nonsolvent-induced solution wetting method and the solvent annealing wetting method are described. By applying these methods, different types of polymers can be infiltrated into the nanopores, such as homopolymers, polymer blends, block copolymers, and polymer/inorganic hybrid materials. Some recent works on the fabrication of porous polymer nanostructures using templates are also summarized. Finally, recent studies on the morphology changes of the polymer nanostructures driven by the Rayleigh-instability transformation are reviewed.

Peptide-based organogels/hydrogels are flexible and versatile in biological and nanotechnological applications. These supramolecular gels consisted of supramolecular fibrous networks formed through non-covalent interactions, including hydrogen bonding, hydrophobic, electrostatic, π–π stacking, and van der Waals interactions. In this chapter, we present the assembly, structures, and governing interactions of these supramolecular gels based on a broad range of peptides. We also highlight the potential applications of these supramolecular gels in tissue engineering, drug delivery, templates for nanofabrication, and detergent of waste water, etc.

With unique structure and characteristics, graphene has become one of the most intensively explored carbon allotropes in materials science and accompanied by increasing research interest for drug delivery applications. In addition, phototherapy is a kind of medical treatment with light utilization for treating diseases such as cancers and peripheral infections. This chapter shows an extensive overview of the main principles and the recent strategies about fabricating various self-assembling graphene-based nanocomposites and nanomaterials toward photodynamic therapy applications. The up-to-date advances for multicomponent complexed graphene composites with drug molecules are also reviewed. Finally, challenges and outlooks in materials development for photodynamic therapy applications and drug delivery are suggested.

Over the past thirty years, interest in how mammalian cells interact with materials has exploded, with applications ranging from diagnostic in vitro testing, to bioprocess engineering with microcarriers, and to tissue engineering. This interest has paralleled a revolution in material processing methods which allow scientists and engineers to create an enormous variety of micro- and nanotopological features. By studying aspects of cell behavior such as gene expression, viability, motility, and fate when cells are presented with simple architectural elements, biomedical engineers hope to build a toolbox of topological features that can be deployed to solve specific tissue engineering problems. In this chapter, we first discuss fundamental molecular biology-based mechanisms behind cell–material interactions and then focus specifically on mammalian cell interactions with nanofibers, nanofibrous microspheres, nanogrooves, nanopits, nanotubes, and nanopillars, along with their applications in tissue engineering.