Micro and Nanomanufacturing Volume II

With many thousands of different varieties to date, the nanowire (NW) library continues to grow at pace. With the continued and hastened maturity of nanotechnology, significant advances in materials science have allowed for the rational synthesis of a myriad of NW types of unique electronic and optical properties, allowing for the realisation of a wealth of novel devices, whose use is touted to become increasingly central in a number of emerging technologies. Nanowires, structures defined as having diameters between 1 and 100 nm, provide length scales at which a variety of inherent and unique physical effects come to the fore [1], phenomena which are often size suppressed in their bulk counterparts [2–4]. It is these size-dependent effects that have underpinned the growing interest in the growth and fabrication, at ever more commercial scales, of nanoscale structures. Nevertheless, many of the intrinsic properties of such NWs become largely smeared and often entirely lost when they adopt disordered ensembles. Conversely, ordered and aligned NWs have been shown to retain many such properties, alongside proffering various new properties that manifest on the micro- and even macroscale that would hitherto not occur in their disordered counterparts.

Taxanes including paclitaxel and docetaxel are highly active against many types of cancers. The main obstacle with developing delivery systems of taxanes is their poor water solubility. In this chapter, taxanes were reviewed in terms of their pharmacology, solubility and stability using traditional formulations such as those based on using Cremophor EL and novel nanocarrier-based formulations including liposome, nanoparticle and polymeric micelle delivery systems. Commercially available formulations of paclitaxel such as Taxol, Abraxane and Genexol-PM were highlighted.

Nanotechnology is the application and manipulation of structures, typically particles or molecules within the ‘nano’ range (one billionth of a metre (nm)). Nanoparticles measure 100 nm or less and have a greater surface area to weight ratio, meaning they can alter the properties of many conventional materials. Nanoparticles can be used in conjugation with traditional materials or to create novel structures with unique electrical, chemical and mechanical properties. These natural and artificial nanostructures offer new approaches to the management of disease; from diagnostics to treatment and preventative applications. These include advances in targeted drug delivery, repair mechanisms and healing, antimicrobial coats on implant surfaces, osteointegration of implants and the use of nanoscaffolds for tissue integration and regeneration. This chapter examines current concepts in nanomedicine and the potential applications of nanotechnology in the field of orthopaedics with a particular focus on surgery of the knee.

This chapter presents some of the most important currently utilised techniques for the characterisation of nanostructures and nanoparticles. The techniques presented here are grouped into categories of topology, internal structure and compositional investigation. Topological techniques presented here include field emission scanning electron microscopy (FESEM), scanning probe microscopy (SPM), optical microscopy (confocal and NSOM) and particle size distribution with dynamic light scattering (DLS). Internal structure techniques presented include transmission electron microscope (TEM), magnetic resonance force microscope (MRFM) and X-ray diffraction (XRD). Compositional techniques presented include X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), secondary ion mass spectroscopy (SIMS) and Auger electron spectroscopy (AES). To highlight the current capabilities and applications of these techniques, case studies from recent literature are presented.

Semiconductor photocatalysis is an emerging field in materials science due to its applications in solar energy conversion and environment remediation. Currently, most efficiently and conventionally studied semiconductor materials for photocatalysis are TiO₂, ZnO, ZnS, CdS, WO₃, Fe₂O₃, and Bi₂WO₄ [1, 2]. Among all these, titanium dioxide (TiO₂) is the most widely used photocatalyst due to its excellent properties, such as high stability in the aqueous media, low cost, relatively low toxicity, and excellent photocatalytic performance for the degradation of organic pollutants. In photocatalysis process, when a semiconductor is irradiated with photons of energy (hν) that is equal to or higher than the semiconductor band gap energy (hν ≥ E _g), these photons are absorbed by the semiconductor and create high energy electron–hole pairs. The photogenerated electrons and holes that migrate to the surface of the semiconductor without recombination can reduce and oxidize the reactants adsorbed on the semiconductor surface, respectively [3]. Therefore, suppressing the recombination of photogenerated electron–hole pairs and the efficient utilization of visible light are some of the main challenges before making these processes economically feasible [4, 5]. In order to overcome these drawbacks, previously, a lot of approaches have been explored to improve the photocatalytic performance of TiO₂ under visible light irradiation. These approaches include doping with metal and nonmetal ions, dye sensitizing, compositing of TiO₂ with narrow band gap semiconductor, etc. [6–17].

In the last 20 years, computational chemistry has become a very important research methodology in all areas of nanoscience. Computer simulations are powerful nano-scopes that can to reveal details of molecular processes on lengths of space and time unreachable to experimental observations. Along clarifying the physicochemical properties of single molecules or systems, they provide insights for helping designing and manufacturing of new nanomaterials and nanodevices. Among the various computational methods, Molecular Dynamics simulation is a powerful approach to analyze both structural and dynamic properties ones at the different scale of time and space. This chapter aims to provide a general and concise introduction to the MD simulations of molecular systems by showing some example of applications to the study of biological macromolecules and nanomaterials.

The goal of the research presented in this chapter is to study and develop an alternative methodology to produce painted chrome-plated polymer parts required by the automotive industry. Nowadays the automotive industry is substituting metal parts for plastic ones. However, these new plastic parts must detain the aesthetic and the main properties of the metal components, i.e. the metallic appearance is of utmost importance, as well as the “cold sensation” of metal.

Binnig et al. invented atomic force microscope (AFM) in 1986. It is a scanning tool for nanostructure investigations. It is now considered to be one of the landmarks of modern sciences, for citations of the first article increase more than 13,500 times [1]. The AFM has come up as a new addition to macroscopic and microscopic techniques since it has benefits in sample preparation and the ability of high-resolution imaging in both liquid and air environment if compared to standard light microscopy techniques. This sophisticated instrument has successfully been used in all branches of science like material science [2], food science [3], nanofabrication [4], and microbiology, for nearly two decades after its invention [5]. The microbiology field has been revolutionized by AFM. It has enriched the realm of sample preparation and microbial surface analysis in particular during the last two decades [6].

The invention of silicon (Si)-based diodes and especially the Si bipolar transistors by Shockley, Bardeen, and Brattain seven decades ago has triggered the era of fast-growing information and computer technologies. As a consequence, the development into microelectronic fabrication technologies has also been extensively investigated and progressed to reduce device size and to increase the integration, as well as to enhance their performance. The growing rate of the state-of-the-art microprocessors has reached above Moore’s law, which states that the number of transistors on a chip doubles roughly every 2 years. This achievement is largely attributed to the advanced micro- and nanofabrication processing [1].

Cellular discrimination and detection in a biological fluid, e.g., blood, play a critical role in identifying any abnormalities. It can then lead to early diagnosis of many diseases. Micropores and nanopores have been effectively used for biodetection applications. Cell discrimination with micropores basically uses the characteristic properties of the cells like size, structure (cytoskeleton), behavior, surface charge, etc. A review of the micropore techniques used for cancer cell detection is presented here. Fabrication challenges of solid-state micropores are also discussed.

Fool’s gold or Iron pyrite (FeS₂) is a semiconductor comprised of earth-abundant elements that has the potential to be a low cost photovoltaic material with comparatively low toxicity. Despite its promise, photovoltaic modules containing FeS₂ continue to show small photo-voltages which have limited power conversion efficiencies to around 3%. Bandgap engineering of pyrite by doping may help in increasing power conversion efficiency by increasing the portion of the solar spectrum absorbed. This may lead to the prospect of tandem device architectures that utilise pyrite as an intrinsic semiconductor

This chapter shadows the characteristics of iron pyrite as promising photovoltaic material. It elaborates the properties of iron pyrite (FeS₂) and transition metal doped iron pyrite thin films fabricated by various physical and chemical deposition methods primarily via aerosol-assisted chemical vapour deposition (AACVD). At the end, this chapter provides a brief summary for the current status of pyrite to be used as cheap inexpensive photovoltaic material.

Over the past few years, focus on the clinical application of nanobiomaterials in dentistry has been an area of interest to researchers worldwide. Nanotechnology is currently driving dental materials industry to substantial growth [1]. The advent of nanotechnology in dentistry seems to have answers to the mysteries or problems associated with conventional materials, as they have the tendency to mimic surface and interface properties of natural tissues. Nanotechnology has as a principle the ambitious challenge of precisely controlling individual particles in nanometer range. Some of the results are very relevant and have a major impact on human life and have already been adapted [2]. While the fields of tissue engineering and regenerative medicine have hinted at much promise over the last few decades, significant amount of research is still required with the field of nanotechnology to innovate new exciting materials that can overcome drawbacks of the existing biomaterials. Nanodentistry is still considered as an emerging field with a huge potential to yield new innovative generation of technologically advanced biomaterials in prosthodontics, orthodontics, periodontics, operatives, or restorative dental sciences. It is expected that nanodentistry will eventually give rise to highly efficient, effective, and personalized dental treatment [2].

Diamond and its thin films have acquired an amazing charm and large potential industrial applications because of their highly valuable characteristics such as high-carrier mobility and large energy gap making them good insulators with high thermal conductivity. Moreover, doping of various elements such as boron, nitrogen, oxygen, and phosphorus in diamond further enhances its usefulness into applications of electronics and electrochemical devices. Such interesting characteristics have significantly attracted the attention of researchers and opened new ways for handling conductivity issues caused by impurity-induced metallization in diamonds. That’s why present study on the characterization of diamond thin films under various conditions/morphologies has been performed and divided into two parts: Experimental work as well as computational calculations based on density functional theory (DFT) using pseudo-potential method involving spin-polarized GGA-PW91 functionals on plane wave basis sets using VASP codes.

Micro- and nanocrystalline diamond films have been deposited on silicon (1 0 0) wafers using hot filament chemical vapor deposition method using source gases (CH₄ + H₂) as well as by doping different elements like boron, oxygen, and nitrogen under different deposition conditions involving chamber pressure, doping concentration, and gas flow rate. These films have been characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and van der Pauw technique to measure and analyze structure, crystal quality, morphology, and electrical resistivity of the deposited diamond films.

Results have shown that diamond growth rate decreases at low methane concentrations but increases (~3 orders) at high methane content in the deposition chamber. It also decreases on increasing chamber pressure, showing improvement in the quality of diamond crystals. The optimum CH₄ content for well-faceted crystals is 3.0 mL/min with minimum resistivity of 1.79 × 10⁷ Ω cm. Effect of doping on diamond characteristics demonstrates that as concentration of O₂ or B increases, high-quality large-sized {1 1 1} grains are deposited yielding low resistivity (~10⁵ Ω cm). However, such good-quality micro-diamond grains are noticed at low N₂ concentrations. In addition, superposition of both nano- and micro-sized grains is observed at higher N₂ content. Resistivity of such films decreased significantly to 10⁷ Ω cm due to increased sp² bonds.

Theoretical aspects of doped diamond films demonstrate that both O₂ and B-atoms support the splitting of diamond energy band by forming impurity states near/at Fermi level and hence enhance conductivities of these thin films; this fact supports our experimental results of doped diamond films. Moreover high doping concentration affects significantly on atomic charge making it positive (1.89 eV). On the other hand, transition metal (TM) dopants become spin polarized by magnetizing p electrons of C-atoms through p-d hybridization. Such hybridization is strong for Cu doping as compared to other TM dopants and involves FM coupling state rather than AFM. The appearance of specific O (2p) band at −18 eV in the energy band spectrum of O-doped diamond signifies the existence of donor levels between valence and conduction bands which were very deep and lead to reduction of the energy gap (~0.865 eV). However, the incorporation of oxygen atoms into the diamond (1 0 0) surface was partially favorable.

The idea of using magnetic nanomaterials in biomedical applications has been studied since last decades. Magnetic nanomaterials have been found as a promising candidate in biological applications. This chapter presented the diverse approach to engineer the nanoparticles for targeted applications. Superparamagnetic iron oxide nanoparticle (SPION) cores of 10–25 nm were synthesised using co-precipitation method iron (II) and iron (III) salts in alkaline medium. The superparamagnetic behaviour is an ideal solid support for the hyperthermia ablation and magnetic field-triggered stimuli for drug release. These cores were further coated with mesoporous silica rendering them versatile materials, which can enhance the stability, drug-loading capacity and its release in controllable manner. Moreover, their promising applications as magnetic field-triggered hyperthermia ablation and magnetic field-triggered controlled-release drug delivery combining both thermos-chemotherapy system.

These materials were characterised using a variety of techniques such as Zetasizer, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) analysis, transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM) and magnetic field-induced hyperthermia. The diameter of spherical superparamagnetic iron oxide nanoparticles was measured to be from 10 to 255 nm. Crystalline magnetite (Fe₃O₄) structures were confirmed by powder XRD. These magnetite nanocrystals were further modified with a biocompatible silica shell. Brunauer-Emmett-Teller (BET) analysis revealed a mesoporous shell structure. VSM of core-shell composite materials depicted superparamagnetic nature; hence, these materials have the ability to heat over the exposure to an applied external magnetic field for hyperthermia ablation.

Anticancer drug (doxorubicin, DOX) loading and release profile of bare spherical and silica-coated spheres were studied for potential therapeutic application. Exposure to AC magnetic field (200 G, 406 kHz), the SPION materials generated hyperthermia in a time-dependent manner reaching 50 °C in 3 min. Magnetic field-triggered drug release was seen only in spherical core-shell nanocomposites with 6X higher compared at 37 °C without exposure.

Due to their compact design, ease of manufacture and high efficiency in heat and mass transfer, helically coiled tubes are widely used in a number of industries and processes such as in the food, nuclear, aerospace and power generation industries and in heat recovery, refrigeration, space heating and air-conditioning processes. Due to the formation of a secondary flow, which inherently enhances the mixing of the fluid, helically coiled tubes are known to yield enhanced heat transfer characteristics when compared to straight tube heat exchangers. The secondary flow is perpendicular to the axial fluid direction and reduces the thickness of the thermal boundary layer. Goering et al. [1] estimated the secondary flow to account for circa 16–20% of the mean fluid flow velocity.

In the new era of medicine, 3D printing technique in pharmaceutical manufacturing has already yielded success. For example, Aprecia^®, an FDA-approved pharmaceutical company, has launched its first approved product which is not only unique because of a novel manufacturing process but also better than conventional compressed tablets. 3D printing is an inexpensive additive manufacturing technique that builds a 3D object by successive layering on top of each other in a 2D fashion. The layering of the object in process is controlled digitally in a computer-aided design (CAD). 3D printing of pharmaceuticals suits best for personalised therapy, not only in case of doses but dosage form as well. A personalised dosage form can be designed and printed in such a way that the drugs are combined in a single pill (polypill). This cannot only make the therapy and schedule convenient for patient but also increase adherence.

As a background to this book chapter, the thermal hydraulic properties of fluids in microchannels have been reviewed. Figure 17.1 (Qu and Mudawar) [1] is an electronic component on top of a microchannel heat sink.

The practice of joining blood vessels has been ongoing since the late nineteenth century, although it was initially restricted to animal studies and experimental techniques. At this time, fine silk thread and curved needles had been introduced [1], which was a significant advancement on previous suture materials such as leather, tendon, and catgut [2], although these were used for wound closure rather than vascular repair. It was not until the mid-twentieth century, circa World War II, that vascular anastomoses were performed whilst repairing or reconstructing traumatic injuries [3]. The natural progression from repairing vascular injuries was to perform these procedures in smaller and smaller vessels. Of course, this necessitated use of an operating microscope and development and manufacture of finer suture materials, needles, and more delicate instruments.