Journal of Nanotechnology in Engineering and Medicine 

About: Journal of Nanotechnology in Engineering and Medicine is an academic journal. The journal publishes majorly in the area(s): Carbon nanotube & Nanofluid. It has an ISSN identifier of 1949-2944. Over the lifetime, 265 publications have been published receiving 3113 citations.

Solar Energy Harvesting Using Nanofluids-Based Concentrating Solar Collector

Abstract: Dispersing trace amounts of nanoparticles into the base-fluid has significant impact on the optical as well as thermo-physical properties of the base-fluid. This characteristic can be utilized in effectively capturing as well as transporting the solar radiant energy. Enhancement of the solar irradiance absorption capacity of the base fluid scales up the heat transfer rate resulting in higher & more efficient heat transfer. This paper attempts to introduce the idea of harvesting the solar radiant energy through usage of nanofluid-based concentrating parabolic solar collectors. In order to theoretically analyze the nanofluid-based concentrating parabolic solar collector (NCPSC) it has been mathematically modeled, and the governing equations have been numerically solved using finite difference technique. The results of the model were compared with the experimental results of conventional concentrating parabolic solar collectors under similar conditions. It was observed that while maintaining the same external conditions (such as ambient/inlet temperatures, wind speed, solar insolation, flow rate, concentration ratio etc.) the NCPSC has about 5–10% higher efficiency as compared to the conventional parabolic solar collector. Furthermore, some parametric studies were carried out which reflected the effect of various parameters such as solar insolation, incident angle, convective heat transfer coefficient etc. on the performance indicators such as thermal efficiency etc.Copyright © 2012 by ASME

Direct Bioprinting of Vessel-Like Tubular Microfluidic Channels

Abstract: Although great progress has been made in biofabrication of tissue constructs over the past decades, the engineered constructs still have difficulty in biomimicking the functional thick tissues or organs, due to an inefficient media exchange rate [1]. Nonhomogeneous cell distribution and limited metabolic activities are often observed, since planted cells cannot get enough oxygen, growth factors and nutrients for their metabolic activities which are needed for maturation during perfusion. Microfluidic system integration has shown great potential to alleviate current limitations. Lee and his coworkers [2] have shown great difference in cell viability with or without an embedded microfluidic channel in hydrogel scaffolds. Ling et al. [3] demonstrated that microfluidic channels are capable of delivering sufficient nutrients to encapsulated cells, and higher cell viability resulted in the region closer to the microfluidic channel. In addition, microfluidic channel systems were not only able to provide media to maintain cell metabolic activities but also to delivered signals to guide cell activities. To date, several methods have been used in microfluidic fabrication, including soft lithograph [3–5], photo-patterning [6–8], laser-based technologies [9,10], molding [11–13], and bioprinting [2,14–16]. However, due to their intrinsic characteristics, each of the above-mentioned technologies has its advantages and disadvantages. Soft lithography is the most popular method in microfluidic channel fabrication due to its low cost, accuracy, and reproducibility. Using soft lithography technology, Ling et al. [3] fabricated microfluidic cell-laden agarose hydrogel, which resulted in a significant increase in cell viability during media perfusion compared to static controls. Cuchiara et al. [4] developed a soft lithography process to fabricate a poly(ethylene glycol) diacrylate hydrogel microfluidic network. With media perfusion, encapsulated mammalian cells maintained a high viability rate in bulk hydrogel. However, soft lithograph is not a viable option for fabrication of complex three-dimensional (3D) constructs due to its cumbersome procedures. Despite their superior accuracy and repeatability, photo-patterning and laser-based methods may not be suitable for fabricating thick tissue constructs because of their limited light-penetrating depths in precursor solution. Offra et al. [6] proposed a focal laser photoablation capable of generating microstructures in transparent hydrogels. Cell behavior was successfully guided by the microchannel pattern. Molding is an inexpensive and scalable method, but complex 3D geometry is difficult to achieve and postprocedures are required after fabrication. In Ref. [12], Nazhat et al. used a molding method to incorporate unidirectionally aligned soluble phosphate-based glass fibers into dense collagen scaffolds. The diameters of the achieved microfluidic channels were around 30–40 μm, and a significant increase in cell viability was observed in the hydrogel sheets. Despite the plethora of work in microfluidic channel fabrication using the traditional methods, only a few researchers have developed strategies for bioprinting of microfluidic channels, where bioprinting can be defined as computer-controlled layer-by-layer bioadditive process enabling printing living cells precisely per predefined patterns [1]. Cell encapsulated biomaterials can be directly patterned onto substrate without any pretreating steps (such as mold or mask preparation). It offers several advantages, including precise control [16,17], automated fabrication capability [18,19], and feasibility of achieving complex shapes [15]. Zhao et al. [20] recently presented a methodology in bioprinting of perfused straight microfluidic channel structures in thick hydrogel. They created a temporary structure to form the hollow cavity which was then removed by a postprocess. In this study, a novel bioprinting fabrication process is introduced, where vessel-like microfluidic channels can be directly printed in complex shapes without any need of pre/post processes. Microfluidic channels, in the form of hollow filaments, are directly printed by a pressure-assisted robotic system using hydrogels. We performed geometric characterization of microfluidic channels through studying multiple biomaterials and their dispensing rheology. Then, microfluidic channels were embedded in bulk hydrogel to evaluate their structural integrity and media perfusion capability. Further, we examined the media transportation capability of printed and embedded microfluidic channels by perfusing oxygenized cell culture media through patterned channels. A cell viability study was carried out to access the effect of perfusion on encapsulated cells.

Scaffold-Based or Scaffold-Free Bioprinting: Competing or Complementing Approaches?

Abstract: Bioprinting is an emerging technology to fabricate artificial tissues and organs through additive manufacturing of living cells in a tissues-specific pattern by stacking them layer by layer. Two major approaches have been proposed in the literature: bioprinting cells in a scaffold matrix to support cell proliferation and growth, and bioprinting cells without using a scaffold structure. Despite great progress, particularly in scaffold-based approaches along with recent significant attempts, printing large-scale tissues and organs is still elusive. This paper demonstrates recent significant attempts in scaffold-based and scaffold-free tissue printing approaches, discusses the advantages and limitations of both approaches, and presents a conceptual framework for bioprinting of scale-up tissue by complementing the benefits of these approaches.

Nanoclay Based Composite Scaffolds for Bone Tissue Engineering Applications

Abstract: Scaffolds based on chitosan/polygalacturonic acid (ChiPgA) complex containing montmorillonite (MMT) clay modified with 5-aminovaleric acid were prepared using freezedrying technique. The MMT clay was introduced to improve mechanical properties of the scaffold. The microstructure of the scaffolds containing the modified MMT clay was influenced by the incorporation of nanoclays. The MTT assay also indicated that the number of osteoblast cells in ChiPgA scaffolds containing the modified clay was comparable to ChiPgA scaffolds containing hydroxyapatite known for its osteoconductive properties. Overall, the ChiPgA composite scaffolds were found to be biocompatible. This was also indicated by the scanning electron microscopy images of the ChiPgA composite scaffolds seeded with human osteoblast cells. Photoacoustic‐Fourier transform infrared (PA-FTIR) experiments on the ChiPgA composite scaffolds indicated formation of a polyelectrolyte complex between chitosan and polygalacturonic acid. PA-FTIR studies also showed that the MMT clay modified with 5-aminovaleric acid was successfully incorporated in the ChiPgA based scaffolds. Swelling studies on ChiPgA composite scaffolds showed the swelling ability of the scaffolds that indicated that the cells and the nutrients would be able to reach the interior parts of the scaffolds. In addition to this, the ChiPgA scaffolds exhibited porosity greater than 90% as appropriate for scaffolds used in tissue engineering studies. High porosity facilitates the nutrient transport throughout the scaffold and also plays a role in the development of adequate vasculature throughout the scaffold. Compressive mechanical tests on the scaffolds showed that the ChiPgA composite scaffolds had compressive elastic moduli in the range of 4‐6 MPa and appear to be affected by the high porosity of the scaffolds. Thus, the ChiPgA composite scaffolds containing MMT clay modified with 5-aminovaleric acid are biocompatible. Also, the ChiPgA scaffolds containing the modified MMT clay appears to satisfy some of the basic requirements of scaffolds for tissue engineering applications. DOI: 10.1115/1.4002149