Narrow Results

Conductive and transparent thin film structures are useful in flexible electronics. In this paper, we report multi-walled carbon nanotubes (MWCNTs) patterning into gradient regular patterns with large area of about several square centimeters on silicon or wafer glass slide via thermally enhanced evaporative self-assembly under wedge-shaped geometric confinement. The morphologies, electrical and optical properties of the MWCNTs thin film were characterized. The findings reveal that the conductance would increase with depositing times, meanwhile the transparency would decrease. The resistance of the grid patterning films of MWCNTs has a nearly linear relation to the transmittance in a relatively large range. The MWCNTs can be easily transferred to flexible substrate such as PET films or an adhesive tape. In comparison, SWCNTs could hardly be deposited into stripes or grid patterns, but the continuous thick films and discontinuous thin films could demonstrate better electrical and mechanical performance.

Butterfly-shaped features (with sizes from about 6 to 90 μm) were found on the surface of a shape-memory polymer (SMP) after a process of 50% stretching, slightly polishing, and then heating for shape recovery. We identified the underline mechanism, which is evidenced by the switching of butterflies by 90° from the previous direction after stretching. The case discussed here demonstrates the feasibility of using SMPs for patterning up to nanoscale for different shapes.

In recent times, among all the substrates used in microfluidic systems, cellulose paper is used as a handy, low-cost substrate that has gained attention for carrying fluid on its surface over capillary pressure. Cellulose paper substrate has exhibited great potential on microfluidic devices owing to prevalent obtainability, easy fluid (sample) flow system, flexibility, and low cost. Cellulose paper is fibrous, biocompatible, and hydrophilic in nature due to the hydroxyl group of the cellulose molecule. Based on the dominance of functional hydroxyl groups, cellulose is very reactive and every single cellulose fiber acts like a microchannel on the paper substrates. Aggregation of inter- and intra-cellulose fiber chains has a strong binding affinity to it and toward materials containing hydroxyls groups. In this paper, impact of inter- and intra-cellulose fiber on the paper substrate has been discussed through an experimental study. For the addition of work a “hydrophobic penetration-on-paper substrate (Hyp-POP)” method has been shown by using TiO₂ ink as a hydrophobic material to design the microfluidic channel on the Whatman cellulose filter paper (grade 1) as a paper substrate. In this experimental study, the intra-cellulose fibers of paper substrate interact through hydrogen bonds with water molecules and form a hydrophilic surface on paper substrate while TiO₂ binds with intra-cellulose fibers by electrostatic forces which change the crystallinity of intra-cellulose fiber and make the surface of paper substrate; hydrophobic. Field Emission Scanning Electron Microscope (FESEM) analysis is conceded for microfluidic channel analysis on the paper surface and EDS is carried out for TiO₂ ink contents analysis. It has been experimentally observed that the printing material of TiO₂ ink with 17.2% Ti content is suitable to integrate hydrophobic barrier on paper substrate for microfluidic channel fabrication. The wetting ability of Whatman cellulose filter paper (grade 1) was further evaluated by contact angle measurements (Data physics OCA 15EC). Using “Hyp-POP” method a hydrophobic pattern (width 3140 $\mu$m) on paper substrate has been made for the flow of liquid (blue fountain ink) into a paper fluidic channel (width 1860 $\mu$m) without any leakage.

In order to create suitable nanoholes for quantum dot (QD) localization on InP and GaAs surfaces, we used atomic force microscopy in an intermittent contact mode coupled with a modulated voltage to realized local anodization at a nanometer scale. This method leads, after a few tens of milliseconds of oxidation, to an oxide height saturation and a low lateral growth rate for both surfaces. These specific results were used to control separately both the depth and the diameter of holes and to obtain compatible pattern for QD growth. We also demonstrated the thermal stability of these patterns at compatible temperatures with the InAs QD growth. First, results of QD growth on these patterns are presented.

In this paper, we report morphology of silicon nanowires (Si-NWs) grown on various surfaces and patterned substrates using Vapor–Liquid–Solid (VLS) and Solid–Liquid–Solid (SLS) techniques. It is observed that the growth conditions are critical in controlling the dimensions of wires in both techniques. In addition to this, it is also demonstrated that Si-NWs are essentially different grown on Si or GaAs substrates. For growth of Si-NWs by VLS, Si powder was evaporated in a tube furnace under Ar flow while substrates were kept at different temperatures. In SLS, experimental conditions were identical except that no external source was used. Si-NWs thus grown showed dependence on the flow rate of Ar gas and the temperature of the substrate. Interestingly, instead of only radial nannowires (NWs), nanobelts and tapered NWs were also grown on patterned Au-catalyzed GaAs surface. In the end, the analysis on the basis of existing theories of NW growth is presented. Optical properties of Si-NWs are also briefly discussed.

It is well known that a circular hole in a blanket thin film causes strain concentration near the hole edge when the thin film is under tension. The increased strain level can be as high as three times of the applied tension. Interestingly, we show that, by suitably patterning an array of circular holes in a thin film, the resulting strain in the patterned film can be decreased to only a fraction of the applied tension, even at the hole edges. The strain deconcentration in the film originates from the following deformation mechanism: while initially planar, the film patterned with circular holes elongates by deflecting out of plane, so that a large tension induces only small strains. Using finite element simulations, we investigate the effects of geometric parameters (i.e., hole size, spacing, and pattern) and loading direction on the resulting strain in patterned thin films under tension. The large deformability of the patterned film is independent of materials and length scale, and thus sheds light on a potential architecture concept for flexible electronics.

We present the effect of post-implantation annealing conditions on the structural and optical quality of InAs quantum dots (QDs) grown by combination of focused ion beam (FIB) and molecular beam epitaxy (MBE) approach. A FIB of Ga⁺ ion was employed to pattern a homogeneously GaAs buffer layers and then, an in situ annealing step followed by InAs deposition was performed. Three different post-implantation annealing conditions were tested and under well-optimized conditions, a dislocation and defect-free InAs QDs growth on FIB patterned surface was successfully achieved. Furthermore, using photoluminescence (PL) study, we demonstrate that our best sample shows almost similar optical quality as MBE grown QDs on unimplanted GaAs surface. The patterning technique described here can presumably be applied to systems other than InAs/GaAs and highly interesting for site-controlled nucleation of QDs that finds its potential applications in nanooptoelectronic devices.

Micron-scale ordered gold patterns were deposited through a metallic copper grid positioned onto graphene oxide (GO) film. The exposure to a xenon light source results in the formation of conductive GO/metal interface with photocurrent generation. It is suggested that such simple method might serve as an efficient path for the formation of multifunctional patterned metal-carbon interconnects.

Hydroxyapatite (HA)-coated metallic prostheses, which combine the osteoconductivity of HA and high strength of metallic alloys, have been increasingly the choice of joint replacement prostheses by surgeons as the general population lives longer. Surface modification of metallic implant surfaces is one of the key focal points to implantation technology. In addition to material chemistry, surface topography has been found to positively impact cellular response and is able to enhance the life time of the implant. Recently, a new technique, template-assisted electrohydrodynamic atomization (TAEA) spraying, developed using the principles of electrohydrodynamic atomization spraying, which is an electrically driven jet-based deposition method, is of considerable interest in surface topography formation. The process offers the attractive advantages of compatibility with micro-fabrication technology and versatility in pattern specification for advanced implant designs. This technology incorporates nanosized calcium phosphate to mimic the size and chemical composition of bone mineral in a micrometer-dimension pattern configuration to guide cellular responses. In vitro studies showed that both pillar and track nano Silicon-substituted HA (SiHA) patterns were able to encourage the attachment and growth of osteoblast cells, the track patterns provided the favourite surface for the initial cell attachment while a fast cell proliferation rate was found on the pillar pattern from day 1 to day 5 in comparison with that of a SiHA-coated surface. The alignment of actin cytoskeleton of osteoblast cells matched the orientation of the entire cell. The shear peel strength of the patterned interlocking nano-HA coating was found to be at least an order of magnitude higher than the conventional HA coating. Therefore, TAEA offers great potential for producing new coatings with a tailored surface topography, on both the micro- and nano-scale in a more cost effective way to enhance the performance of medical implants.

By means of frequencies derived from the mathematics of the Mereon Matrix, the CymaScope (a sonic visualising technology presented in Appendix B) was used to make the matrix visible in the predicted medium, water (see the Preface to the First Edition). It revealed minute details of the complex structure and the dynamics of Mereon Matrix. This chapter summarises a series of related investigations made using the CymaScope. This technology revealed how the difference of only 1/100th of a hertz makes a remarkable distinction; cymatic images of living matter are shown to display the Mereon symmetry, expanding our understanding and increasing our ability to consider how this vibratory pattern relates to how everything is connected.

The germ layer of the endoderm can contribute to the formation of both the gastrointestinal and respiratory tracts, and other associated organs. The endoderm is generally responsible for the formation of the internal epithelial tube that will eventually become the digestive tract. During embryogenesis, the endoderm represents the inner germ layer in both triploblastic and diploblastic embryos. The anterior–posterior (A–P) and proximal–distal (P–D) patterning are among the earliest developmental events during embryogenesis. They are tightly regulated with a highly coordinated network of several signaling molecules and pathways. Accumulated data in the last two decades from studies on animal model organisms have enhanced our understanding of the anterior endoderm development and patterning and P–D patterning of the lung. These data have also uncovered many of the molecular mechanisms and signaling molecules that regulate these processes. In this chapter, we will describe this progress with a focus on the anterior endodermal patterning and its regulatory molecular mechanisms and signaling pathways, as well as the P–D patterning of lung embryonic cells. Lastly, we discuss the role of stem and progenitor cells in the P–D patterning of the lung.