ToPoliNano: Nanoarchitectures Design Made Real

Many facts about emerging nanotechnologies are yet to be assessed. There are still major concerns, for instance, about maximum achievable device density, or about which architecture is best fit for a specific application. Growing complexity requires taking into account many aspects of technology, application and architecture at the same time. Researchers face problems that are not new per se, but are now subject to very different constraints, that need to be captured by design tools. Among the emerging nanotechnologies, two-dimensional nanowire based arrays represent promising nanostructures, especially for massively parallel computing architectures. Few attempts have been done, aimed at giving the possibility to explore architectural solutions, deriving information from extensive and reliable nanoarray characterization. Moreover, in the nanotechnology arena there is still not a clear winner, so it is important to be able to target different technologies, not to miss the next big thing. We present a tool, ToPoliNano, that enables such a multi-technological characterization in terms of logic behavior, power and timing performance, area and layout constraints, on the basis of specific technological and topological descriptions. This tool can aid the design process, beside providing a comprehensive simulation framework for DC and timing simulations, and detailed power analysis. Design and simulation results will be shown for nanoarray-based circuits. ToPoliNano is the first real design tool that tackles the top down design of a circuit based on emerging technologie

Enabling Design and Simulation of Massive Parallel Nanoarchitectures

A common element in emerging nanotechnologies is the increasing complex- ity of the problems to face when attempting the design phase, because issues related to technology, specific application and architecture must be evalu- ated simultaneously. In several cases faced problems are known, but require a fresh re-think on the basis of different constraints not enforced by standard design tools. Among the emerging nanotechnologies, the two-dimensional structures based on nanowire arrays is promising in particular for massively parallel architec- tures. Several studies have been proposed on the exploration of the space of architectural solutions, but only a few derived high-level information from the results of an extended and reliable characterization of low-level structures. The tool we present is of aid in the design of circuits based on nanotech- nologies, here discussed in the specific case of nanowire arrays, as best candi- date for massively parallel architectures. It enables the designer to start from a standard High-level Description Languages (HDL), inherits constraints at physical level and applies them when organizing the physical implementation of the circuit elements and of their connections. It provides a complete simu- lation environment with two levels of refinement. One for DC analysis using a fast engine based on a simple switch level model. The other for obtaining transient performance based on automatic extraction of circuit parasitics, on detailed device (nanowire-FET) information derived by experiments or by existing accurate models, and on spice-level modeling of the nanoarray. Re- sults about the method used for the design and simulation of circuits based on nanowire-FET and nanoarray will be presente

Suspension Near-Field Electrospinning: a Nanofabrication Method of Polymer Nanoarray Architectures for Tissue Engineering

Chapter 1. This chapter is divided into six sections. The first will discuss the issue of nerve tissue loss, and the strategies of therapy (1.1). The second describes the role of nanofabrication in tissue engineering (1.2). The third section details the theoretical background of electrospinning in terms of solution and process parameters (1.3). The fourth section introduces near-field electrospinning (NFES), recent advances in this field and the principles of NFES techniques (1.4). The fifth section details objectives for a tissue engineered construct for neural cell therapy, and presents possible viable solutions (1.5). The sixth summarizes the aims and structure of this thesis (1.6)..

Atomic Layer Deposition Seeded ZnO Nanowires in Hybrid Carbon Fiber Composites: Synthesis, Characterization and Multifunctionality

Interfacial treatments of carbon fiber composites play a critical role in determining the overall performance as the surface of carbon fiber is smooth and inert causing low bonding to the polymer matrix. In this dissertation, atomic layer deposition (ALD) seeded ZnO nanowires were grown on carbon fiber as an enhanced interphase using two-step hydrothermal method for the first time. The effects of growth parameters of seed layers by ALD and nanowire growth in hydrothermal method were systematically investigated. Several morphologies of ZnO nanostructures were obtained and characterized using field emission scanning electron microscope (FESEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Single carbon fiber composites and carbon fiber composite laminates with ZnO nanowires were manufactured, then tested by single fiber fragmentation test, 3-point bending test, short beam 3-point bending test. It was found that the incorporation of ZnO nanowires significantly improved the mechanical properties of composites including interfacial shear strength, flexural strength and interlaminar shear strength by up to 286%,45.6% and 31.1%.The successful development and characterization of ZnO nanowires enhanced structural composites have great potential to lead to new generation of lightweight materials with increased mechanical properties for broad mechanical and aerospace engineering applications

Detection of failures in antenna arrays through a Lebesgue-space approach

In this paper, a novel antenna array diagnostic approach is presented. The failures in antenna arrays are detected by means of a non-Hilbertian Lebesgue-space L-p technique to solve the underlying inverse problem. The solution of this inverse problem enables to retrieve the distribution of faulty feed excitations of the antenna under test starting from far-field measurements. The developed approach has been numerically validated. Simulations concern planar arrays where different rates and distributions of failures have been tested. Results show good capabilities in detecting damaged regions in the analyzed scenarios

Interleaving in Systolic-Arrays: a Throughput Breakthrough

In past years the most common way to improve computers performance was to increase the clock frequency. In recent years this approach suffered the limits of technology scaling, therefore computers architectures are shifting toward the direction of parallel computing to further improve circuits performance. Not only GPU based architectures are spreading in consideration, but also Systolic Arrays are particularly suited for certain classes of algorithms. An important point in favor of Systolic Arrays is that, due to the regularity of their circuit layout, they are appealing when applied to many emerging and very promising technologies, like Quantum-dot Cellular Automata and nanoarrays based on Silicon NanoWire or on Carbon nanotube Field Effect Transistors. In this work we present a systematic method to improve Systolic Arrays performance exploiting Pipelining and Input Data Interleaving. We tackle the problem from a theoretical point of view first, and then we apply it to both CMOS technology and emerging technologies. On CMOS we demonstrate that it is possible to vastly improve the overall throughput of the circuit. By applying this technique to emerging technologies we show that it is possible to overcome some of their limitations greatly improving the throughput, making a considerable step forward toward the post-CMOS era

Biomimetic substrates for immune cell activation

This thesis describes the fabrication of biomimetic substrates, and their use as tools to probe cellular interactions of key immune cells. Nanoparticles of gold and zinc sulfide have been fabricated, and patterned into nanoarrays. Adaptive (T cell) and innate (NK cell) immune cell responses to nanoscale spacing of ligand-receptor pairs were measured, and the effect of presenting stimulatory ligands on substrates with varying mechanical properties has been tested for T cell responses. The advanced materials in this thesis act to create artificial immune synapses, and probe the effect of these stimuli on engagement and activation of human immune cells. Specifically, block co-polymers were used to form polymer micelles which encapsulate metal ions and form metal or metal compound nanoparticles. Micelles encapsulating metal ions or nanoparticles were formed and deposited onto substrates using Block Co-polymer Micellar Lithography (BCML) to form nanoparticle arrays with controlled inter-particle spacing. Well controlled gold nanoparticle arrays with spacing between 25-150nm have been produced. The technique has been further developed to include fabrication of zinc sulfide particles and nanoarrays. Zinc sulfide nanoparticles showed a unique internal structure with 5nm crystalline domains set in an amorphous matrix and an optical band gap of between 3.88-4.28eV. Nanoparticle arrays were then functionalised with biological ligands, notably antibodies that engage with the NK cell surface receptor CD16, or the T cell TCR/CD3 moiety. The cellular response to these materials was measured, and was sensitive to the nanoscale arrangement of stimulatory ligands; both cell types responded to ligands with 25nm, but not 104nm, inter-ligand spacing. In an alternative approach, spherical PEG hydrogel particles of diameter 5-50μm were formed with controlled rigidity between 3-2000kPa. T cell response as a function of substrate rigidity was tested, and cells showed maximal response to anti-CD3 functionalised substrates with rigidities of 3-5kPa.Open Acces

Interfaces and Device Geometry of PbS Colloidal Quantum Dots (CQDs) Solar Cells

The unique properties of lead sulfide (PbS) colloidal quantum dot solar have attracted great interest cells as an emerging photovoltaic technology. In this thesis, a comprehensive study on improving the device performance is carried out through several architectural and materials approaches: 1) introducing a periodic submicron grating pattern, 2) optimizing the film morphology of its electron transport interface, and 3) investigating the physical deposition of the PbS quantum dots. We demonstrated, from both simulation and the experimental results, that by employing a grating pattern, the light absorption-charge carrier compromise could be relaxed since more light absorbing material is packed without upsetting the transport length limit. This results in an increase both in JSC and power conversion efficiency of the device. The same geometry has an added mechanical bonus, allowing a super-flexibility without cracking brittle thin films. A highly flexible and transparent ITO pattern was developed on PET films which survived in our cycling bending test with a minimum diameter of curvature of 3.2 mm and maintained more than 90% of optical transparency over the whole visible wavelength. Subsequently, this patterned ITO/PET substrate demonstrated a promising application for flexible solar cells in our CQDs study. Regarding the electron interface, we explored the effects of various film growth conditions of ZnO between the ITO and the CQDs layer. Our study showed that the device performance could be significantly improved by a ZnO film with optimized morphology realized under specific oxygen pressure during pulsed laser deposition (PLD), in which the carrier transport is facilitated due to limited bimolecular recombination. Finally, by employing PLD, the photo-oxidation rate as function of light intensity, temperature and oxygen pressure of PbS QDs fabricated by this technique is quantitatively studied. The combined effect of these factors results in a reduced energy barrier that allows the oxidation to proceed at a high rate. These results highlight the importance of photo-excitation on the speed of the oxidation process even at low illumination conditions. Out of this finding a quantitative standard is set up which is useful for characterizing the stability of quantum dots coated with ligands/linkers, and to compare different protection schemes in a fair quantitative way, providing us some guidance on the PbS surface passivation strategy to achieve better PbS CQDs solar cell performance.Doctor of Philosoph