Chemical Bionics - a novel design approach using ion sensitive field effect transistors

In the late 1980s Carver Mead introduced Neuromorphic engineering in which various aspects of the neural systems of the body were modelled using VLSI1 circuits. As a result most bio-inspired systems to date concentrate on modelling the electrical behaviour of neural systems such as the eyes, ears and brain. The reality is however that biological systems rely on chemical as well as electrical principles in order to function. This thesis introduces chemical bionics in which the chemically-dependent physiology of specific cells in the body is implemented for the development of novel bio-inspired therapeutic devices. The glucose dependent pancreatic beta cell is shown to be one such cell, that is designed and fabricated to form the first silicon metabolic cell. By replicating the bursting behaviour of biological beta cells, which respond to changes in blood glucose, a bio-inspired prosthetic for glucose homeostasis of Type I diabetes is demonstrated. To compliment this, research to further develop the Ion Sensitive Field Effect Transistor (ISFET) on unmodified CMOS is also presented for use as a monolithic sensor for chemical bionic systems. Problems arising by using the native passivation of CMOS as a sensing surface are described and methods of compensation are presented. A model for the operation of the device in weak inversion is also proposed for exploitation of its physical primitives to make novel monolithic solutions. Functional implementations in various technologies is also detailed to allow future implementations chemical bionic circuits. Finally the ISFET integrate and fire neuron, which is the first of its kind, is presented to be used as a chemical based building block for many existing neuromorphic circuits. As an example of this a chemical imager is described for spatio-temporal monitoring of chemical species and an acid base discriminator for monitoring changes in concentration around a fixed threshold is also proposed

The contribution of hydrogen to the corrosion of 2024 aluminium alloy exposed to thermal and environmental cycling in chloride media

This work is focused on the role of hydrogen in corrosion damage induced by the cyclic exposure of 2024 aluminium alloy to chloride media with air emersion periods at room and/or negative temperatures. Various analysis and microscopic observation techniques were applied at intergranular corrosion defects. A mechanism involving the contribution of hydrogen to the degradation of the alloy mechanical properties is presented. Several consecutive stress states appear during cycling, resulting from volume expansion of the electrolyte trapped in the intergranular defects during emersion phases at -20°C. These stress states lead to hydrogen diffusion, transport and trapping

Editorial: Innovation in aviation and space for opening new horizons

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Mechanical and nanomechanical properties of MWCNT/PP nanocomposite

The mechanical and nanomechanical properties of multi-walled carbon nanotube-reinforced polypropylene (MWCNT/PP) nanocomposite were investigated through tension tests (conducted on 2 wt% and 5 wt% specimens) and nanoindentation tests (conducted on 2 wt% specimens). In addition, the structural properties and topography of the nanocomposite were characterized by means of scanning electron microscopy (SEM) and Scanning Probe Microscopy (SPM), respectively. The results from the tension tests reveal an enhancement and a considerable scatter in the Youngs modulus and maximum stress of the MWCNT/PP nanocomposite for both MWCNT content. For the specimens with mechanical properties lower than the average values, the SEM and SPM images revealed poor dispersion and formation of large agglomerates. The hardness (as resistance to applied load) and Young蒒s modulus were mapped at 300 nm of displacement, for a grid of 70 ( 70 �m2. Through projection, the resistance is clearly divided into 3 regions, namely the PP matrix, the interphase (region close to/between MWCNTs) and the regions of the MWCNT agglomerates. The resistance deviates from low values (few MPa) to 1.8 GPa. The present experimental study provides all necessary data for the model creation and validation of the MWCNT/PP nanocomposite

Mechanical and nanomechanical properties of MWCNT/PP nanocomposite

The mechanical and nanomechanical properties of multi-walled carbon nanotube-reinforced polypropylene (MWCNT/PP) nanocomposite were investigated through tension tests (conducted on 2 wt% and 5 wt% specimens) and nanoindentation tests (conducted on 2 wt% specimens). In addition, the structural properties and topography of the nanocomposite were characterized by means of scanning electron microscopy (SEM) and Scanning Probe Microscopy (SPM), respectively. The results from the tension tests reveal an enhancement and a considerable scatter in the Young’s modulus and maximum stress of the MWCNT/PP nanocomposite for both MWCNT content. For the specimens with mechanical properties lower than the average values, the SEM and SPM images revealed poor dispersion and formation of large agglomerates. The hardness (as resistance to applied load) and Young’s modulus were mapped at 300 nm of displacement, for a grid of 70 ´ 70 μm2. Through projection, the resistance is clearly divided into 3 regions, namely the PP matrix, the interphase (region close to/between MWCNTs) and the regions of the MWCNT agglomerates. The resistance deviates from low values (few MPas) to 1.8 GPa. The present experimental study provides all necessary data for the model creation and validation of the MWCNT/PP nanocomposite

Effect of corrosion and sandblasting on the high cycle fatigue behavior of reinforcing B500C steel bars

In a series of applications, steel reinforced concrete structures are subjected to fatigue loads during their service life, what in most cases happens in corrosive environments. Surface treatments have been proved to represent proper processes in order to improve both fatigue and corrosion resistances. In this work, the effect of corrosion and sandblasting on the high cycle fatigue behavior reinforcing steel bars is investigated. The investigated material is the reinforcing steel bar of technical class B500C, of nominal diameter of 12 mm. Steel bars specimens were first exposed to corrosion in alternate salt spray environment for 30 and 60 days and subjected to both tensile and fatigue tests. Then, a series of specimens were subjected to common sandblasting, corroded and mechanically tested. Metallographic investigation and corrosion damage evaluation regarding mass loss and martensitic area reduction were performed. Tensile tests were conducted after each corrosion exposure period prior to the fatigue tests. Fatigue tests were performed at a stress ratio, R, of 0.1 and loading frequency of 20 Hz. All fatigue tests series as well as tensile test were also performed for as received steel bars to obtain the reference behavior. The results have shown that sandblasting hardly affects the tensile behavior of the uncorroded material. The effect of sandblasting on the tensile behavior of pre-corroded specimens seems to be also limited. On the other hand, fatigue results indicate an improved fatigue behavior for the sandblasted material after 60 days of corrosion exposure. Martensitic area reductions, mass loss and depth of the pits were significantly smaller for the case of sandblasted materials, which confirms an increased corrosion resistance

Manufacture of a rotor blade pitch horn using binder yarn fabrics

The use of binder yarn fabrics in rotor blade applications is investigated in this work. A preforming procedure is incorporated in manufacturing, resulting in higher degree of automation and a reduction of process steps. The performance of the process is evaluated with respect to cost savings compared to prepregging technologies