This thesis will address the controlled growth of carbon nanotubes (CNTs) using two different methods i.e. (1) Microwave Enhanced Plasma Chemical Vapour Deposition (ME-PECVD) and (2) Thermal CVD. The micro-structural and compositional analysis of the samples were investigated by various techniques such as the Scanning Electron Microscopy (SEM), Raman spectroscopy, High Resolution Transmission Electron Microscopy (HRTEM), X-ray Diffraction (XRD), and static contact angle studies. Electric field emission properties were also studied. Fabrication of microfluidic channels and the integration of CNTs in microfluidic channels is also investigated. In this work, the effect of catalyst thickness and growth-time of carbon nanotubes (CNTs) by microwave plasma chemical vapour deposition (MPCVD) technique was investigated. Also the role of a thin buffer layer (Aluminium in this case) under the catalyst was also explored. CNTs were grown by a thermal chemical vapour deposition (TCVD) method and the effect of CNT growth on various substrates, using TCVD process, was studied. CNTs were also grown in various patterns via the two different techniques as mentioned above. The effect of pattern-size on the growth of vertically aligned CNT pillars was investigated. The catalyst patterns were made using two commonly used techniques (i) maskless photolithography (ii) nano/micro sphere lithography. The effect of patterns on CNTs field emission and micro-structural properties was also studied. These patterns were made on silicon as well as on quartz and also integrated in microfluidic channels for micro-particle filtration application. Due to their hydrophobic nature, CNTs are the least preferred material as far as contact with liquid is concerned. In this work, CNTs were functionalised using two different methods, with a view of keeping their vertical alignment intact and reducing the contact angle. The vertically aligned MWCNTs synthesised by MPECVD and TCVD were treated in a low power oxygen plasma, which resulted in (i) lower contact angle with vertical alignment intact (ii) the efficient removal of metal caps at the nanotube tips and (iii) incorporation of oxygen into the CNTs making them better field emitter. These experiments on the CNTs revealed O2 plasma functionalization, as a novel, non toxic, technique that can be used for the purifying, functionalization and tip opening of the CNTs. The XPS and Raman validated the plasma cleaning and defect generation in the CNTs, while, XPS, SEM and Raman showed the efficient removal of metal catalyst from the nanotube tips in the vertically aligned MWCNTs. Another area explored in this research work was the fabrication of microfluidic channels. A commonly used photolithographic technique was used for the micro channel fabrication using SU8 as a photoresist on silicon/glass/quartz. Also a hot-embossing technique was used to fabricate polymeric micro-channels. The integration of CNTs in microfluidic channels, in order to use them as micro-particle filters, was also studied. Due to the lower glass transition temperature of polymers a novel technique was needed to transfer vertically aligned CNTs onto the polymers for microfluidic based filters. In this work a hot-embossing technique was used to transfer the VACNTs onto the microfluidic channels. It was found that this process gives complete transfer of CNTs from the substrate to the polymeric channels. Finally, a CNT based microfluidic device was fabricated using lithographic and hot embossing techniques. Optimised device fabrication conditions and the role of CNTs as a micro particle filter is investigated.

The way the temperature is distributed inside the material is of prime importance in laser materials processing. Optimisation of different laser processes requires control over the temperature distribution in order to control microstructure and residual stressesb y manipulating heating/cooling rates and thermal gradients. Currently most of the laser material processing is carried out by either circular or rectangular beam geometry with variation in temperature distribution caused by either the variation of laser power, spot size or scanning speed. Variations in these parameters are often limited by other processing conditions, therefore the possibility of modifying the microstructure and residual stresses are limited. If any other parameter can be identified, such that variation of this parameter alone (i. e. without changing the laser power or scanning speed) can alter the temperature distribution, then it will provide added flexibility to the process control. One possible method of varying the temperature distribution, and hence the heating /cooling rates and thermal gradients is to modify the geometry of laser beams. The effect of laser beam geometry, particularly of non-conventional laser beam geometries on laser processing of materials has received very little attention. This thesis presents a detailed numerical investigation of the effects of non-conventional laser beam geometries on laser surface heating, laser transformation hardening, laser tube bending and laser melting of metallic materials. The numerical models have been validated by experiments using a diode laser. The temperature distributions, heating/cooling rates, thermal gradients, stress distributions and distortions were evaluated. The work presented in this thesis highlights the different attributes of conventional and non-conventional laser beam geometries. Laser beam geometries were found to influence heating and cooling rates as well as residual and normal stress distributions in materials processing. In particular, the donut beam results in transient bi-axial stress state which does not exist for any other solid beam geometry. These attributes can be utilised as an advantage not only in the investigated processes but could also be utilised for improving various other laser material processes

The research presented in this thesis focuses on the development of tactile event signature sensors and their application, especially in reactive behaviour-based robotic assembly systems. In pursuit of practical and economic sensors for detecting part contact, the application of PVDF (polyvinylidene fluoride) film, a mechanical vibration sensitive piezo material, is investigated. A <I>Clunk Sensor</I> is developed which remotely detects impact vibrations, and a <I>Push Sensor</I> is developed which senses small changes in the deformation of a compliant finger surface. The <I>Push Sensor</I> is further developed to provide some force direction and force pattern sensing capability. By being able to detect changes of state in an assembly, such as a change of contact force, an assembly robot can be well informed of current conditions. The complex structure of assembly tasks provides a rich context within which to interpret changes of state, so simple binary sensors can conveniently supply a lot more information than in the domain of mobile robots. Guarded motions, for example, which require sensing a change of state, have long been recognised as very useful in part mating tasks. Guarded motions are particularly well suited to be components of assembly behavioural modules. In behaviour-based robotic assembly systems, the high level planner is endowed with as little complexity as possible while the low level planning execution agent deals with actual sensing and action. Highly reactive execution agents can provide advantages by encapsulating low level sensing and action, hiding the details of sensori-motor complexity from the higher levels. Because behaviour-based assembly systems emphasise the utility of this kind of qualitative state-change sensor (as opposed to sensors which measure physical quantities), the robustness and utility of the <I>Push Sensor</I> was tested in an experimental behaviour-based system. An experimental task of pushing a ring along a convoluted stiff wire is chosen, in which the tactile sensors developed here are aided by vision. Three different methods of combining these different sensors within the general behaviour-based paradigm are implemented and compared. This exercise confirms the robustness and utility of the PVDF-based tactile sensors. We argue that the comparison suggests that for behaviour-based assembly systems using multiple concurrent sensor systems, bottom-level motor control in terms of force or velocity would be more appropriate than positional control. Behaviour-based systems have traditionally tried to avoid symbolic knowledge. Considering this in the light of the above work, it was found useful to develop a taxonomy of type of knowledge and refine the prohibition.

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