System Characterization, Modelling, Designing and Integrative Analysis of Nanosystems

Abstract

Much of the fascination with nanotechnology stems from these quantum and surface phenomena that matter exhibits at the nanoscale. Two main approaches are used in nanotechnology. In the "bottom-up" approach, materials and devices are built from molecular components which assemble themselves chemically by principles of molecular recognition. In the "top-down" approach, nano-objects are constructed from larger entities without atomiclevel control. Nanotechnology is considered a key technology for the future. Nanotechnology entails the application of fields of science as diverse as surface science, organic chemistry, molecular biology, semiconductor physics, micro-fabrication, etc. Nanotechnology distinct from devices which are merely miniaturized versions of an equivalent macroscopic device; such devices are on a larger scale and come under the description of micro technology In this thesis work, an attempt is made to develop an integrated systems model for the structure of the nanotechnology system in terms of its constituents and interactions between the constituents and processes etc, using graph theory and matrix algebra. The nanotechnology system is first modelled with the help of graph theory, then by a variable adjacency matrix and then by a multinomial known as a permanent function. The permanent function provides an opportunity to carry out structural analysis of the nanotechnology system in terms of strength, weakness, improvement and optimization by correlating the different system with its structure. A physical meaning has been associated with each term of the permanent function. Different structural attributes of the nanotechnology system are identified to develop a graph theoretic model, a matrix model and a multinomial permanent model of the nanotechnology system. A top-down approach for complete analysis of any nanotechnology system is also given. A general methodology is also presented for characterization and comparison of two nanotechnology systems. Usefulness of the present methodology is also illustrated. While modelling a nanotechnology system, nanomaterial selection is one of the mostly encountered decision problems in material science literature, is still an onerous task for manufacturing organisations. Problem has become more difficult in recent years due to increasing complexity, available features, and facilities offered by different nanomaterial products. Here generation and maintenance of reliable and exhaustive data of nanomaterial based on their different pertinent attributes is done. It is useful for better understanding, comparison and analysis and for comparison; ranking and optimum selection of nanomaterial from a large number of nanomaterial available in global market, the multiple attribute decision making problems is solved by “TOPSIS” (Technique for Order Preferences by Similarity to Ideal Solution). The techniques convert database into knowledge base by considering normalization, relative weights, positive benchmarked and negative benchmarked solutions and normalized weighted database into single numerical suitability index for each candidate nanomaterial solution. It helps the nanomaterial user to save time by providing a tool for selecting the nanomaterial most suited for his operational needs. The selection procedure allows rapid convergence from large number of candidate nanomaterial to a manageable shortlist of potentially suitable nanomaterial using elimination search based on the few critical selection attributes. Subsequently, the selection procedure proceeds to rank the alternatives in the shortlist by employing different attributes based specification and graphical methods. The ranks of the candidate nanomaterial are calculated with respect to the best possible nanomaterial, say +ve benchmark nanomaterial, for particular application. The coding scheme and the selection procedures, mathematical and graphical, are illustrated with example. After selecting appropriate nanomaterial as per the requirements for designing nanodevices organizations are deploying well designed nanoactuators supporting converged applications of defence, mechanical industry and biological applications etc. Use of different applications demands nanoactuator to have various abilities – actuation, modification, ii realization, performance etc, called x- abilities- in varying degree of importance depending on application requirements of an organization. To facilitate design of nanoactuator simultaneously for all x – abilities in an integrated way, a concurrent design methodology using multiple attribute decision making (MADM) approach is proposed. This concurrent design methodology is aimed at including design time considerably and makes use of expertises of experts from different specialized fields in a single design team. MADM approach provides technique for selection of best nanoactuator for the application under consideration. In this way, with proper system characterization, analysis and designing of the nanosystems may lead to a better production of the nanodevices as per the required applications.