Alignment of liquid crystal/carbon nanotube dispersions for application in unconventional computing

We demonstrate the manipulation of single-walled carbon nanotube/liquid crystal composites using in-plane electric fields. The conductivity of the materials is shown to be dependant on the application of a DC bias across the electrodes. When the materials are subjected to this in-plane field, it is suggested that the liquid crystals orientate, thereby forcing the SWCNTs to follow in alignment. This process occurs over many seconds, since the SWCNTs are significantly larger in size than the liquid crystals. The opportunity for applying this material to unconventional computing problems is suggested

A investigação enquanto prática de deliberação curricular: o caso do projecto ICR

Este artigo refere-se a um projecto de investigação curricular colaborativa que nasceu da conjugação entre, por um lado, a preocupação de alguns professores do ensino básico com o desinteresse manifestado por determinados alunos em relação à escola e ao currículo e, por outro, o interesse de alguns professores universitários em estudar questões de relevância curricular. Dessa conjugação resultou a assunção de uma dimensão investigativa na prática profissional dos referidos professores do ensino básico, concretizada num projecto de investigação-acção colaborativa conduzido por uma equipa de quatro docentes universitários e dez docentes do ensino básico (todos os ciclos), que têm estudado a problemática do reconhecimento (ou não), por parte dos alunos, da relevância das aprendizagens escolares. A recolha de dados tem sido feita em sucessivos ciclos de investigação-acção, com a duração de um ano escolar cada, principalmente através do registo sistemático de manifestações de desinteresse (por parte dos alunos em relação ao currículo) observadas nas aulas e de entrevistas aos alunos, conduzidas pelos seus professores. Os dados têm sido analisados pelos próprios professores do ensino básico, com o apoio dos docentes universitários, e sujeitos a interpretações individuais e de equipa, sendo essas interpretações inspiradoras de novas estratégias de ensino, que são continuamente monitorizadas e revistas. Os processos já amadurecidos e os resultados já gerados sugerem que, apesar da existência de algumas dificuldades, é possível desenvolver nas escolas do ensino básico práticas de gestão curricular que integrem uma componente de investigação.ABSTRACT: This article describes a project of collaborative research on curriculum, which was created by a team that includes (1) elementary school teachers worried about the lack of interest shown by some of their students with regard to the school and the curriculum, and (2) university professors interested in studying issues of curriculum relevance. This partnership has contributed to an increased use of research in classrooms by those elementary school teachers, through an action research project focused on students’ acknowledgment of the relevance of what they learn in school. Data has been collected in successive cycles of action research, mainly through classroom field notes that provide evidence of given students’ lack of interest with regard to the curriculum, and through interviews conducted by the teachers. Each action research cycle is one school year long. Data have been analyzed by the elementary school teachers, sometimes with support from the university professors, and interpreted both individually and collectively. Such interpretation of data inspires teachers in designing new teaching strategies, which are continuously monitored and reviewed. The processes that have already been consolidated and the results that have already been generated by this project suggest that, despite some difficulties, it is possible to develop curricula in elementary schools in ways that entail research

Computing with carbon nanotubes: optimization of threshold logic gates using disordered nanotube/polymer composites

This paper explores the use of single-walled carbon nanotube (SWCNT)/poly(butyl methacrylate) composites as a material for use in unconventional computing. The mechanical and electrical properties of the materials are investigated. The resulting data reveal a correlation between the SWCNT concentration/viscosity/conductivity and the computational capability of the composite. The viscosity increases significantly with the addition of SWCNTs to the polymer, mechanically reinforcing the host material and changing the electrical properties of the composite. The electrical conduction is found to depend strongly on the nanotube concentration; Poole-Frenkel conduction appears to dominate the conductivity at very low concentrations (0.11% by weight). The viscosity and conductivity both show a threshold point around 1% SWCNT concentration; this value is shown to be related to the computational performance of the material. A simple optimization of threshold logic gates shows that satisfactory computation is only achieved above a SWCNT concentration of 1%. In addition, there is some evidence that further above this threshold the computational efficiency begins to decrease

Training a Carbon-Nanotube/Liquid Crystal Data Classifier Using Evolutionary Algorithms

Evolution-in-Materio uses evolutionary algorithms (EA) to exploit the physical properties of unconfigured, physically rich materials, in effect transforming them into information processors. The potential of this technique for machine learning problems is explored here. Results are obtained from a mixture of single walled carbon nanotubes and liquid crystals (SWCNT/LC). The complex nature of the voltage/current relationship of this material presents a potential for adaptation. Here, it is used as a computational medium evolved by two derivative-free, population-based stochastic search algorithms, particle swarm optimisation (PSO) and differential evolution (DE). The computational problem considered is data classification. A custom made electronic motherboard for interacting with the material has been developed, which allows the application of control signals on the material body. Starting with a simple binary classification problem of separable data, the material is trained with an error minimisation objective for both algorithms. Subsequently, the solution, defined as the combination of the material itself and optimal inputs, is verified and results are reported. The evolution process based on EAs has the capacity to evolve the material to a state where data classification can be performed. PSO outperforms DE in terms of results’ reproducibility due to the smoother, as opposed to more noisy, inputs applied on the material

Evolution of Electronic Circuits using Carbon Nanotube Composites

Evolution-in-materio concerns the computer controlled manipulation of material systems using external stimuli to train or evolve the material to perform a useful function. In this paper we demonstrate the evolution of a disordered composite material, using voltages as the external stimuli, into a form where a simple computational problem can be solved. The material consists of single-walled carbon nanotubes suspended in liquid crystal; the nanotubes act as a conductive network, with the liquid crystal providing a host medium to allow the conductive network to reorganise when voltages are applied. We show that the application of electric fields under computer control results in a significant change in the material morphology, favouring the solution to a classification task