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.

Langmuir-Blodgett films: a new class of pyroelectric materials.

The authors report on a novel method for producing the noncentrosymmetric structures necessary for the observation of the pyroelectric effect. The Langmuir-Blodgett technique has been used to fabricate ultrathin films consisting of alternate layers of 22-tricosenoic acid and 1-docosylamine. The pyroelectric coefficient has been determined using both static and dynamic detection techniques, is approximately 0.2 nC cm(-2) K(-1) (static value); this value is independent of the film thickness in the range of 11 to 99 monolayers, but increases slightly if a substrate of lower thermal expansion coefficient is used. The results indicate that there is a piezoelectrically induced secondary effect contributing to the overall pyroelectric activity.

Application of multilayer films to molecular sensors: some examples of bioengineering at the molecular level.

The Langmuir-Blodgett technique is now a well established method for producing ultra-thin organic films on solid surfaces. These layers could find wide ranging uses in electronic and optoelectronic devices, or even as the basis of artificial biological systems. In this paper the film deposition process is briefly reviewed. Examples of multilayers incorporating biological molecules are presented and possible applications for such films in sensing structures are briefly discussed.

Observation of electro-optic and electroabsorption modulation in a Langmuir-Blodgett film Fabry-Perotétalon.

Electro-optic and electroabsorption modulation by use of a Langmuir-Blodgett (LB) film-based Fabry-Perot étalon is reported. The modulation was found to be dominated by linear effects in the film. The percentage change in transmission was 15% for electro-optic and 30% for electroabsorption modulation at an rms drive voltage of 53 V. The effective linear electro-optic coefficient of the LB film was 13 pm V(-1) at 633 nm for s-polarized light. We believe that this is the highest value reported to date for thick LB films.