Marta M. D. Ramos

Modeling of the human enamel laser ablation process at the mesoscopic scale

A mesoscopic simulation of the process of human enamel laser ablation by Er:YAG and CO2 lasers is being developed using the finite element method, taking into account the complex structure and chemical composition of this material. A geometric model that allows studying in detail the temperature, stress and displacement distribution within a few enamel rods is presented. The heat generation that takes place inside the enamel at the centre of the laser spot, caused by a non-ablative laser pulse emitted by CO2 and Er:YAG lasers, was simulated. The sensitivity of our model to the estimated material parameters was studied. Temperature, displacement and stress distribution maps obtained for both lasers are presented. These preliminary results suggest that the temperature distribution across the enamel rods is different in the two situations considered; thermally induced stresses in the material are higher in the regions that are richer in hydroxyapatite (HA), and the higher displacements are observed in the regions that are rich in water. The rod tails inside enamel present higher stresses in the direction perpendicular to the surface of enamel than the ones that are created at the surface of our simulated structure. We conclude that the mesostructure plays a crucial role in the accurate modelling of dental laser ablation.

Multi-scale modelling of polymer-based optoelectronic devices

The optimization of polymer-based optoelectronic devices such as light-emitting diodes (LEDs), photodetectors and photovoltaic cells requires the understanding how molecular properties and the spatial arrangement of the conjugated strands affect the electronic processes underlying the functioning of these devices. Since some of the important features are determined largely by the individual molecular strands and other features depend strongly on the nanostructure, a multi-scale modelling of materials and device properties is needed. In this work we discuss the atomistic and nanoscale modelling of charge injection, transport and trapping single-carrier diode based on poly(p-phenylene venylene) (PPV), which also applies to other optoelectronic devices.