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Pre-stretching membranes in dielectric elastomer actuator (DEA) systems is a widely known technique to improve the dielectric's breakdown strength and therefore enhance the overall device performance. The impact of this approach on the long-term reliability of DEAs is, however, still unknown. In the present work, it is investigated how the elastomer lifetime is affected by the mechanical pre-stretch. Silicone membrane samples with different pre-stretch ratios were prepared and the respective DC dielectric strengths were measured for both short and prolonged tests using methodologies inherited from high voltage assessment technology. It is shown that, despite an absolute beneficial increase of the dielectric strength for the tensioned membranes, pre-stretching has a detrimental effect on the system's useful life. In all the studied cases, the pre-stretched specimens showed a shorter expected lifetime compared to new, relaxed membranes. The results suggest a careful selection of the relative electric field to be applied to DEAs system for long and reliable lifetime.

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Film pre-stretching is a widely adopted solution to improve dielectric strength of the DEA systems. However, to date, long term reliability of this solution has not been investigated. In this work it is explored how the dielectric elastomer lifetime is affected by film pre-stretching. The dielectric loss of soft polydimethylsiloxane (PDMS) films is studied for different stretch ratios by measuring tanδ. Additionally, time-to-breakdown was measured at DC electric stress for different stretch ratios. For this purpose, accelerated life test (ALT) were performed. The results obtained are compared with non-pre-stretched samples. This study suggests that no additional dielectric losses are caused by film stretching up to 80% of original dimensions.

In electrostatic charged particle lens design, optimization of a multi-electrode lens with many free optimization parameters is still quite a challenge. A fully automated optimization routine is not yet available, mainly because the lens potential calculations are often done with very time-consuming methods that require meshing of the lens space. A new method is proposed that improves on the low speed of the potential calculation while keeping the high accuracy of the mesh-based calculation methods. This is done by first using a fast potential calculation based on the so-called Second-Order Electrode Method (SOEM), at the cost of losing some accuracy, and then using a Genetic Algorithm (GA) for the optimization. Then, by using the parameters of the approximate systems found from this optimization based on SOEM, an accurate GA optimization routine is performed based on potential calculation with the commercial finite element package COMSOL. A six-electrode electrostatic lens was optimized accurately within a few hours, using all lens dimensions and electrode voltages as free parameters and the focus position and maximum allowable electric fields between electrodes as constraints.