Congress contributions

The manufacturing of optical freeform surfaces offers a high potential for optical approaches in the future, since they can make new optical systems lighter and more compact or even enable completely new functions, compared to conventional optics. However, the expanded possibilities go hand in hand with higher complexity in production of freeforms for precision optical applications. This leads to high prices and long delivery times. This paper shows an approach to improve manufacturing of freeforms in small batch sizes with a high degree of customization, by a process chain consisting of (ultrasonic-assisted) pre- and fine grinding combined with ultra-fine grinding using resin bond tools. The process chain is suited for efficient fabrication of optical surfaces. A main focus of the experiments is on reduction of low- and mid-spatial frequency surface deviations, as well as surface roughness. Several different influencing factors in a 5-axis CNC grinding process of fused silica freeforms are investigated and their effects on the resulting surface topography (from the low to the high frequency range of surface deviations) are observed using white light interferometry measurement principles. Various optimization approaches can be concluded.

Hysteresis response of epitaxially grown graphene nanoribbons devices on semi-insulating 4H-SiC in the armchair and zigzag directions is evaluated and studied. The influence of the orientation of fabrication and dimensions of graphene nanoribbons on the hysteresis effect reveals the metallic and semiconducting nature graphene nanoribbons. The hysteresis response of armchair based graphene nanoribbon side gate and top gated devices implies the influence of gate field electric strength and the contribution of surface traps, adsorbents, and initial defects on graphene as the primary sources of hysteresis. Additionally, passivation with AlOx and top gate modulation decreased the hysteresis and improved the current-voltage characteristics.

We report the first observation of optical near-field coupling to an ultrafast wavepacket of free, low-energy electrons. Transient optical near-fields, highly spatially confined around a nanometer-sized Yagi-Uda-antenna are probed in a point-projection-microscope with 30-fs resolution.

Although several methods are developed for estimating the state of charge of lithium-ion batteries, there is still a challenge regarding monitoring the second life of these batteries due to the expected difference in the behavior and operating conditions in their second life. Considering that each method has its advantages and disadvantages according to the application and operating conditions, and monitoring the batteries in their second life is of special importance because it is required to integrate with the battery management system to balance cells, diagnose faults and prevent overheating. Therefore, the estimation method developed in this study, by incorporating artificial neural network method and Kalman filter method with fine-tuning of the filtering process using Coulomb counting, provides a solution for more accurate online monitoring of these batteries. Aiming to get the best possible performance, considering the specificity of the second life of the batteries in terms of operating voltage, low values of expected capacity, discharge ratio and other operational parameters.

Modern dielectrophoresis (DEP)-based microchips permit the isolation of pure single cells from heterogeneous cell mixtures. However, sorting throughputs and sample loading capacities are limited and active on-chip circuitry keeps the costs per sorted cell comparatively high. To overcome these problems, we have developed a novel DEP sorter consisting of a three-metal-layer microwell array. The entirely passive architecture of our device allows for inexpensive fabrication and universal sample input volumes. Nonetheless, experimental results revealed that our prototype exceeds the sorting speed of commercially available DEP sorters by at least one order of magnitude while maintaining single-cell precision and avoiding physical cell contact.