IMp: The customizable LEGO® Pinned Insect Manipulator
Abstract We present a pinned insect manipulator (IMp) constructed of LEGO® building bricks with two axes of movement and two axes of rotation. In addition we present three variants of the IMp to emphasise the modular design, which facilitates resizing to meet the full range of pinned insect specimens, is fully customizable, collapsible, affordable and does not require specialist tools or knowledge to assemble.
Functional differences stabilize beetle communities by weakening interspecific temporal synchrony.
The temporal stability of communities is essential for the maintenance of ecosystem functioning across trophic levels. The stabilizing effect of biodiversity is, among other factors, modulated by the level of synchrony in population fluctuations among the species in the community. What drives community synchrony, however, remains largely unclear. Community synchrony can be affected by external drivers such as disturbances, but also by the properties of the community. Species with different ecological strategies should fluctuate less synchronously than more similar species; thus, an increase in diversity of ecological strategies should decrease synchrony, and increase the stability of the community. Here, using an exceptionally large data set of ground beetle trappings in Dutch heathlands (~370,000 individuals in 19 plots, each sampled between 9 and 36 yr), we assess the drivers of community stability and synchrony, and their relationship with disturbance, species richness, and functional diversity (FD). We found no effect of disturbance (fire and topsoil removal) on community stability or synchrony, probably because of unpredictable patterns of increase or decrease of the populations. Community synchrony was overall positive, giving more support for independent and positive correlation between species than for compensatory dynamics. Synchrony decreased with increasing FD, but not with species richness. Supporting this, we found that the more species pairs differ in their traits, the less synchronously their populations fluctuate, where 74% of all pairs showed no significant correlation. Significant positive synchrony (19% of species pairs) was concentrated among pairs with low trait dissimilarity, and the 7% of pairs with significant negative temporal correlation showed no relation with pairwise functional dissimilarity. The stabilizing effect of FD via decreased synchrony supports largely untested theoretical expectations that an increased diversity of functional strategies in a community will have a stabilizing effect on community abundance. We hypothesize that because competition is low in this community, the stabilizing effect of FD reflects interspecific variation in responses to environmental fluctuations rather than competition.
Adaptive optics for extreme ultraviolet lithography : actuator design and validation for deformable mirror concepts
In the production of integrated circuits (e.g. computer chips), optical lithography is used to transfer a pattern onto a semiconductor substrate (wafer). For lithographic systems using light in the ultraviolet band (EUV) with a 13.5nm nm wavelength, only reflective optics with multi-layers can reflect that light by means of interlayer interference, but these mirrors absorb around 30% of the incident light. Depending on pattern and beam shape, there is a nonuniform light distribution over the surface of the mirrors. This causes temperature gradients and therefore local deformations, due to different thermal expansions. To improve the throughput (wafers per hour), there is a demand to increase the source power, that will increase these deformations even further. Active mirrors are a solution to correct these deformations by reshaping the surface. This thesis addresses the challenges to accurate deform a mirror with high repeatability, meeting the requirements for implementation in a lithographic illumination machine. The main design criteria are vacuum compatibility, actuator stroke and the distance between actuators. Four different experimental mirrors, with increasing complexity, are successfully designed, realized and validated. All mirrors are equipped with thermomechanical actuators to either bend, or axially deform them. These actuators are free from mechanical hysteresis and therefore have a high position resolution with high reproducibility. Extensive finite element analysis is done, to maximize actuator stroke and minimize input power. All mirrors are tested and validated with interferometer surface measurements and thermocouple temperature measurements. The first experimental mirror with one thermo-mechanical bending actuator is successfully built and tested (chapter 2). To obtain a high mirror deflection at a given inserted actuator power, aluminum is chosen as the actuator material. The mirror is made from Zerodur® like the mirrors in the first EUV lithographic demonstration machines. A mirror deformation of 4:7 nm/C is achieved, where the inserted actuator power is 0.044 C/mW, meaning 0:21 nm/mW. The measured characteristic time constant is 10 s, meaning that for a given input, 63% of the steady state stroke is reached within that time scale. All values are close to the predicted ones from the models and also meet the requirements for implementation. To further investigate the concept and to measure the mechanical and thermal actuator coupling, an experimental mirror with four actuators is designed, developed and validated (chapter 3). It is an extension of the mirror with one actuator. In a single actuator step-response, a mirror deflection of 3.4 nm/C is achieved. A design optimization is proposed and successfully tested which reduces the actuator coupling from 30% to 10%, while the mirror deflection at the same input is reduced to 55%. Actuator speed is demonstrated while simultaneously heating all actuators with 3mW, which correspond with a mirror deformation of 33 pm/s. When using an adaptive mirror in an EUV lithography system, actuator strokes of 1 nm/min are required. The demonstrated actuator speed of 33 pm/s = 2 nm/min meets that requirement. The third and fourth mirror have actuators placed perpendicular to the surface (chapter 4). By placing the actuators on a thin back plate, the force loop is localized and therefore a lower actuator coupling is achieved. The results obtained from the third mirror with 7 actuators are close to the predicted values from the static and thermal models. Based on these good results, this actuation principle is implemented in a smaller deformable mirror with 19 actuators inside a 25mm beam diameter. A linear relation between actuator power and temperature of 0.190 C/mW and between power and averaged interactuator stroke of 0.13 nm/mW is achieved. So, the successfully realized mirror deflection is 0:68 nm/ C and no hysteresis is observed. For both mirrors a support frame is developed, that minimizes introduced surface deformations by temperature variations. Thermal step responses are fitted and both heating and cooling characteristic time constants are 2:5 s. The thermal actuator coupling from an energized actuator to its direct neighbor is 6:0, to their neighbors it is 1:3%. The total actuator coupling is approximated around 10%, based on the good agreement between simulated and measured inter-actuator stroke. Finally, chapter 5 summarizes the main findings from the different deformable mirrors and compares them. Also, suggestions for future research are given for implementation into a lithographic machine.