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The stringent and conflicting requirements imposed on optomechanical instruments and the ever-increasing need for higher resolution and quality imagery demands a tightly integrated system design approach. Our aim is to drive the thermomechanical design of multiple components through the optical performance of the complete system. To this end, we propose a new method combining structural-thermal-optical performance analysis and topology optimization while taking into account both component and system level constraints. A 2D two-mirror example demonstrates that the proposed approach is able to improve the system’s spot size error by 95% compared to uncoupled system optimization while satisfying equivalent constraints., Structural Optimization and Mechanics

The stringent and conflicting requirements imposed on optomechanical instruments and the ever-increasing need for higher resolution and quality imagery demands a tightly integrated system design approach. Our aim is to drive the thermomechanical design of multiple components through the optical performance of the complete system. To this end, we propose a new method combining structural-thermal-optical performance analysis and topology optimization while taking into account both component and system level constraints. A 2D two-mirror example demonstrates that the proposed approach is able to improve the system’s spot size error by 95% compared to uncoupled system optimization while satisfying equivalent constraints., Computational Design and Mechanics

Digital Micromirror Device (DMD)-based grayscale lithography is a promising tool for three dimensional (3D) microstructuring of thick-film photoresist since it is a maskless process, provides possibility for the free-form of 3D microstructures, and therefore rapid and cost-effective microfabrication. However, process parameter determination lacks efficient optimization tool, and thus conventional look-up table (indicating the relationship between development depth and exposure dose value under a fixed development time) approach with manual try-and-error adjustment is still gold standard. In this paper, we firstly present a complete “input target-output parameters” single exposure optimization method for 3D microstructuring utilizing DMD-based grayscale lithography. This numerical optimization based on lithography simulation and sensitivity analysis can automatically optimize a combination of three process parameters for target microstructure; exposure dose pattern, a focal position, and development time. Through a series of experiments using a 20 μm thick positive photoresist, validity of the proposed optimization approach has been successfully verified. Secondly, with the purpose of further advancing accuracy and improve the uniformity of precision for the target area, a multiple exposure optimization method is proposed. The simulated results proved that the multiple exposure optimization method is a promising strategy to further improve precision for thicker photoresist structure., Structural Optimization and Mechanics

We report a multiple patterning approach utilizing digital-micromirror-device (DMD)-based grayscale lithography, providing a solution to improve fabrication accuracy for entire target three-dimensional structure. Because DMD-based lithography system consists a projection lens system, better resolution can be obtained around focal position comparing to the outer region of depth of focus. Thus, for thick-film resist micro structuring, exposing with multiple focal positions with separate grayscale masks leads to improvement of fabrication accuracy. In order to find the best combination of the multiple focal positions and their grayscale masks, the computational optimization is combined to the multiple patterning approach. Through a several experiments, effectiveness of the proposed approach was successfully demonstrated., Structural Optimization and Mechanics

Reducing weight of off-shore wind turbine nacelles is currently a key driver of innovation within the wind turbine industry. Weight reduction will not only lead to smaller loads and thus smaller towers of the turbine, but also reduce logistic costs during the turbine’s installation. This holds even more so for off-shore turbines, the costs related to installing a turbine is a substantial investment compared to the operational cost. A reduced nacelle weight will, subsequently, lead to reduced cost of wind energy. For direct-drive turbines, the generator is one of the heaviest parts of the wind turbine nacelle. Due to the low rotational speed of the generator, the loads are especially high in this type of turbine, which increases the necessary structural mass of the rotor. Recently, designed flexibility has been identified as one approach to achieve weight reduction. However, reducing the weight of the support structure has proven difficult, due to the complex pattern of dynamic excitation forces. Until now, density based topology optimisation has hardly been employed for the design of wind turbine parts. This publication investigates the possible weight reduction which results from applying this method to the support structure of the generator rotor. As a first step, crucial excitation frequencies and spatial force distributions that are generated by the magnetic field are presented. Then the topology optimisation is executed using a modal and a harmonic approach, applying the identified force distributions., Precision and Microsystems Engineering, Mechanical, Maritime and Materials Engineering

We report a multiple patterning approach utilizing digital-micromirror-device (DMD)-based grayscale lithography, providing a solution to improve fabrication accuracy for entire target three-dimensional structure. Because DMD-based lithography system consists a projection lens system, better resolution can be obtained around focal position comparing to the outer region of depth of focus. Thus, for thick-film resist micro structuring, exposing with multiple focal positions with separate grayscale masks leads to improvement of fabrication accuracy. In order to find the best combination of the multiple focal positions and their grayscale masks, the computational optimization is combined to the multiple patterning approach. Through a several experiments, effectiveness of the proposed approach was successfully demonstrated., Computational Design and Mechanics

Reducing weight of off-shore wind turbine nacelles is currently a key driver of innovation within the wind turbine industry. Weight reduction will not only lead to smaller loads and thus smaller towers of the turbine, but also reduce logistic costs during the turbine’s installation. This holds even more so for off-shore turbines, the costs related to installing a turbine is a substantial investment compared to the operational cost. A reduced nacelle weight will, subsequently, lead to reduced cost of wind energy. For direct-drive turbines, the generator is one of the heaviest parts of the wind turbine nacelle. Due to the low rotational speed of the generator, the loads are especially high in this type of turbine, which increases the necessary structural mass of the rotor. Recently, designed flexibility has been identified as one approach to achieve weight reduction. However, reducing the weight of the support structure has proven difficult, due to the complex pattern of dynamic excitation forces. Until now, density based topology optimisation has hardly been employed for the design of wind turbine parts. This publication investigates the possible weight reduction which results from applying this method to the support structure of the generator rotor. As a first step, crucial excitation frequencies and spatial force distributions that are generated by the magnetic field are presented. Then the topology optimisation is executed using a modal and a harmonic approach, applying the identified force distributions., Precision and Microsystems Engineering, Mechanical, Maritime and Materials Engineering

Photolithography is the engineering field where micro-chips are made by creating minuscule patterns on a plate of silicon using light. The patterns are made in a photoactive polymer layer, called a photoresist which was applied to the substrate. These dissolve easily when they are irradiated with light, but resist dissolution during the development process if they were in the shadow. Traditionally, these layers were only a few micrometers thick and only used to create planar patterns. However, recently thick photoresists are getting more attention. In addition, it has also become possible to control the local irradiation accurately enough, such that we can create complex relief-typee3D structures, using grayscale exposure techniques. The potential applications in the field of micro-mechanical devices include micro-sensors and actuators, microoptics and micro-fluidics. Unfortunately, designing the proper light exposure profile and choosing the development time for a specific 3D micro pattern is complicated by the non-linear nature of the processes at hand. Therefore, the most widely used approach is based on trial-and-error designed exposure conditions and manual repair of the design by an engineer. In this research a systematic design approach is developed, based on computational process simulation, associated adjoint sensitivity analysis and optimization techniques. The computationally created designs were fabricated and compared to the desired shape to show the power of this approach., Precision and Microsystems Engineering, Mechanical, Maritime and Materials Engineering

Photolithography is the engineering field where micro-chips are made by creating minuscule patterns on a plate of silicon using light. The patterns are made in a photoactive polymer layer, called a photoresist which was applied to the substrate. These dissolve easily when they are irradiated with light, but resist dissolution during the development process if they were in the shadow. Traditionally, these layers were only a few micrometers thick and only used to create planar patterns. However, recently thick photoresists are getting more attention. In addition, it has also become possible to control the local irradiation accurately enough, such that we can create complex relief-typee3D structures, using grayscale exposure techniques. The potential applications in the field of micro-mechanical devices include micro-sensors and actuators, microoptics and micro-fluidics. Unfortunately, designing the proper light exposure profile and choosing the development time for a specific 3D micro pattern is complicated by the non-linear nature of the processes at hand. Therefore, the most widely used approach is based on trial-and-error designed exposure conditions and manual repair of the design by an engineer. In this research a systematic design approach is developed, based on computational process simulation, associated adjoint sensitivity analysis and optimization techniques. The computationally created designs were fabricated and compared to the desired shape to show the power of this approach., Precision and Microsystems Engineering, Mechanical, Maritime and Materials Engineering