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Item type:Publication, Access status: with files , Electrical and morphological properties of tollens-deposited silver on photopolymer resin relevant to 3D-printed microwave componentsThis work presents the first systematic investigation of the fundamental electrical and morphological properties of Tollens-deposited silver on stereolithography (SLA) 3D-printed polymers. Instead of examining specific waveguides or components, the goal is to establish reliable superordinate process-property relationships for the Tollens-based metallization. Therefore, planar specimens were fabricated to allow quantitative characterization of the metallization. Fundamental process parameters: immersion time, temperature, surface cleaning, and surface pretreatment were systematically varied, and additional influencing factors including ultrasonic assistance, water purity, surface contamination, and repeated metallization were assessed. The characterization included measurements of layer thickness, electrical conductivity, sheet resistance, surface roughness, as well as morphological analysis by scanning electron microscopy and optical microscopy. Depending on the combination of process parameters, the conductivity and layer thickness show significant variations from 27.9 to 6.6 MS/m and 164 to 77 nm, respectively. The best result for a single metallization, 27.9 MS/m and 164 nm, was achieved using deionized water and ultrasonic assistance. The deposited silver thickness is markedly smaller than the surface roughness, and the silver layer is overlain by an island-like layer of irregular silver agglomerates, resulting in an atypical multilayer structure. The findings of this work establish a quantitative basis for the future assessment and optimization of loss and propagation characteristics in microwave components based on 3D-printed, Tollens-metallized photopolymers.Publicationtype: Journal Article23 2 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Micrometer Sensing With Microwaves: Precise Radar Systems for Innovative Measurement Applications(2021-01-01); ; ; ; Radar sensors have been widely used to estimate speed and displacement of remote targets. A novel market for contactless radar sensing is emerging in the field of automatization and process analysis, where non destructive testing and evaluation methods are desired. Here, modern radar systems offer various advantages over conventional sensors since they enable the contactless, continuous, and cost-efficient measurement of static or dynamic ranges. These can further be used for vibration and vital sign characterization. Advances in microwave technology, an increasing integration density, and the development of novel algorithms keep boosting the performance of the systems. After introducing the most common operation principles, such as unmodulated and frequency-modulated continuous-wave radar, different design aspects and building blocks of cutting-edge systems are explained in detail. In the second part, selected applications are described in detail. These include the sheet thickness monitoring of metallic foils, and the measurement of the ground speed of vehicles with the latest approaches. Exemplary low-power radar systems are presented to show the limits in terms of power consumption while still offering a high measurement precision. In addition, the topics of mechanical vibration sensing and vital sign sensing are addressed by introducing tailored systems.Publicationtype: Journal Article51