Periodic Reporting for period 2 - PEM-SPrint (Polymeric Electromagnetic Metamaterials created by flow-induced Structure PRINTing)
Reporting period: 2022-08-01 to 2024-01-31
The increasing miniaturization and integration of numerous components in electronic devices and the booming use of wireless technologies leads to an explosion in the amount of electromagnetic waves and resulting crosstalk. In addition, with the recent 5G mobile network, a major challenge is to enhance the range of the electromagnetic waves, which could be accomplished by suitable wave bending around obstacles. To make these upcoming technologies viable for the future, a novel class of materials is needed. These materials need to fulfil two major requirements namely processability into complex and customized shapes and local interactions with selected electromagnetic waves. The aim of this research is to develop polymeric multi-phasic electromagnetic metamaterials generated by a novel processing method, i.e. flow-induced structure printing. The novel method will make it possible to create 3-dimensional materials having substructures that are up to 100 times smaller than the dimension of the printer nozzle. By using polymeric materials with conductive and magnetic inclusions, 3D structures will be generated that allow to induce electromagnetic metamaterial responses such as wave bending or complete absorption. To enable these groundbreaking developments in material design and processing, fundamental understanding should be generated on the relations between microstructure and electromagnetic properties in 3D structured materials with conductive and magnetic inclusions combined with their flow-induced structure development.
A 2D and 3D finite element model has been developed that allows to predict the electric field distribution and EMI shielding performance of polymer composite shields in a rectangular waveguide and in free space. The shape/geometry and variation of lossy permittivity as a function of three-dimensional space can be arbitrarily selected, allowing to explore metamaterial behaviour of 3D-printed composite shields. This finite element model is validated for limit cases with analytical solutions obtained via transfer-matrix theory. The ability to switch between different boundary conditions (waveguide versus free space) has allowed to investigate the relevance of waveguide measurements for actual shielding applications.
In terms of material characterization, we have developed home-build sample holders and analysis procedures to accurately extract electromagnetic properties of polymer nanocomposites in the GHz region. A careful comparison between various calculation methods has allowed to map out the applicability window of various methods. The validity of the analysis method was verified by the fact that correct predictions of the shielding performance of stacks of uniform polymer nanocomposite layers with 1D variation in permittivity are obtained, based on the properties of the nanocomposite building blocks. Using this methodology, optimal sequences of stacks of building blocks were then developed.
To allow further determination of optimal structures for shielding, an optimization program was also developed based on transfer-matrix theory returning a 1D lossy permittivity distribution in a nanocomposite shield for which shielding effectiveness is maximized with the constraint that shielding is entirely absorption-based within the selected frequency regime. Using the numerical model, this optimization could be extended to shielding performance of unbounded shields. Currently, nanocomposite structures following the designed sequences are being 3D printed. Hereby, it was also found that the printing process itself affects the nanoparticle distribution and orientation, which provides an additional opportunity to steer the material properties. The ratio of absorption to reflection is significantly improved as compared to that of uniform nanocomposite shields.
The production and (rheological and thermal) characterization of different suspensions with conductive and magnetic particles in polymer matrices for 3D printing purposes has been performed. This way, printable suspensions could be selected. Electromagnetic shields were 3D printed. Further modelling is on-going to design more structures to be printed and to gain a better understanding of the relevant parameters that govern the material behaviour. A home-built 3D printing setup has been developed to create multi-material electromagnetic shields.
In terms of material characterization, we have developed home-build sample holders and analysis procedures to accurately extract electromagnetic properties of polymer nanocomposites in the GHz region. A careful comparison between various calculation methods has allowed to map out the applicability window of various methods. The validity of the analysis method was verified by the fact that correct predictions of the shielding performance of stacks of uniform polymer nanocomposite layers with 1D variation in permittivity are obtained, based on the properties of the nanocomposite building blocks. Using this methodology, optimal sequences of stacks of building blocks were then developed.
To allow further determination of optimal structures for shielding, an optimization program was also developed based on transfer-matrix theory returning a 1D lossy permittivity distribution in a nanocomposite shield for which shielding effectiveness is maximized with the constraint that shielding is entirely absorption-based within the selected frequency regime. Using the numerical model, this optimization could be extended to shielding performance of unbounded shields. Currently, nanocomposite structures following the designed sequences are being 3D printed. Hereby, it was also found that the printing process itself affects the nanoparticle distribution and orientation, which provides an additional opportunity to steer the material properties. The ratio of absorption to reflection is significantly improved as compared to that of uniform nanocomposite shields.
The production and (rheological and thermal) characterization of different suspensions with conductive and magnetic particles in polymer matrices for 3D printing purposes has been performed. This way, printable suspensions could be selected. Electromagnetic shields were 3D printed. Further modelling is on-going to design more structures to be printed and to gain a better understanding of the relevant parameters that govern the material behaviour. A home-built 3D printing setup has been developed to create multi-material electromagnetic shields.
The overall objective of the proposed research is to develop polymeric multi-phasic EM metamaterials using several unexplored regions of the design space, namely gradients and anisotropy in 3D inclusion geometries, composition and porosity. To reach this goal, a novel 3D printing methodology, flow-induced structure printing, will be developed. This method will produce hierarchical structures that contain gradients or microscopic substructures within each printed layer of macroscale 3D printed objects. Thereby, the lengthscales of the substructures (micrometer range) will be much smaller than that of the printed layer and the printed macroscale object. This will be made possible by introducing static mixers designed for flow-induced structuring in the nozzle of an extrusion-based printer. Fundamental studies of the flow-induced structuring process and the roles of rheology and interfacial dynamics in this process will lead to deeper understanding of the relationships between the flow properties and resulting micro-structures within 3D printed macro-objects. Thereby, innovative static mixer designs will be developed to generate novel substructure geometries. Hence, hierarchically structured materials with target shapes can be generated with one continuous production process. The main goals of the proposed research are:
- a modelling framework that constitutes a rational design strategy for multi-phasic EM metamaterials for different applications focussing on generating novel geometries that exploit the 3rd dimension (WP1)
- fundamental understanding of the relations between geometrical and compositional parameters of the EM metamaterials and their EM behaviour (WP1 and WP5)
- fundamental understanding of the flow-microstructure-dielectric/magnetic properties relations for suspensions with magnetic and conductive particles (WP2)
- fundamental understanding of the stability of interfaces (with or without complex rheology in the bulk and at the interface) in different flow conditions (WP3)
- a methodology for flow-induced structuring and subsequently flow-induced structure printing of suspensions containing conductive and/or magnetic particles and using novel approaches to reach small length scales within large structures (WP2, WP3 and WP4)
- polymeric multi-phasic electromagnetic metamaterials with hierarchical structures and gradients in composition, microstructure and porosity (WP2, WP3, WP4 and WP5)
- a modelling framework that constitutes a rational design strategy for multi-phasic EM metamaterials for different applications focussing on generating novel geometries that exploit the 3rd dimension (WP1)
- fundamental understanding of the relations between geometrical and compositional parameters of the EM metamaterials and their EM behaviour (WP1 and WP5)
- fundamental understanding of the flow-microstructure-dielectric/magnetic properties relations for suspensions with magnetic and conductive particles (WP2)
- fundamental understanding of the stability of interfaces (with or without complex rheology in the bulk and at the interface) in different flow conditions (WP3)
- a methodology for flow-induced structuring and subsequently flow-induced structure printing of suspensions containing conductive and/or magnetic particles and using novel approaches to reach small length scales within large structures (WP2, WP3 and WP4)
- polymeric multi-phasic electromagnetic metamaterials with hierarchical structures and gradients in composition, microstructure and porosity (WP2, WP3, WP4 and WP5)