3D printing and properties of multi-material structures and devices

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3D printing and additive manufacturing has matured rapidly in the last decade for the direct production of shaped components made from metallic alloys, ceramics, polymers and biomaterials. In some cases, commercial products have been brought to market successfully on the basis of novel geometries or reduced number of manufacturing steps enabled by additive manufacture (AM). But in many cases existing technologies continue to deliver components with sufficient performance at significant lower unit cost that AM. More recently, higher added value AM components comprising multi-materials manufactured in a single operation by additive manufacture have started to be explored. These developments have been enabled by a wider range of affordable additive manufacturing techniques and an ever-widening palette of printable materials. Unlike mono-material components, these single-step multi-material components and devices can offer both faster manufacturing, and in some case, new functionalities.We have developed and exploited new multi-material approaches to form functional devices for use in the telecommunications sector, including graded index microwave lenses, spiral phase plates and dielectric origami for antenna tuning. We have also printed resonating meta-materials - artificial materials that have properties unavailable from single material classes.This project aims to identify and exploit new and previously unexplored processing approaches to build dielectric materials, including meta-materials, with graded or periodic dielectric properties using single-step, multi-material printing. The project will involve the modification of printers by the addition of new deposition heads, and software modifications as needed. The way different materials interact dynamically in the build process as they are co-deposited will be studied to understand how visco-elastic or rheological properties, temperature, surface tension, etc. affect the final quality (defects, porosity, tolerance, surface finish, etc.) of the multi-material build. Because multi-material fabrication opens up a wide design space, numerical simulation of potential designs is an essential component of the research, and will be undertaken using CST, Comsol and other commercial codes. Parametric simulation studies will be undertaken to assess the influence of material arrangements and geometry on key properties such as microwave gain, directivity and far-field behaviour of various simple optic-like devices. Having simulated and then built multi-material assemblies according to optimised designs, the devices will be assessed by a range of techniques including microstructural assessment by various microscopies and X-ray microtomography, and mechanical testing (for example in the case of mechanically actuated dielectric origami). Far field microwave measurements in an anechoic chamber, in collaboration with the Department of Engineering Science, will also be used to reconcile design and simulated performance with performance in practice, and will allow model validation and an understanding of the influence of manufacturing defects on device performance. In certain cases, we will also develop bespoke printable materials, for example where specific values of permittivity or permeability are required. This project falls within the EPSRC (i) information and communication technologies, and (ii) manufacturing the future research areas.