Planar approach for designing and fabricating active metamaterials

Abstract

Shape changing active metamaterial could form the structural backbone of an object as well as deliver the actuation. The integration of these two functions saves design space and allows for creative topologies. The literature study of this thesis investigated smart material actuator solutions that could be used to enable such active metamaterials, covering PVDF, dielectric elastomers, IPMC, conducting polymer, carbon nanotubes and piezoelectric ceramics. It is found that dielectric elastomers achieve high strains, low stress and need high driving voltages. Conducting polymers are able to deliver both high stress and high strain, but consume relatively much power. If power consumption is a priority, Electronic EAPs are preferred. PVDF does not excel on stress or strain, but is an overall good performer. The outlook of realizing active metamaterials via integration of actuation paves the way for non-rigid body deformations and broadens the view on potential applications. At the moment such a system cannot be realized due to the lack of appropriate designs and manufacturing methods. The objectives of this report are (1) the employment of smart materials to make metamaterials active, (2) proposing a method of how to realize this using production materials and (3) employing these methods to build a small metamaterial demonstrator that functions both as the actuator and the structure. In this work this was done by designing and constructing a tube shaped metamaterial demonstrator of a high precision positioning system. The 3D geometry of the metamaterial was built by layering planar pre-fabricated structures which use smart material for actuation. The design of the unit cells can be implemented in metamaterial of any shape and allows for miniaturization, which extends its applicability. The metamaterial was capable of vertical displacements. The constructed metamaterial tube was able to bend itself. Measured maximum amplitudes of a single layer, and the three layered stack were respectively 4.60 μm and 6.91 μm. Roll movement of the top layer of the stack was achieved with a lowest point of -0.13 μm and a highest point of 8.49 μm. The system showed that smart materials are a suitable choice to make metamaterial active, and that active metamaterial could be produced using production material. The planar approach for design and fabrication, provides a relatively simple and fast method for building metamaterial in general.