Research laboratory for additive manufacturing of soft morphing materials

Introduction

Our laboratory focuses on research of novel shape-memory and shape-shifting soft materials and their transfer to additive manufacturing processes. Current smart materials, i.e. materials whose shape changes with an external trigger, such as with temperature change or light irradiation, rely mostly on mechanical manipulation as the means of programing their shape and, simultaneously, the direction of deformation. This restricts the material to thin strip-shaped geometries with unidirectional shape changes. While synthesis procedures for imprinting complex deformation configurations do exist (e.g. crosslinking under modulated or polarized light), the material geometries are again limited only to thin films or micron-sized specimens. In order to achieve morphing into three dimensions, such materials depend on origami-like bending from a 2D film into a 3D object with empty volume. The utilization of soft shape-memory materials in commercial applications and processes have been therefore greatly hindered by their non-practical synthetisation methods.

Our team have made a step in overcoming this problem by developing a soft-soft composite material consisting of magnetically oriented liquid crystal elastomer particles dispersed in a cured polymer matrix, which we termed Polymer-dispersed liquid crystal elastomers or PDLCEs. Such material can be moulded into arbitrary shapes and sizes, and it’s morphing configurations imprinted by spatially modulating the direction of deformation across the material using an aligning magnetic (or electric) field. The result is a soft, thermomechanically active elastic material with reversible shape change. In addition to this, the material also exhibits shape-memory abilities – it can be reshaped into a new form, from which it recovers when heated.

The lack of mechanical manipulation of the specimen and the liquid nature of the pre-polymerized PDLCE melt makes the material well suited for implementation into additive manufacturing techniques. Our current research deals with the development of a PDLCE printable ink and has already led us to creating a straightforward process of producing a PDLCE polymer suspension consisting of anisotropically shaped microparticles, achieved by thermal-cycling and mechanical shearing the suspension. Such particles can be aligned with simple shear-flow, thus eliminating the need for external alignment fields to imprint thermomechanical deformity into the system. This makes the PDLCE material print-ready with extrusion based 3D printers, the realization of which is our next step.

In addition to the current development and research of PDLCEs, our laboratory focuses on thermomechanical characterization and NMR spectroscopy and relaxometry of materials, especially on ²H-NMR spectroscopy used for studies of dynamical and ordering processes in liquid crystal based systems.