A new class of liquid-crystal resins will let researchers print 3D microstructures whose mechanical, optical, and electrical properties vary by direction—like wood grain, but at scales smaller than a human hair. Conventional 3D printing at micrometre resolution produces materials with uniform properties in every direction. That limits what engineers can build. Many useful devices—from polarising optics to lightweight structural parts—require materials that are stiff in one direction and flexible in another, or that transmit light differently depending on orientation. Until now, no printing resin could deliver that control at such fine scales. If the team succeeds, manufacturers could print switchable optical components that steer light without complex electronics, or mechanical metamaterials that are both strong and ultralight. These would improve communications devices, medical instruments, and aerospace components—systems most people never see but rely on daily. The project is fundamentally about expanding what is possible in additive manufacturing. It does not promise a specific product. But past fundamental work on liquid crystals gave us flat-panel displays; this work could similarly unlock a new generation of micro-printed functional parts.
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Three-dimensional (3D) additive manufacturing is revolutionising industry, enabling the rapid manufacture of new sophisticated components with reduced material waste. Two photon polymerisation offers exciting prospects for additive manufacturing at high 3D resolution with feature sizes below a thousandth of a millimetre. Traditional two photon polymerisation writes structures into a resin which exhibit isotropic material properties. In this project, we expand the functionality window for two photon polymerisation by generating a new class of stimuli-responsive liquid crystalline (LC) resins with as yet unrealised optical/electronic/mechanical functionality. This creates many new design possibilities when fabricating devices for optical, mechanical and biomedical applications. The LC resin is characterised by a director field, which denotes a particular direction within the resin that has different optical, electrical, and mechanical properties to all other directions. When the resin undergoes photopolymerisation, the ensuing polymer structure also exhibits anisotropic properties which correlates with that of the initial resin director field. The resin director field can be controlled during fabrication by applying electrical, optical or flow fields. Thus, it is possible to generate microscale polymer structures with spatially variant tailored anisotropic material properties in 3D. To harness the exciting possibilities of this new fabrication landscape, material development work is urgently needed to characterise and optimise both the resin and the resulting 3D polymer micro-structures. These challenges will be addressed using complementary research expertise from teams at the University of Oxford, UK and Osaka University, Japan to give a collaborative program of research with mutually beneficial knowledge transfer with the potential for significant impact in the broad and intersecting fields encompassing LC, polymer, and soft material development. The key aims of the project are: Develop a materials toolkit that can be used to determine the optimum LC-polymer resin for different end-user applications. Use high resolution 3D microscopy to accurately characterise the anisotroptic properties of the fabricated 3D polymer structures at the microscale, giving the required feedback to direct the materials optimisation. Understand how the optically initiated polymerisation process influences polymer formation and diffusion properties. Showcase the new materials developments in chosen application areas. Materials optimisation will be carried out by considering different constituent LC precursors, with varying amounts of reactive mesogen (using blends of monoacrylates and diacrylates) and photoinitiator. Additional dopants will be introduced to further extend material capabilities. Differences between one photon and two photon polymerisation will be explored and how the choice of photoinitiator affects resolution and specificity of the fabricated polymer structures. Adaptive optical techniques will be developed to tailor the light field at the point of polymerisation, to ensure optimum optical resolution and polarisation control. Raman and Brillouin spectroscopy will be used for microscale characterisation of polymer material properties, and will be integrated into the fabrication system to give in-situ feedback for accurate control over the polymerisation activation rate and rapid optimisation. The materials development program promises polymer structures printed at micrometre scale resolution with tailored anisotropy in the mechanical, optical and dielectric properties. This is destined to feed into many new device applications, some of which will be explored as part of the project to generate further impact. In particular, we will target switchable and tuneable optical devices that provide intricate control over incident light but without the need for complex drive electronics, and mechanical metamaterials for low density lightweight functional parts.
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