4PI Two-photon Lithography for Isotropic 3D Nanostructure Fabrication

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Optical lithography is a process that utilises light to define a specific pattern within a material. Standard optical lithography is capable of patterning materials in two dimensions and the possible feature size scales with the wavelength of the light. It is research into this process and associated techniques that has been one of the main drivers of the technological revolution, is partly responsible for the reduction of areal density within computer hard drives and the doubling of processor power every 18 months (Moore's Law).As we progress through the 21st century it is likely that 3D architectures on the nanoscale will become important in developing advanced materials for future data processing and storage technologies. Two-photon lithography is a 3D fabrication methodology that has recently been commercialised and is having a huge impact upon science, allowing the fabrication of bespoke 3D geometries on a length-scale of 200nm horizontally and 500nm vertically. Commercial two-photon lithography has made the fabrication of 3D systems on the several-100nm scale accessible to scientists in a variety of fields allowing the realisation of swimming micro-robots for targeted drug delivery, bioscaffolds and a range of photonic and mechanical metamaterials. A significant setback with two-photon lithography is the asymmetry in the lateral and vertical resolution, which limits both the absolute size and the type of geometry that can be realised. In this proposal, we are going to utilise our world-leading expertise in non-linear microscopy to modify a commercial two-photon lithography system and obtain enhanced resolution. We will utilise techniques that have already significantly improved the resolution in fluorescence microscopy in order to achieve a 100nm isotropic resolution. The newly built system will be used by our team to fabricate two types of 3D nanoscale magnetic materials, in geometries and on length-scales that are difficult to achieve using other fabrication methodologies. Our work in this area will pave the way for next generation 3D memory technolgies such as magnetic racetrack memory and help us to understand magnetic charge transport in novel magnetic materials. In addition, we will be working with project partners in the regenerative medicine and photonics communities in order to realise a number of novel 3D nanostructured materials. Firstly, we will work with stem cell researchers in order to fabricate artificial tissues that will be used in stem cell differentiation experiments. Our work here will provide a fascinating insight into the role of nanoscale topography upon stem cell differentiation and may eventually have applications in tissue/organ growth. Secondly, we will work with academics studying photonic crystals - artificial materials that are capable of blocking electromagnetic radiation within a certain range of the spectrum. The majority of 3D photonic crystals that have been made to date are capable of attenuating electromagnetic waves that are outside the visible range of the spectrum, limiting applications in optoelectronics. Our work here will allow the fabrication and measurement of photonic crystals that can be used with visible and infra-red light. This work may pave the way to next generation three-dimensional optical circuits that can be utilised by telecommunication industries.Overall, this project will build an internationally unique instrument and utilise it to fabricate a range of advanced materials. This will put the U.K. at the forefront of 3D lithography technologies and the associated biomedical, magnetic and photonic materials that will be realised using our newly built instrument.