Three dimensional (3D) bioprinting of multiple cell types within optimised extracellular matrices has the potential to more closely model the 3D environment of human physiology and disease than current alternatives. In this study, we used a multi-nozzle extrusion bioprinter to establish models of glioblastoma made up of cancer and stromal cells printed within matrices comprised of alginate modified with RGDS cell adhesion peptides, hyaluronic acid and collagen-1. Methods were developed using U87MG glioblastoma cells and MM6 monocyte/macrophages, whilst more disease relevant constructs contained glioblastoma stem cells (GSCs), co-printed with glioma associated stromal cells (GASCs) and microglia. Printing parameters were optimised to promote cell-cell interaction, avoiding the 'caging in' of cells due to overly dense cross-linking. Such printing had a negligible effect on cell viability, and cells retained robust metabolic activity and proliferation. Alginate gels allowed the rapid recovery of printed cell protein and RNA, and fluorescent reporters provided analysis of protein kinase activation at the single cell level within printed constructs. GSCs showed more resistance to chemotherapeutic drugs in 3D printed tumour constructs compared to 2D monolayer cultures, reflecting the clinical situation. In summary, a novel 3D bioprinting strategy is developed which allows control over the spatial organisation of tumour constructs for pre-clinical drug sensitivity testing and studies of the tumour microenvironment.

To construct PSOEs, two anisotropic substrates [ 7,8 ] or a structure with form-birefringent [ 9,10 ] have been traditionally used to impose the desired phase delay for the two cross-polarizations of incident light. Although these devices prove to be effective, it is challenging for the etching depth control especially when some extreme phase profi les are needed. Besides, these devices suffer from the limited phase levels and the large pixel size due to the current fabrication techniques.Benefi ting from the easy fabrication and the fl exible control of the light propagation, metasurfaces have provided new opportunities to realize virtually fl at optics. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] In comparison with the traditional PSOEs, which realize the birefringence by carefully designing the structure of each pixel, the metasurface provides a much easier way by directly merging different optical elements together with each one working for a particular incident polarization. Refl ective-type metasurface holograms have been demonstrated to reconstruct two interchangeable images [ 27,28 ] by controlling the linear polarization state of the incident light. Although the previously proposed metasurfaces have shown their unique advantages such as broadband [ 27 ] and wide fi eld of view, [ 28 ] further application is hindered by the limited phase levels [ 27 ] and binary modulation [ 28 ] of the holograms since most optical elements such as a lens or an axicon are required to precisely manipulate the phase of the wavefront.Driven by miniaturization and system integration, ultrathin, multifunction optical elements are urgently needed. Traditional polarization-selective optical elements are mainly based on birefringence, which is realized by using the well-designed structure of each phase pixel. However, further reduction of the pixel size and improvement of the phase levels are hindered by the complicated fabrication process. An approach is proposed to realize a metasurface device that possesses two distinct functionalities. The designed metasurface device, consisting of gold nanorods with spatially varying orientation, has been experimentally demonstrated to function as either a lens or a hologram, depending on the helicity of the incident light. As the phase of the scattered light is controlled by the orientation of the nanorods, arbitrary phase levels and dispersionless phase profi le can be realized through a much simpler fabrication process than the conventional device. This approach provides an unconventional alternative to realize multifunction optical element, dramatically increasing the functionality density of the optical systems.

A metasurface can manipulate light in a desirable manner by imparting local and space-variant abrupt phase change. Benefiting from such an unprecedented capability, the conventional concept of what constitutes an optical lens continues to evolve. Ultrathin optical metasurface lenses have been demonstrated based on various nanoantennas such as V-shape structures, nanorods and nanoslits. A single device that can integrate two different types of lenses and polarities is desirable for system integration and device miniaturization. We experimentally demonstrate such an ultrathin metasurface lens that can function either as a spherical lens or a cylindrical lens, depending on the helicity of the incident light. Helicity-controllable focal line and focal point in the real focal plane, as well as imaging and 1D/2D Fourier transforms, are observed on the same lens. Our work provides a unique tool for polarization imaging, image processing and particle trapping.

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