Tamper-proof markings for the identification and traceability of high-value metal goods.

A customized UV nanosecond pulsed laser system has been developed for the fast generation of tamper-proof security markings on the surface of metals, such as stainless steel, nickel, brass, and nickel-chromium (Inconel) alloys. The markings in the form of reflective phase holographic structures are generated using a laser microsculpting process that involves laser-induced local melting and vaporization of the metal surface. The holographic structures are formed from an array of optically-smooth craters whose depth can be controlled with ± 25nm accuracy. In contrast to conventional security markings, e.g., engraved serial numbers, etched part numbers and embossed polymer holographic stickers, which are only attached to the metal products as an adhesive tape, the phase holographic structures are robust to local damage (e.g. scratches) and resistant to tampering because they are generated directly on the metal surface. This paper describes a novel laser-based process for security marking of high-value metal goods, investigates the optical performance of the holographic structures, and demonstrates their application to watches.

Direct CO(2) laser-based generation of holographic structures on the surface of glass.

A customized CO(2) laser micromachining system was used for the generation of phase holographic structures directly on the surface of fused silica (HPFS(®)7980 Corning) and Borofloat(®)33 (Schott AG) glass. This process used pulses of duration 10µs and nominal wavelength 10.59µm. The pulse energy delivered to the glass workpiece was controlled by an acousto-optic modulator. The laser-generated structures were optically smooth and crack free. We demonstrated their use as diffractive optical elements (DOEs), which could be exploited as anti-counterfeiting markings embedded into valuable glass-made components and products.

A Bioprinted Heart-on-a-Chip with Human Pluripotent Stem Cell-Derived Cardiomyocytes for Drug Evaluation.

In this work, we show that valve-based bioprinting induces no measurable detrimental effects on human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The aim of the current study was three-fold: first, to assess the response of hiPSC-CMs to several hydrogel formulations by measuring electrophysiological function; second, to customise a new microvalve-based cell printing mechanism in order to deliver hiPSC-CMs suspensions, and third, to compare the traditional manual pipetting cell-culture method and cardiomyocytes dispensed with the bioprinter. To achieve the first and third objectives, iCell2 (Cellular Dynamics International) hiPSC-CMs were used. The effects of well-known drugs were tested on iCell2 cultured by manual pipetting and bioprinting. Despite the results showing that hydrogels and their cross-linkers significantly reduced the electrophysiological performance of the cells compared with those cultured on fibronectin, the bio-ink droplets containing a liquid suspension of live cardiomyocytes proved to be an alternative to standard manual handling and could reduce the number of cells required for drug testing, with no significant differences in drug-sensitivity between both approaches. These results provide a basis for the development of a novel bioprinter with nanolitre resolution to decrease the required number of cells and to automate the cell plating process.

Three dimensional in vitro models of cancer: Bioprinting multilineage glioblastoma models.

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.

Multifunctional metasurface lens for imaging and Fourier transform.

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.