Engineering of a tissue construct that mimics a native tissue’s form and function requires mimicry of the material, chemical, and morphological properties of the target tissue. Matching of these very properties makes fabrication of a composite structure challenging. The authors present a collection of techniques used to create multilayer three-dimensional soft-tissue constructs with high-resolution interlayer registration of individually printed two-dimensional patterns. These techniques include a bioreactor platform integrating NRL’s Biological Laser Printing (BioLPTM) for quick and reproducible printing, culturing, and stacking of individual biopapers. The bioreactors were designed to mount and culture laser machined, stainless steel framed collagen biopapers. The biopapers in turn allowed for handling and high-resolution (<100 μm) registration of otherwise difficult to handle hydrogels. The authors demonstrate printing of endothelial cells onto the biopapers and culturing and tubulogenesis within the bioreactor. They also demonstrate high-resolution interlayer registration of biopapers individually printed with fluorescent beads.
The transfer of laboratory scale solution processing of organic electronics to large area roll-to-roll production requires the use of up-scalable deposition techniques. Furthermore, industrial production demands the omission of halogenated and other harmful solvents. Here, the authors discuss large area inkjet printing using industrial printheads for organic light emitting diodes (OLEDs) or organic photovoltaics (OPVs) applying halogen-free ink formulations. For the inkjet printing of the small molecule OLED emissive layer a low viscosity ink was selected (1.5 mPa s) to obtain layers with outstanding thickness homogeneity. Devices with 3.75 cm2 active area showed a uniform light emission similar to a device with a spin-coated emissive layer. Ink selection for the photo-active layer for OPVs was mostly determined by the device performance and the solubility of the polymer:electron acceptor blend. The inkjet printed layer showed a significant coffee stain effect, which was dependent on the printed layer thickness as well as the printed area. The loss of active material became smaller for larger printed areas. Devices with the inkjet printed photo-active layer from the halogen-free ink showed similar performance to a layer spin-coated from chlorinated solvents. This shows the potential of inkjet printing as a development and production tool for a variety of large area organic electronics.
A lean process route for the contact separation of back-contact solar cells is presented in this article. Inkjet-printing of an etchant is used for patterning Al- and NiV-layers with varying thickness deposited by means of physical vapor deposition (PVD). By adjusting the drop spacing of the droplets, the number of layers printed on top of each other, the temperature during printing and etching, and the etching time, the authors were able to fabricate a meander structure on a silicon wafer with an edge length of 156 mm that was coated with a 100 nm thick NiV-layer. Visual and electrical characterization was performed on test structures. The resistance between these separated structures was up to 1.5 MΩ and thus meets the requirement of a back-contact solar cell.
Color barcodes offer increased density over two-dimensional barcodes, which can be taken advantage of to embed longer data strings in the same printed/displayed area. However, the color channels also offer the possibility of containing multiple, distinct sets of data in the same “hybrid” mark.
The four-dimensional progressive barcode is a printed mark that does not change in size as it is used to represent different stages (or “states”) in a workflow. The addition of progressive information to a barcode allows it to change through time—supporting many different information lifecycles.1,2 This means that the use of the same barcode location for multiple barcodes through time is possible. Progressive barcodes can be also used to support two (or more) applications or services in the same object. One of these can be standards compliant and another can be proprietary or customized. Thus, a “hybrid” of two functions, represented by two planes of information, is combined in a single mark.
These two planes of information include different densities of information. The first plane is binary, with high contrast between the two binary encoding (usually black and white) tiles in the barcode. The second is n-ary, and utilizes inks that are invisible to the binary barcode reading software. This is accomplished with highly saturated colors, but it can also be used with IR, UV or other “invisible” inks.
In this article, the authors will demonstrate several types of applications and services that are enabled by the progressive barcode. They are most effectively deployed when there are multiple types of information payloads needed for a single object—e.g., point-of-sale and customer interrogation of the product. This also makes them useful in a variety of document/physical item workflows.
A novel transfer technique using AC high fields, which are composed of high AC components having peak electric fields around the discharge limit and lower DC components than those used in conventional printers, has been developed, and the functions of each component on toner transfer have been studied by observations of the toner behavior and the discharge. From the observations of the toner behavior, it has been revealed that the high AC components generate reciprocating motions of toner particles in recessed portions of papers, and reduce the toner adhesion by repeatedly providing mechanical and electrical interactions among toner particles. Furthermore, from the observations of the discharge, it is indicated that by using the low DC components, toner particles, whose adhesions are reduced by the high AC components, are transferred onto paper without discharge generation. Due to the functions of the AC and DC field components, uniform images can be realized even on heavily textured papers which have over 100 μm height difference between the highest and lowest points of the surface.
Inkjet ink colorants usually require different substrate modification depending on the colorant chemistry, solvent composition, and ink formulation. In this work, the authors investigated a novel concept based on alternating layers of anionic and cationic polyelectrolytes on a paper surface and the impact on ink colorant fixing and liquid absorption. The effect of nanoparticles in polyelectrolyte layers was investigated in order to clarify the changes in absorption rates. The alternating layering of micron-thin layers of cationic and anionic polyelectrolytes subjected to interim drying showed that the spreading and absorption of nanosize pigmented water-based ink were sensitive to the charge characteristics of the polyelectrolyte multilayer and also to the presence of nanopigments that enhanced the absorption speed and capacity. The interlayer polyelectrolyte complexing resulted not only in different ink-trapping fixing effects, but also in varying uniformity in ink spreading and absorption.