Abstract A conductive inkjettable fluid was formulated based on carbon-coated copper nanoparticles. The copper particles were produced by vapor-phase reduction of copper chloride and coated in situ with carbon. The average particle size was 44‐88 nm depending on the chosen production parameters. The optimized fluid was a water/ethylene glycol monobutyl ether/n-propanol mixture with 25 wt% nanoparticles, stabilized by a polymeric dispersing agent. A conductivity of 6.4 S/m was obtained with a single deposited layer without sintering or high-temperature annealing. The materials are interesting for several applications such as antistatic coatings, resistors, and sensors.

Abstract A method for spatially selective etching of dielectric layers using an aerosol jet printer is described. The method, referred to as direct etching, was first implemented using inkjet printing. This article reports on the adaption of the method to operate on an ‘Optomec’ aerosol jet printer in order to increase patterning resolution and processing throughput, as required for commercial photovoltaic applications. It is demonstrated that the etching process can be tailored to different applications by varying the processing parameters, such as the gas flow rates, platen movement speed and number of printing passes. The results presented in this article show that grooves as narrow as 20 μm can be etched in dielectric layers that are commonly used for passivation of commercially produced silicon solar cells. Accurate alignment enabled by the ‘Optomec’ aerosol jet printer allowed etched patterns to be formed in pre-patterned surfaces, a property that may find application in a number of selective-emitter solar cell designs which currently use aligned screen printing for metallization. In addition, a method of etching point openings for metal contacts for enhanced rear surface passivation is presented and discussed.

Abstract Although significant progress has been made toward digital printing of electronics using inkjet technologies, the potential of laser printing for digital fabrication has been largely overlooked. Despite their speed and resolution capabilities toner-based systems are often regarded as incapable of handling conductive materials. This research reports recent laser printing development and its potential to replace conventional printed circuit board manufacturing steps, including conductive track deposition. The research had a dual focus, demonstrating proof of concept with conventional office laser printers (for artwork masks, etch resists, and seed layers for overplating), and used industrial laser printers with developmental toners to support direct production of electronics (conductive tracks, dielectric layers, and legends). The results confirm that laser printing can complement other digital printing approaches for directly depositing resists and conductive tracks.

Abstract Large-scale production of organic photovoltaics (OPVs) at low cost is, still, a future concept thought to promote the market share of solar energy. Working towards the roll-to-roll production of OPVs, different compatible deposition techniques are investigated. Inkjet printing is a promising candidate, as it allows the contact-free deposition of patterned functional materials with high flexibility. In this article, we further extend the application of inkjet printing for roll-to-roll production of OPVs. Inkjet-printed high-conducting PEDOT:PSS is compatible with indium tin oxide-free devices, by combination with an Ag grid to form the anode. A P3HT/PCBM layer is inkjet printed on top using non-chlorinated halogen-free solvents only, and large-area homogeneous layers with surface areas up to 3 cm by 3 cm were obtained. The device thus manufactured showed performance comparable to a reference device with spin-coated layers for which chlorobenzene was used as solvent for the photoactive layer. This is an essential step forward in the knowledge on materials and process conditions using inkjet printing for OPVs and working towards the full roll-to-roll production of OPVs without loss of performance.

Abstract A method for isolating interdigitated metal contacts for rear contact solar cells using aerosol-printed polymer masking lines which can “lift off” overlying metal during a sonication step is described. Aluminum lift-off is demonstrated with masking lines formed by aerosol-printed novolac resin and polyacrylic acid. By printing novolac resin lines that are ∼10 μm high, lift-off of evaporated aluminum in an ultrasonic bath reliably resulted in 100 to 170 μm isolation gaps being formed between n-type and p-type rear contacts on different wafer surfaces. Performing this lift-off process using water-soluble polyacrylic acid lines may be advantageous due to the less expensive recovery of lift-off metal from the sonication bath.

Abstract The current engineered skin substitutes for diabetic foot ulcer treatment lack effective host integration. The goal of this research is to create a wound care material that promotes integration with host tissue. We have been investigating a printable biodegradable scaffold composed of gelatin and oxidized alginate, both materials with very high biocompatibility and low toxicity. We investigated the printability of oxidized alginate and its use as an ‘ink’ for drop-on-demand crosslinking of gelatin. The oxidized alginate was characterized by Fourier transform infrared spectrophotometry. Crosslinking rates were investigated as a function of crosslinker concentration. Crosslinking densities were measured by trinitrobenzene sulfonic acid assay. The mechanical properties of the crosslinked gels were measured in dried samples. The biocompatibility and ability of the printed scaffolds to support fibroblast attachment and proliferation were tested. Our results show that using 15% oxidized alginate and 10% gelatin allows us to obtain skin wound dressings with better properties.

Abstract There are a number of plate imaging options for flexographic printing. The type of plate used and the way it is processed affect the trace resolution and ink transfer of the conductive material. The authors have recently completed one of, if not the largest research studies ever conducted in printed electronics. Over 45,000 resistances were measured and nearly 1000 three-dimensional optical profiles were obtained, from which a variety of morphological parameters were measured. Many printing variables were examined, including plate material, imaging and plate processing conditions, trace orientation, anilox cell volume, plate type, line and gap width, and orientation. Aqueous, nano-silver inks were printed on both PET and coated paper. The impact of these printing process variables on the conductivity and resulting printed trace width and minimum reverse will be discussed.