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- ItemSoft Inkjet Circuits: Rapid Multi-Material Fabrication of Soft Circuits using a Commodity Inkjet Printer(New York City : Association for Computing Machinery, 2019) Khan, Arshad; Roo, Joan Sol; Kraus, Tobias; Steimle, JürgenDespite the increasing popularity of soft interactive devices, their fabrication remains complex and time consuming. We contribute a process for rapid do-it-yourself fabrication of soft circuits using a conventional desktop inkjet printer. It supports inkjet printing of circuits that are stretchable, ultrathin, high resolution, and integrated with a wide variety of materials used for prototyping. We introduce multi-ink functional printing on a desktop printer for realizing multi-material devices, including conductive and isolating inks. We further present DIY techniques to enhance compatibility between inks and substrates and the circuits' elasticity. This enables circuits on a wide set of materials including temporary tattoo paper, textiles, and thermoplastic. Four application cases demonstrate versatile uses for realizing stretchable devices, e-textiles, body-based and re-shapeable interfaces.
- ItemUltrathin gold nanowires for transparent electronics: breaking barriers(Amsterdam : Elsevier, 2016) Gonzalez-Garcia, Lola; Maurer, Johannes H.M.; Reiser, Beate; Kanelidis, Ioannis; Kraus, TobiasNovel types of Transparent Conductive Materials (TCMs) based on metal nanostructures are discussed. Dispersed metal nanoparticles can be deposited from liquids with moderate thermal budgets to form conductive films that are suitable for thin-film solar cells, displays, touch screens, and nanoelectronics. We aim at new TCMs that combine high electrical conductivity with optical transparency and mechanical flexibility. Wet-processed films of randomly arranged metallic nanowires networks are commercially established and provide a relatively cost-effective, scalable production. Ultrathin gold nanowires (AuNWs) with diameters below 2 nm and high aspect ratios have recently become available. They combine mechanical flexibility, high optical transparency, and chemical inertness. AuNWs carry oleylamine capping ligands from synthesis that cause high contact resistances at their junctions. We investigated different annealing processes based on temperature and plasma treatment, to remove the ligands after deposition and to allow electrical conductivity. Their effect on the resulting nanostructure and on the material properties was studied. Scanning Electron Microscopy (SEM) and optical spectroscopy revealed changes in the microstructure for the different post-treatments. We found that the conductivity and the stability of the TCM depended strongly on its final microstructure. We demonstrate that the best results are obtained using H2-plasma treatment.
- ItemMathematical model for a heat pump dryer for aromatic plant(Amsterdam : Elsevier, 2013) Hossain, Mohammed Ayub; Gottschalk, Klaus; Hassan, Mohammad ShoebA mathematical model was developed to evaluate the performance of heat pump dryer for drying of aromatic plants. The model consists of three sub-models; namely, drying model, heat pump model, and performance model. Drying model was developed based on mass balance, heat balance, heat transfer and drying rate equations. Heat pump sub-model consists of some theoretical and empirical equations for estimating the parameters of evaporator, compressor, condenser and expansion valve. The performance sub-model was the equations for prediction of drying efficiency, COP (coefficient of performance), MER (moisture evaporating rate) and SMER (specific moisture evaporating rate). The model was validated with the experimental data. The experiments was conducted in a fixed bed drying of valerian roots (Valeriana officinalis L.) in cooperation with a agricultural company (Agrargenossenschaft Nöbdenitz e.G., Thüringen) in Thüringen, Germany. Data logger was used to record the temperature, relative humidity, humidity ratio and enthalpy of air at different positions of the dryer equipped with different types of sensors. The average drying air temperature was 36.84°C and relative humidity was about 20%. About 89 hours were required to reduce the moisture content of valerian roots from 89 to 9% (wb). The simulated results (temperature, relative humidity and moisture content) agreed well with the experimental results. The average COP, MER and SMER and drying efficiency were 5.45, 140.03 kg/h, 0.038 kg/kWh, and 78.23%, respectively. This model may be used for design data for heat pump dryer for drying of aromatic plants as well as other heat sensitive crops.
- ItemTransparent conductive oxides for coating applications(Saarbrücke : Leibniz-Institut für Neue Materialien, 2009) Quilitz, Mario; Oliveira, Peter W. de; Heusing, Sabine; Veith, MichaelTransparent, conductive oxides (TCOs) applied as coatings find multiple applications in various areas such as flat panel display setups, as electrodes in touch-screen panels, electrochromic devices, solar cells and in architectural applications for example as IR reflectors. The favored material in the class of TCOs is still ITO - Sn-doped In2O3 - due to its unique combination of high transparency and electrical conductivity. Though already very good, the potential of the ITO coatings with regard to their conductivity leaves some space for future improvements. Also ITO as a material has some serious drawbacks, such as limited availability and high costs. this work presents some stratgies to overcome these obstacles. One way to enhance the conductivities of alternative materials is to use carbon nanotubes as a dopant. This strategy was tested for ATO (Antimony-doped Tin Oxide), Titan dioxide and AZO (Aluminium-doped Zinc oxide). The results for these materials are presented. In coatings of ITO on glass or polymeric foils usually silica-based binders are used. They have the disadvantage to reduce the contact between the highly conducting grains and thus reduce overall conductivity in the composite. The matrix between the nanoparticles can be improved by several measures. Experiments with relevance in this direction are discussed. A third strategy aims at the reduction of costs in the process of ITO fabrication. Here one way to go is to use an electrochemical synthesis method. Results of the line of development are presented. Other strategies comprise the suitable processing of materials with a lower intrinsic conductivity or the search for materials with high intrinsic conductivity close to that of ITO. Exmples are presented and discussed.
- ItemLarge area production of optical coatings and devices by the sol-gel process(Saarbrücke : Leibniz-Institut für Neue Materialien, 2009) Oliveira, Peter; Quilitz, Mario; Heusing, Sabine; Lin, Hechun; Veith, Michael[no abstract available]