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- ItemElectroless-deposited platinum antennas for wireless surface acousticwave sensors(Basel : MDPI AG, 2019) Brachmann, E.; Seifert, M.; Neumann, N.; Alshwawreh, N.; Uhlemann, M.; Menzel, S.B.; Acker, J.; Herold, S.; Hoffmann, V.; Gemming, T.In an effort to develop a cost-efficient technology for wireless high-temperature surface acoustic wave sensors, this study presents an evaluation of a combined method that integrates physical vapor deposition with electroless deposition for the fabrication of platinum-based planar antennas. The proposed manufacturing process becomes attractive for narrow, thick, and sparse metallizations for antennas in the MHz to GHz frequency range. In detail, narrow platinum-based lines of a width down to 40 μm were electroless-deposited on γ -Al2O3 substrates using different seed layers. At first, the electrolyte chemistry was optimized to obtain the highest deposition rate. Films with various thickness were prepared and the electrical resistivity, microstructure, and chemical composition in the as-prepared state and after annealing at temperatures up to 1100 °C were evaluated. Using these material parameters, the antenna was simulated with an electromagnetic full-wave simulation tool and then fabricated. The electrical parameters, including the S-parameters of the antenna, were measured. The agreement between the simulated and the realized antenna is then discussed.
- ItemPoisoning of bubble propelled catalytic micromotors: The chemical environment matters(Cambridge [u.a.] : Royal Society of Chemistry, 2013) Zhao, G.; Sanchez, S.; Schmidt, O.G.; Pumera, M.Self-propelled catalytic microjets have attracted considerable attention in recent years and these devices have exhibited the ability to move in complex media. The mechanism of propulsion is via the Pt catalysed decomposition of H2O2 and it is understood that the Pt surface is highly susceptible to poisoning by sulphur-containing molecules. Here, we show that important extracellular thiols as well as basic organic molecules can significantly hamper the motion of catalytic microjet engines. This is due to two different mechanisms: (i) molecules such as dimethyl sulfoxide can quench the hydroxyl radicals produced at Pt surfaces and reduce the amount of oxygen gas generated and (ii) molecules containing -SH, -SSR, and -SCH3 moieties can poison the catalytically active platinum surface, inhibiting the motion of the jet engines. It is essential that the presence of such molecules in the environment be taken into consideration for future design and operation of catalytic microjet engines. We show this effect on catalytic micromotors prepared by both rolled-up and electrodeposition approaches, demonstrating that such poisoning is universal for Pt catalyzed micromotors. We believe that our findings will contribute significantly to this field to develop alternative systems or catalysts for self-propulsion when practical applications in the real environment are considered.
- ItemEffect of surfactants on the performance of tubular and spherical micromotors-a comparative study(Cambridge : Royal Society of Chemistry, 2014) Simmchen, Juliane; Magdanz, Veronika; Sanchez, Samuel; Chokmaviroj, Sarocha; Ruiz-Molina, Daniel; Baeza, Alejandro; Schmidt, Oliver G.The development of artificial micromotors is one of the greatest challenges of modern nanotechnology. Even though many kinds of motors have been published in recent times, systematic studies on the influence of components of the fuel solution are widely missing. Therefore, the autonomous movement of Pt-microtubes and Pt-covered silica particles is comparatively observed in the presence and absence of surfactants in the medium. One representative of each of the three main surfactant classes – anionic (sodium dodecyl sulfate, SDS), cationic (benzalkonium chloride, BACl) and non-ionic (Triton X) – has been chosen and studied.