Search

Improving the interface between electrodes and neurons has been the focus of research for the last decade. Neuroelectrodes should show small geometrical surface area and low impedance for measuring and high charge injection capacities for stimulation. Increasing the electrochemically active surface area by using nanoporous electrode material or by integrating nanostructures onto planar electrodes is a common approach to improve this interface. In this paper a simulation approach for neuro electrodes' characteristics with integrated high aspect ratio nano structures based on a point-contact-model is presented. The results are compared with experimental findings conducted with real nanostructured microelectrodes. In particular, effects of carbon nanotubes and gold nanowires integrated onto microelectrodes are described. Simulated and measured impedance properties are presented and its effects onto the transfer function between the neural membrane potential and the amplifier output signal are studied based on the point-contact-model. Simulations show, in good agreement with experimental results, that electrode impedances can be dramatically reduced by the integration of high aspect ratio nanostructures such as gold nanowires and carbon nanotubes. This lowers thermal noise and improves the signal-to-noise ratio for measuring electrodes. It also may increase the adhesion of cells to the substrate and thus increase measurable signal amplitudes. [ABSTRACT FROM AUTHOR]

Planar lipid bilayers constitute a versatile method for measuring the activity of protein channels and pores on a single molecule level. Ongoing efforts attempt to tailor this method for detecting biomedically relevant target analytes or for high-throughput screening of drugs. To improve the mechanical stability of bilayer recordings, we use a thin-film epoxy resist ADEX as septum in free-standing vertical bilayers. Defined apertures with diameters between 30 µm and 100 µm were micro-fabricated by photolithography. The performance of these septa was tested by functional reconstitution of the K+ channel KcvNTS in lipid bilayers spanned over apertures in ADEX or Teflon films; the latter is conventionally used in bilayer recordings and serves as reference. We observe that the functional properties of the K+ channel are identical in both materials while ADEX provides no advantage in terms of capacitance and signal-to-noise ratio. In contrast to Teflon, however, ADEX enables long-term experimental recordings while the stability of the lipid bilayer is not compromised by pipetting solutions in and out of the recording chamber. Combined with the fact that the ADEX films can be cleaned with acetone, our results suggest that ADEX carries great potential for multiplexing bilayer chambers in robust and reusable sensing devices. [ABSTRACT FROM AUTHOR]

Conical metallic nanostructures, due to their geometrical and physical properties, are advantageous compared to cylindrical nanowires in applications like electron field emission cathodes. In this paper a new method for fabrication and integration of vertically aligned metallic nanocones with random distribution is reported. The nanocones are deposited electrochemically at temperatures about 60 °C and lower. An area of ca. 1 cm 2 is covered with nanocones. The density of nanocones ranges between 6 × 10 4 and 2 × 10 6 cm − 2 , which gives a pitch range of 23 to 7 μm. With this process the growth and integration of nanocones made of different materials like e.g. Au, Ni and Cu are enabled. The tip diameter of the cones can be modified between 50 and 700 nm and the base diameter between 2.5 and 7 μm, i.e. apex angles between 5.9° and 16.6° can be obtained. The surface roughness of the nanocone arrays is ± 0.2 μm. [ABSTRACT FROM AUTHOR]

Soft silicone elastomers are used in a generation of dielectric elastomer actuators (DEAs) with improved actuation speed and durability compared to the commonly used, highly viscoelastic polyacrylate 3M VHB™ films. The maximum voltage-induced stretch of DEAs is ultimately limited by their dielectric breakdown field strength. We measure the dependence of dielectric breakdown field strength on thickness and stretch for a silicone elastomer, when voltage-induced deformation is prevented. The experimental results are combined with an analytic model of equi-biaxial actuation to show that accounting for variable dielectric field strength results in different values of optimal pre-stretch and thickness that maximize the DEA actuation. [ABSTRACT FROM AUTHOR]

The permanent magnetic linear contactless displacement (PLCD) sensor is a new type of displacement sensor operating on the magnetic inductive principle. It has many excellent properties and has already been used for many applications. In this article a Micro-PLCD sensor which can be used for microelectromechanical system (MEMS) measurements is designed and simulated with the CST EM STUDIO® software, including building a virtual model, magnetostatic calculations, low frequency calculations, steady current calculations and thermal calculations. The influence of some important parameters such as air gap dimension, working frequency, coil current and eddy currents etc. is studied in depth. [ABSTRACT FROM AUTHOR]

The permanent magnetic linear contactless displacement (PLCD) sensor is a new type of displacement sensor operating on the magnetic inductive principle. It has many excellent properties and has already been used for many applications. In this article a Micro-PLCD sensor which can be used for microelectromechanical system (MEMS) measurements is designed and simulated with the CST EM STUDIO® software, including building a virtual model, magnetostatic calculations, low frequency calculations, steady current calculations and thermal calculations. The influence of some important parameters such as air gap dimension, working frequency, coil current and eddy currents etc. is studied in depth. [ABSTRACT FROM AUTHOR]

The new acrylic photoresist named AZ 125 nXT is a serious option for low-cost high-aspect-ratio UV LIGA applications. It offers advantages compared to SU-8 like good adhesion to Si substrates, rapid processing, and easy removal after electroplating. Film thicknesses of 400, 800, and 1400 \mu \m with an aspect ratio of 20 : 1 have been shown by the authors. The photoresist's excellent electroforming behavior has been proved in an extremely acid copper electrolyte at room temperature as well as in an almost neutral nickel electrolyte at 50 ^\circ \C. The easy removal (wet: dimethyl sulfoxide or acetone, dry: plasma with reactive radicals) releases freestanding metal structures with aspect ratios of 13 : 1 and 16 : 1. \hfill[2010-0307] [ABSTRACT FROM PUBLISHER]