We have studied the formation of ohmic contacts to InAs nanowires by chemical etching and passivation of the contact areas in an ammonium polysulfide, (NH4)2Sx, water solution. The nanowires were exposed to different dilution levels of the (NH4)2Sx solution before contact metal evaporation. A process based on a highly diluted (NH4)2Sx solution was found to be self-terminating, with minimal etching of the InAs. The stability of the contacts was investigated with electrical measurements as a function of storage time in vacuum and air.

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We used epitaxially grown monodisperse nanowire arrays to measure cellular forces with a spatial resolution of 1 mum. Nerve cells were cultured on the array and cellular forces were calculated from the displacement of the nanowire tips. The measurements were done in situ on live cells using confocal microscopy. Forces down to 15 pN were measured on neural growth cones, showing that this method can be used to study the fine details of growth-cone dynamics.

We present an electrode, based on structurally controlled nanowires, as a first step towards developing a useful nanostructured device for neurophysiological measurements in vivo. The sensing part of the electrode is made of a metal film deposited on top of an array of epitaxially grown gallium phosphide nanowires. We achieved the first functional testing of the nanowire-based electrode by performing acute in vivo recordings in the rat cerebral cortex and withstanding multiple brain implantations. Due to the controllable geometry of the nanowires, this type of electrode can be used as a model system for further analysis of the functional properties of nanostructured neuronal interfaces in vivo.

Two‐in‐one: A biological supercapacitor—a combination of an electrochemical capacitor and an enzymatic fuel cell—is presented. Both the capacitor and the biofuel cell are built from nanomaterials, namely, polyaniline/carbon nanotube composites and redox enzyme/gold nanoparticle assemblies. The biosupercapacitor is self‐charging, membrane‐ and mediator‐less.

Nanoscale contacts between metals and semiconductors are critical for further downscaling of electronic and optoelectronic devices. However, realizing nanocontacts poses significant challenges since conventional approaches to achieve ohmic contacts through Schottky barrier suppression are often inadequate. Here we report the realization and characterization of low n-type Schottky barriers (B0.35 eV) formed at epitaxial contacts between Au-In alloy catalytic particles and GaAs-nanowires. In comparison to previous studies, our detailed characterization, employing selective electrical contacts defined by high-precision electron beam lithography, reveals the barrier to occur directly and solely at the abrupt interface between the catalyst and nanowire. We attribute this lowest-to-date-reported Schottky barrier to a reduced density of pinning states (B10 17 m À 2 ) and the formation of an electric dipole layer at the epitaxial contacts. The insight into the physical mechanisms behind the observed lowenergy Schottky barrier may guide future efforts to engineer abrupt nanoscale electrical contacts with tailored electrical properties.

Miniature, self-contained biodevices powered by biofuel cells may enable a new generation of implantable, wireless, minimally invasive neural interfaces for neurophysiological in vivo studies and for clinical applications. Here we report on the fabrication of a direct electron transfer based glucose/oxygen enzymatic fuel cell (EFC) from genuinely three-dimensional (3D) nanostructured microscale gold electrodes, modified with suitable biocatalysts. We show that the process underlying the simple fabrication method of 3D nanostructured electrodes is based on an electrochemically driven transformation of physically deposited gold nanoparticles. We experimentally demonstrate that mediator-, cofactor-, and membrane-less EFCs do operate in cerebrospinal fluid and in the brain of a rat, producing amounts of electrical power sufficient to drive a self-contained biodevice, viz. 7 mW cm 22 in vitro and 2 mW cm 22 in vivo at an operating voltage of 0.4 V. Last but not least, we also demonstrate an inductive coupling between 3D nanobioelectrodes and living neurons. R esearch on neural interfaces has the potential to revolutionise our understanding of fundamental neural mechanisms and is likely to engender new opportunities for clinical diagnosis and therapy [1][2][3] . Microscale autonomous, i.e. self-powered and wirelessly communicating, biodevices constitute a new generation of implantable neural interfaces. Such biodevices enable minimally intrusive, in vivo neurophysiological studies and therapies on a sub-cellular level. The overall dimensions and self-sufficiency of the biodevices significantly improve the implantable properties, thus enabling an unprecedented level of biodevice biocompatibility, reliability, and longevity due to complete physical and electrical decoupling from external devices. Indeed, such selfcontained biodevices may reveal the full potential of nanostructure based neuronal interfaces for in vivo applications 4,5 . Wireless self-powered neural biodevices could for instance carry a probe for neuronal signal detection connected to a nano-amplifier and a nano-transmitter; all of which could be powered by a membrane-and mediatorless enzymatic fuel cell (EFC, Fig. 1). The functionality of these discrete nanoelectronic elements has already been demonstrated [6][7][8] . Moreover, in vivo studies of nanowire based neuronal electrodes have recently been performed 9 . Our work details the last element needed to design autonomous microscale biodevices, viz. an electric power source, specifically, a non-toxic and miniature EFC, capable of in vivo operation.EFCs belong to a broad family of biofuel cells, which directly convert chemical energy into electric energy using biological catalysts, e.g. redox enzymes or even whole living cells 10,11 . Glucose/oxygen EFCs should provide a reliable source of electric energy for brain-device interfaces utilising the readily available biofuel, e.g. glucose, and biooxidant, e.g. molecular oxygen (O 2 ), tapping into the same energy source as the biological entities of the br...

We present an EBL-defined nanowire pattern that can sort axons coming from different directions on a substrate. The pattern defines tracks for left-bound traffic and right-bound traffic, which opens up new possibilities for designing neural networks on a chip.