Cultured neurons on multi electrode arrays (MEAs) have been widely used to study various aspects of neuronal (network) functioning. A possible drawback of this approach is the lack of structure in these networks. At the single cell level, several solutions have been proposed to enable directed connectivity, and promising results were obtained. At the level of connected sub-populations, a few attempts have been made with promising results. First assessment of the designs' functionality, however, suggested room for further improvement. We designed a two chamber MEA aiming to create a unidirectional connection between the networks in both chambers (“emitting” and “receiving”). To achieve this unidirectionality, all interconnecting channels contained barbs that hindered axon growth in the opposite direction (from receiving to emitting chamber). Visual inspection showed that axons predominantly grew through the channels in the promoted direction. This observation was confirmed by spontaneous activity recordings. Cross-correlation between the signals from two electrodes inside the channels suggested signal propagation at ≈2 m/s from emitting to receiving chamber. Cross-correlation between the firing patterns in both chambers indicated that most correlated activity was initiated in the emitting chamber, which was also reflected by a significantly lower fraction of partial bursts (i.e., a one-chamber-only burst) in the emitting chamber. Finally, electrical stimulation in the emitting chamber induced a fast response in that chamber, and a slower response in the receiving chamber. Stimulation in the receiving chamber evoked a fast response in that chamber, but no response in the emitting chamber. These results confirm the predominantly unidirectional nature of the connecting channels from emitting to receiving chamber.

Blends of self-assembling polystyrene-block-poly(4vinyl pyridine) (PS-b-P4VP) diblock-copolymers and poly(4vinyl pyridine) (P4VP) homopolymers were used to fabricate isoporous and nanoporous films. Block copolymers (BCP) selfassembled into a structure where the minority component forms very uniform cylinders, while homopolymers, resided in the core of the cylinders. Selective removal of the homopolymers by ethanol immersion led to the formation of wellordered pores. In films without added homopolymer, just immersion in ethanol and subsequent swelling of the P4VP blocks was found to be sufficient to create pores. Pore sizes were tuned between 10 and 50 nm by simply varying the homopolymer content and the molecular weight of the blockcopolymer. Uniformity was lost when the average pore size exceeded 30 nm because of macrophase separation. However, preparation of films from low M W diblock copolymers showed that it is possible to have excellent pore size control and a high porosity, while retaining a low pore size distribution. V C 2014

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Low-pressure chemical vapour deposited (LPCVD) in situ phosphorus-Dodd polysilicon films have been grown from a 60:30:300 seem silane:phosphine (2000 ppm):nitrogen mass-flow mixture at 625 "C under varied process conditions. Thickness uniformity, grain size, dopant concentration, resistivity, temperature coefficient of resistivity, longitudinal strain gauge factor and the temperature coefficient of the gauge factor are determined. A growth rate with a non-uniformity (30) of 5% is obtained, yielding films with a grain size of 20-30 nm and a surface roughness of 12 nm (peak-to-valley heights), both before and after annealing, and a dopant concentration of (2-3) x lpcrn3.Resistivities of the order of 1 II-&~ cm can be obtained with a temperature coefficient close to zero after annealing at 900 "C for 30 min, with a longitudinal gauge factor of -20 and a temperature coefficient of the gauge factor of -0.25%/"C. A mechanism incorporating the diffusion of dislocations during annealing is proposed to explain the observed effect. The films are appropriate for application as resistors for thermal excitation and piezoresistive detection in resonating micromechanical devices, Resonating micromechanical structures consist of an element for the excitation and an element for the detection of the vibration of the structure. These elements can be an integral part of the structure, see Fig. 1, with an excitation element for .exerting a bending moment, and a detection element to detect bending strain. One technique makes use of resistive heating for thermal excitation and resistive strain gauges for detection. For our resonating membrane mass-flow sensor [ 191 as well as for our resonating microbridge mass-flow sensor [20], we make use of in situ phosphorus doping of low-pressure chemical vapour deposited (LPCVD) polysilicon for the excitation and the detection resistors, together with a single-crystal silicon substrate. We will first discuss the advantages of polysilicon for this application, and then we will give reasons for our choice of in situ doping with phosphorus.