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Simultaneous stimulation and recording of retinal nerve cells with penetrating three dimensional multi-electrode arrays (MEA) on a localized area is a demanding challenge in next generation retina implant research. Within the scope of this research we developed a device to stimulate a network of bi-polar cells and record retinal ganglion cells with a slight time gap to overcome long recording dead times and switching artifacts in common stimulation-and recording systems. The device contains a four channel stimulator capable of pushing arbitrary bi-polar charges into the tissue and a 16 channel commercial electrophysiology interface chip. The device is a miniaturized front-end for our former developed embedded wireless communicating sensor node. First tests in in-vitro retina slices on adult rat with our device show reliable recordings of ganglia cell activity below 1ms after the bi-polar cell stimulation. Index Terms-functional electrical stimulation, neuronal recording, retina implant, embedded system

To understand the neural processes within retina cell layers recent retina implant research focusses on bidirectional communication with bi-polar and ganglion cells in in-vitro retinal tissue. In order to enable this research we had developed a front-end to stimulate and record retinal cell layers with a slight time gap only and thus avoiding long recording dead times. To ease experiments with this front-end, we developed a versatile and user optimized embedded data acquisition device, named iNODE5. This can be configured using a LabVIEW based graphical user interface. We adapted the front-end to the form factor of the commercial measurement device USB-6009OEM from National Instruments. Now, for evaluation and parameter testing the front-end can be plugged into the National Instruments board and controlled via a graphical user interface which enables the export of the basic configuration parameters for later automated standalone measurement and stimulation. For this the front-end is attached to the iNODE5 which reads the experiment configuration from the personal computer via USB or SD-card. The automated electrical stimulation and recording can be started or stopped by a terminal program or a button placed on the iNODE5.

Mitglied derHelmholtz-Gemeinschaft For the development of robust methods to significantly reduce friction drag caused by the turbulent boundary layer the DFG research group FOR1779 analyses the effect of transversal waves on an extended aluminum surface in wind tunnel experiments. The transversal surface waves running in the span direction (orange arrow) cause an interaction with the near-surface flow field (blue arrow).An actuation system developed by ZEA-2 generating the transversal waves by phase-shifted driven, parallel orientated and uniformly distributed electromagnetic actuators. These actuators are glued to the aluminum surface and hence are mechanically coupled. Sketch of the electromagnetic actuator system.For the generation of the running transversal waves, the actuators are driven by the FPGA RIO board PXI-7831 R from National Instruments via an analogue amplifier front-end. The Virtex-II FPGA Chip included in this board provides automated calculated smooth signal transition when adapting the signal characteristics on the external change of the wave parameters amplitude, frequency and wavelength. This prevents discontinuous signals slope with high frequency interference on the aluminum surface. The high frequency interference by rapid parameter changes without smooth signal transition is shown on the left versus a parameter change with calculated smooth signal transitions on the right.We implemented the smooth wavelength transition based on direct digital synthesis (DDS). This method ensures a smooth wavelength transition by means of an intelligent manipulation of the readout steps of a stored waveform look-up Smooth Wavelength Transition MethodAs mentioned in the previous chapter, the look-up table is sampled with different step sizes as a function of the wave frequency. Each amplitude value of the signal has its own sample in the memory which is known as the memory point P 0 combining an amplitude value to the sample at S 0 ,Phase shift of 60°by moving the zero crossing point at 2π to the point S3.The method of changing the phase, without high-frequency interferences caused by rapid changes in the voltage and its effects on the aluminum surface, is a negative or positive time shift of the signal by moving the zero crossing point by increasing or decreasing the readout steps while the memory controller is at the sample of the amplitude value P n of the changing phase.This assumption could be made by the characteristic of a periodic and zerocentered signal that the phase value always appears positive or negative every quartered period. By the time the calculated phase value reaches the memory point S 0 , the zero crossing following after a half-period is shifted to the sample position of S 3 . This results in a faster sampling CS New of the memory so that the zero crossing is reached earlier.The developed electromagnetic actuator system is used for experiments to develop robust methods for turbulent friction resistance reduction by transversal surface waves. In case of changing inflow conditions wav...

Abstract-This work discusses the use of analog light barrier and Hall sensors for waveform control in an actuator system for turbulence research. The system shall produce up to 80 Hz, 80 mm wavelength running surface wave with amplitudes from 50 to 1000 µm. To ensure both, waveform and amplitude, the control algorithm requires real time amplitude measurements of all 20 actuators. Techniques are described to extend the limited measurement range of analog light barriers and to reduce impact of mechanical disturbances on the measurement process by placement and compensation. Also a small bar permanent magnet together with Hall sensors to track position are employed and a method for reducing impact of the strong magnetic stray fields affecting Hall sensors in this actuator system is developed.