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Item type:Publication, Access status: with files , Bioimpedance analysis of L929 and HaCaT cells in low frequency range(De Gruyter, 2018-09-01); ; ; In this work, Bioimpedance Spectroscopy (BIS) is used to study fuids and cell solutions. A new four-electrode-terminal (4T) chamber using 3D printing and stainless steel corrosion resistant V4A was designed to measure the impedance of live cell solutions at the frequency range 0.1Hz-1MHz. At f < 1kHz the double layer (DL) that builds at electrode's surface raises the impedance substantially preventing the observation of the real impedance of the cells. The new 4T design circumvents the DL, is more robust and cheap, and allows for the repeatability of the results. Experiments were performed in vitro with two cell lines, L929 (mouse fbroblasts) and HaCaT (human keratinocytes). Results show that it is possible to distinguish between the two cell types by means of its BIS measurements in the new setup. Also, a low-frequency dispersion (α-dispersion) was observed in HaCaT cells solution, but not in L929. Furthermore, a potentiostat circuit model was developed in LTSpice to simulate the hardware setup and two different circuit models were used to ft cell's data. © 2018 Viviane S. Teixeira et al.Publicationtype: Journal ArticleScopus© Citations 6 298 434 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Integrated circuit with memristor emulator array and neuron circuits for biologically inspired neuromorphic pattern recognition(World Scientific Publishing (WSPC), 2017-04-27); ; ; ; This paper details an application-specific integrated circuit (ASIC) with an array of switched-resistor-based memristors (resistor with memory) and integrate & fire (I & F) neuron circuits for the development of memristor-based pattern recognition. Since real memristors are not commercially available, a compact memristor emulator is needed for device study. The designed ASIC has five memristor emulators with one having a conductance range from 4.88ns to 4.99μs (200kOhm) to 204.8MOhm)) and other four having conductance ranging from 195ns to 190μs (5.2kOhm) to 5.12MOhm)). Signal processing has been planned to be off-chip to get the freedom of programmability of a wide range of memristive behavior. This paper introduces the memristor emulator and the realization of synapse functionalities used in neuromorphic circuits such as long term potentiation (LTP), Long Term depression (LTD) and synaptic plasticity. The ASIC has two I & F neuron circuits which are intended to be used in conjunction with memristors in a multiple chip network for pattern recognition. This paper explains the memristor emulator, I & F neuron circuit and a respective neuromorphic system for pattern recognition simulated in LTspice. The ASIC has been fabricated in AMS 350nm process.Publicationtype: Journal ArticleScopus© Citations 11 372 470 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , An enhanced lumped element electrical model of a double barrier memristive device(IOP Publishing, 2017-04-13); ; ; ; The massive parallel approach of neuromorphic circuits leads to effective methods for solving complex problems. It has turned out that resistive switching devices with a continuous resistance range are potential candidates for such applications. These devices are memristive systems - nonlinear resistors with memory. They are fabricated in nanotechnology and hence parameter spread during fabrication may aggravate reproducible analyses. This issue makes simulation models of memristive devices worthwhile. Kinetic Monte-Carlo simulations based on a distributed model of the device can be used to understand the underlying physical and chemical phenomena. However, such simulations are very time-consuming and neither convenient for investigations of whole circuits nor for real-time applications, e.g. emulation purposes. Instead, a concentrated model of the device can be used for both fast simulations and real-time applications, respectively. We introduce an enhanced electrical model of a valence change mechanism (VCM) based double barrier memristive device (DBMD) with a continuous resistance range. This device consists of an ultra-thin memristive layer sandwiched between a tunnel barrier and a Schottky-contact. The introduced model leads to very fast simulations by using usual circuit simulation tools while maintaining physically meaningful parameters. Kinetic Monte-Carlo simulations based on a distributed model and experimental data have been utilized as references to verify the concentrated model.Publicationtype: Journal ArticleScopus© Citations 17 277 364 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , New data recording plugin for the integration of an integrated circuit for neural recordings into the electrophysiology open source user interface Open EphysThe research of various diseases like epilepsy or schizophrenia requires an accurate study of bioelectrical signals. An Application Specific Integrated Circuit (ASIC) for the recording of neural signals from neonatal mice was developed [1]. To integrate the developed ASIC into Open Ephys, an open source electrophysiology user interface, a specific plugin is presented. It enables simple configuration of the ASIC, recording of biomedical signals and enables the utilization of many of Open Ephys’ functions. The user interface is well known to neuroscientific researchers and the presented plugin simplifies the use of the integrated circuit for the researchers dramatically. It also enables the use of the ASIC to other kind of applications like neural recordings from mammalians or recordings for brain computer interfaces.Publicationtype: Conference Paper402 414 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Comparison of single ended and differential signaling for wired biomedical implants using SPI communication with Reed Solomon Error Correction Codes(IEEE, 2017-02); ; ; ; For an implantable system for the recording of brain signals from neonatal mice the design specifications for the weight and the size of a implantable system are very tough. The animals are very small and light weight (1-3 cm, 2-3 g) and the recording data rate is very high (3,5 Mbit/s). Thus, the system has to be extremely small. With state of the art technique it is not possible to set up a wireless implantable system that is suitable for a neonatal mouse. Thus a wired system is developed. For the wired system the connector is a size limiting factor. In wired transmission systems single ended and differential signalling are available. Differential signalling is more robust against noise disturbances, single ended transmission is beneficial with respect to a minimum number of wires and chip area. A detailed comparison of the suitability of both transmission types for wired implantable systems has been performed. A Serial Peripheral Interface connection with Reed Solomon Encoder connection has been implemented. Reed Solomon Error Correction is used to correct the errors occurring on the wired transmission line. Measurements of data rate and error rate for single ended and differential signalling have been performed for long cables (up to 1.8 m). It could be shown that single ended transmission is favourable for the desired application. For the detection and correction of errors occurring on high speed Serial Peripheral Interface Reed Solomon decoding on FPGA was used. This particular decoder design has capability of correcting up to 2 symbol errors on a packet of data composed of 9 symbols where each symbol is 4 bits long. Complete error correction takes about 65 clock cycles on a speed up to 100 MHz.Publicationtype: Conference Paper365 328 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Towards an implantable integrated neural recording system for neonatal mice(Society for Neuroscience, San Diego, CA, 2016-11); ; ; The recording of neural signals from the brain of neonatal mice is of interest for the understanding of the functionality of the brain and its development processes. Treatments for certain forms of neural diseases like epilepsy are investigated with the help of neural recordings from mice [Marguet, Nature Medicine 21, 1436-1444, 2015]. For a systematic investigation of these processes, long term neural recordings of neonatal mice are needed. Neonatal mice have a weight of only 3 - 5 grams; commercially available recording systems are much too heavy and large for this application. To overcome this, an implantable neural recording system is proposed that can be placed inside a neonatal mouse (back, neck and head) and record Low Field Potentials (LFP) and Action Potentials (AP) from the brain.Publicationtype: Journal Article284 233 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , High speed digital interfacing for a neural data acquisition system - Enabling of live display functionality for a neural recording systemDiseases like schizophrenia and genetic epilepsy are supposed to be caused by disorders in the early development of the brain. For the further investigation of these relationships a custom designed application specific integrated circuit (ASIC) was developed that is optimized for the recording from neonatal mice [Bahr A, Abu-Saleh L, Schroeder D, Krautschneider W. 16 Channel Neural Recording Integrated Circuit with SPI Interface and Error Correction Coding. Proc. 9th BIOSTEC 2016. Biodevices: Rome, Italy, 2016; 1: 263; Bahr A, Abu-Saleh L, Schroeder D, Krautschneider W. Development of a neural recording mixed signal integrated circuit for biomedical signal acquisition. Biomed Eng Biomed Tech Abstracts 2015; 60(S1): 298–299; Bahr A, Abu-Saleh L, Schroeder D, Krautschneider WH. 16 Channel Neural Recording Mixed Signal ASIC. CDNLive EMEA 2015 Conference Proceedings, 2015.]. To enable the live display of the neural signals a multichannel neural data acquisition system with live display functionality is presented. It implements a high speed data transmission from the ASIC to a computer with a live display functionality. The system has been successfully implemented and was used in a neural recording of a head-fixed mouse.Publicationtype: Journal ArticleScopus© Citations 1 336 518 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Smart control for functional electrical stimulation with optimal pulse intensity(De Gruyter, 2016-09-30); ; ; ; Transcutaneous electrical stimulation is a common treatment option for patients suffering from spinal cord injury or stroke. Two major difficulties arise when employing electrical stimulation in patients: Accurate stimulation electrode placement and configuration of optimal stimulation parameters. Optimizing the stimulation parameters has the advantage to reduce muscle fatigue after repetitive stimulation. Here we present a newly developed system which is able to automatically find the optimal individual stimulation intensity by varying the pulse length. The effectiveness is measured with flex sensors. By adapting the stimulation parameters, the effect of muscle fatigue can be compensated, allowing for a more stable movement upon stimulation over time.Publicationtype: Journal ArticleScopus© Citations 3 241 387 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , A flexible standalone system with integrated sensor feedback for multi-pad electrode FES of the hand(De Gruyter, 2016-09-30); ; ; ; Functional electrical stimulation aims to help patients suffering from stroke or spinal cord injury to supplement lost motor function. Effective functional electrical stimulation requires precise placement of the stimulation electrode. Finding the correct placement, however, can be difficult and time consuming. Another common problem with functional electrical stimulation is early occurrence of muscle fatigue upon repetitive stimulation, limiting treatment efficiency. Both, precise electrode placement as well as the reduction of muscle fatigue can be achieved using multi-pad electrodes. Here we present a new standalone device for multi-pad functional electrical stimulation. The device is easy to use and designed to help patients recovering from stroke to train and perform opening of the hand.Publicationtype: Journal ArticleScopus© Citations 6 255 343 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Wireless blood pressure measurement implant electronics for integration in a stent craft(2016-02); ; ; ; This paper describes the design, implementation and testing of a wireless blood pressure sensing implant. The implant is mounted on a stent graft. The implant along with the stent graft must fit into a 16F applicator stent delivery system. The implant is powered using the energy harvested from wireless power transmission. The measured pressure data is sent wirelessly to an external data reader hardware. The pressure measurement must have resolution of 1 mmHg.Publicationtype: Conference PaperScopus© Citations 3 386 920