Impedance Measurements on a Multi-functional Neural MEA Platform
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1
ETH Zurich, Department of Biosystems Science and Engineering, Switzerland
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2
ETH Zurich, Department of Biosystems Science and Engineering, Switzerland
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3
ETH Zurich, Department of Biosystems Science and Engineering, Switzerland
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4
ETH Zurich, Department of Biosystems Science and Engineering, Switzerland
Motivation
Simultaneous electrical recording and impedance measurement on a HDMEA enable to study electrophysiology as well as morphology or viability of neuronal cells. In order to do such measurements, a multi-functional recording platform is required, which can control the HDMEA and extract desired output parameters.
Material and Methods
The new multi-functional CMOS MEA includes 32 channels for impedance measurements and 2048 action-potential recording channels [1]. To measure the impedance of neuronal tissue, an on-chip generated sinusoidal voltage was applied between the reference electrode and 32 arbitrary selected microelectrodes. A “CmdSender” program was developed in C#, which can configure the channels, as wells as the electrode array. USB data from the CmdSender output were converted to parallel data by using a UM245R chip and then buffered in an FPGA, which eventually sent the commands in SPI format to the MEA chip. Integrated lock-in amplifiers were used to measure the impedance of neuronal tissue over a wide frequency range from 1Hz to 1MHz. Signals from these amplifiers were then digitized with delta-sigma converters, and the output bit stream was acquired using an NI PXIe-6544 High Speed DAQ card. A LabVIEW program is implemented to get the acquired bit stream of every channel and to apply a cascaded integrator-comb (CIC) filter for extracting the desired signals. In-phase and quadrature components of the impedance are then can be calculated as the dc value of these extracted signals.
Results
Different commands could be easily sent to the chip by using the CmdSender program, and output signals could be extracted through the implemented LabVIEW program. A frequency spectrum of an output signal, which was obtained for a 1 kHz input signal, shows that the output signal only had a 1 kHz component and the higher frequency components were filtered out properly.
Conclusion
A bidirectional measurement platform was implemented to configure on-chip registers and to extract impedance signals from a multi-functional CMOS MEA. Spectrum analysis showed that the output signal had the same main frequency component as the test sinusoidal voltage.
References
V. Viswam et al., "Multi-functional microelectrode array system featuring 59’760 electrodes, 2048 electrophysiology channels, impedance, and neurotransmitter measurement units", ISSCC 2016, Session 22.8, Digest of Technical Papers, pp. 394-396 (ISBN 978-1-4673-9467-3).
Acknowledgements
Financial support through the ERC Advanced Grant 267351 “NeuroCMOS” and individual support for A. Shadmani through the FP7-MTN “EngCaBra” (Contract 264417) are acknowledged.
Keywords:
CMOS,
Impedance measurement,
Multi-functional,
HDMEA
Conference:
MEA Meeting 2016 |
10th International Meeting on Substrate-Integrated Electrode Arrays, Reutlingen, Germany, 28 Jun - 1 Jul, 2016.
Presentation Type:
Poster Presentation
Topic:
MEA Meeting 2016
Citation:
Bounik
R,
Viswam
V,
Shadmani
A,
Dragas
J,
Müller
J,
Chen
Y and
Hierlemann
A
(2016). Impedance Measurements on a Multi-functional Neural MEA Platform.
Front. Neurosci.
Conference Abstract:
MEA Meeting 2016 |
10th International Meeting on Substrate-Integrated Electrode Arrays.
doi: 10.3389/conf.fnins.2016.93.00025
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Received:
22 Jun 2016;
Published Online:
24 Jun 2016.
*
Correspondence:
Dr. Raziyeh Bounik, ETH Zurich, Department of Biosystems Science and Engineering, Basel, Switzerland, raziyeh.bounik@bsse.ethz.ch