Browsing by Subject "Polyimide"
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Item Flexible polyimide based 34-channel electrode arrays for mouse EEG measurement(SPIE, 2019-05-02) Chowdhury, Fatima Nafisa; Sood, Rachit; Nam, Hyungwoo; Lobo, Mary Kay; Choa, Fow-SenElectroencephalogram (EEG) recording is a widely used method to measure electrical activity in the brain. Rodent EEG brain recording not only is noninvasive but also has the advantages to accomplish full brain monitoring, compared with that of the invasive techniques like micro-electrode-arrays. In comparison to other noninvasive recording techniques, EEG is the only technique that can achieve sub-ms scale time resolution, which is essential to obtain causal relationship. In this work, we demonstrated a simple microfabrication process for developing a high-density polyimide-based rodent EEG recording cap. A 34-channel rodent electrode array with a total size of 11mmx8mm, individual electrode diameter 240μm and interconnect wire linewidth 35μm was designed and fabricated. For the fabrication process, we first deposit 350nm SiO2 on a silicon substrate. We then fabricate 6-7μm thick first layer polyimide caps with fingers and contact holes. Gold deposition and then lithography etching of 34 channel contact-electrodes and their interconnects were fabricated in the second step. The third step was to cover metal interconnects with a 10μm thick second layer polyimide, which was fabricated with photolithography before the final film released by HF undercutting etching of SiO2 layer. Then the fabricated EEG cap is interfaced with a commercial 34-channel female connector, which is soldered with 34-line wires. These wires are then connected to an ADC to record the EEG data in computer for post-processing. With polyimide, the EEG cap is biocompatible, and flexible which makes it suitable for good contact with rodent skulls.Item Flexible Polyimide based 34-channel Electrode Arrays for Mouse EEG Measurement(2019-01-01) Chowdhury, Fatima Nafisa; Choa, Fow-Sen; Computer Science and Electrical Engineering; Engineering, ElectricalElectroencephalogram (EEG) recording is a widely used method to measure electrical activity in the brain. Unlike other noninvasive recording techniques, EEG technique allows sub-ms scale time resolution, which is essential to obtain causal relationship. In this work, we demonstrated a microfabrication process for developing a high-density polyimide-based rodent EEG recording cap. A 34-channel rodent electrode array with a total size of 11mmx8mm, individual electrode diameter 240�m and interconnect wire linewidth 35�m, was designed and fabricated. For the fabrication process, a silicon substrate was used and polyimide caps were fabricated. Gold deposition and lithography etching of 34-channel contact-electrodes, along with interconnects, was completed as next step. Fully developed EEG cap was then interfaced with a 34-channel female connector, which will then be connected to an ADC for acquisition and post-processing. This polyimide based EEG cap is biocompatible and flexible, and therefore, suitable for good contact with rodent skulls and non-invasive recording.Item Kapton Polyimide-Based EEG Microelectrode Array and Interfaces for Mice Brainwave Recordings and Analysis(SPIE, 2018) Gupta, D.; Islam, M.; Nam, H.; Lobo, M. K.; Choa, F. S.There is a rise in the study of functional connectivity among various cortical regions and investigations to uncover causal links between a stimulus and the corresponding neural dynamics through electrophysiological imaging of the human brain. Animal model that exhibit simplistic representations of such networks open a doorway for such investigations and are gaining rapid popularity. In this study, we investigate and compare resting state network and auditory stimulus related activity with minimal invasive technology along computational spectral analysis on a C57/BL6 based mouse model. Somatosensory, motor and visual cortex are observed to be highly active and significantly correlated (p-value<0.05). Moreover, given the spatial limitation due to small size of the mouse head, we also describe a low-cost and effective fabrication process for the mouse EEG Polyimide Based Microelectrodes (PBM) array. The easy-to-implement fabrication process involves transfer of the pattern on a copper layer of the Kapton film followed by gold electroplating and application of insulation paint. Acoustic stimulation is done by using tube extensions for avoiding electrical coupling to EEG signals. Unlike multi-electrode array type of invasive methods that are local to a cortical region, the methods established in this study can be used for examining functional connectivity analysis, neural dynamics and cortical response at a global level.