All Titanium Microelectrode Array for Field Potential Measurements from Neurons and Cardiomyocytes—A Feasibility Study

Abstract

Abstract:In this paper, we describe our all-titanium microelectrode array (tMEA) fabrication process and show that uncoated titanium microelectrodes are fully applicable to measuring field potentials (FPs) from neurons and cardiomyocytes. Many novel research questions require custom designed microelectrode configurations different from the few commercially available ones. As several different configurations may be needed especially in a prototyping phase, considerable time and cost savings in MEA fabrication can be achieved by omitting the additional low impedance microelectrode coating, usually made of titanium nitride (TiN) or platinum black, and have a simplified and easily processable OPEN ACCESSMicromachines 2011, 2 395 MEA structure instead. Noise, impedance, and atomic force microscopy (AFM) characterization were performed to our uncoated titanium microelectrodes and commercial TiN coated microelectrodes and were supplemented by FP measurements from neurons and cardiomyocytes on both platforms. Despite the increased noise levels compared to commercial MEAs our tMEAs produced good FP measurements from neurons and cardiomyocytes. Thus, tMEAs offer a cost effective platform to develop custom designed electrode configurations and more complex monitoring environments.

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“…The lower noise results for TiN microelectrodes is supported by visual assessment of the cell experiment data shown in Fig. 4 and also by our earlier results, 8 where in specific noise measurements, the rms noise of TiN microelectrodes was measured to be just 2.7 lV with very little deviation.…”

“…4(c)] microelectrodes. However, as reported earlier, 8 neuronal signal strength increases along with increasing noise levels, so signaling is still easily observable for microelectrode types having higher noise levels.…”

“…Using tapping mode, 256 Â 256 pixel scans were taken over a 1 lm Â1 lm area, and surface area ratio and surface roughness [root mean square (rms)] were calculated with XEI software (Park Systems). Due to the small, pillarlike structure of the microelectrode surface of cMEAs, evaluating a TiN surface with AFM was found unreliable in our earlier study 8 and thus only sMEAs were evaluated using AFM for this experiment.…”

“…They consisted of a glass substrate, titanium as the base conducting material for microelectrodes, contact pads and tracks between them, and Si 3 N 4 as the insulator layer as described by Ryynänen et al 8 Next, the sMEAs were spin coated with an approximately 2.5 lm thick photoresist layer (ma-P 1225, micro resist technology GmbH, Berlin, Germany). Openings were made above the leftmost 29 microelectrodes of the 58 microelectrodes, and above the two bigger electrodes and all the contact pads using normal lithographic procedures.…”

Technical feasibility study for production of tailored multielectrode arrays and patterning of arranged neuronal networks

“…Besides its protective function, Ti 2 N is known to form a columnar microstructure, hence reducing the impedance of the electrodes. This will reduce their thermal noise in comparison to even Ti electrodes [ 29 ] and enhance charge transfer capability [ 30 ]. Silicon nitride is used as the insulating material on top of the MEA, its transparency making it suitable for microscopic investigation of the neurons cultured on the MEA.…”