Fabrication and Characterization of an Active Matrix Thin Film Transistor Array for Intracellular Probing
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Fabrication and characterization of an active matrix thin film transistor array for intracellular probing Seung-Ik Jun, Timothy E. McKnight 1, Anatoli V. Melechko 1, Michael L. Simpson 1, and Philip D. Rack Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996-2200, USA 1 Molecular Scale Engineering and Nanoscale Technologies Research Group, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
ABSTRACT In order to achieve multiple intracellular stimulation and recording devices with high electrode density and low manufacturing cost, we have fabricated and characterized an active matrix thin film transistor array with integrated vertically aligned carbon nanofibers. This device has the potential for cell probing and screening that provides great potential to execute direct cell sensing/probing and recording with a high electrode density. Each unit pixel in the array is individually addressed by a thin film transistor (TFT) and the vertically aligned carbon nanofibers (VACNF) used to impale the cell are fabricated on the drain electrode of the TFT. The VACNF is grown by direct current plasma enhanced chemical vapor deposition (DCPECVD) using a nickel catalyst. Electroanalysis or impedance differences between the cell probing site and a reference electrode are recorded with a potentiostat or a semiconductor analyzer connected to the output terminals. Additionally, the impedance change with frequency of the intracellular probe can be measured by applying a frame signal input and the signal can be recorded in storage capacitors after the frame scan of the TFTs. Consequently, actively addressed nanofiber arrays enable bidirectional interfacing with tissue matrices in a format that provides intercellular positioning of electrode elements as well as the potential for intracellular residence of probes within individual cells. In our research, we exploit these non-planar electrode systems for efficient coupling with excitable cell matrices as well as for intracellular biochemical manipulation and sensing of and delivery to single cells. In this paper, we will discuss the fabrication sequence of the inverted metal-oxide-semiconductor (MOS) TFT, and will elaborate the materials issues related to integrating the carbon nanofibers with the TFT.
INTRODUCTION Microelectrode arrays (MEA) have been studied to explore electrogenic cells and tissues by intra/extracelluar stimulating and recording. In these days MEA based on microelectronic technologies provides direct measurement of cells [1,2]. For higher probing performance, Offenhausser et al. reported a device fabricated with field effect transistors for intracellular recording [2]. Each microelectrode used for stimulating and recording cells was driven by field effect transistors fabricated on a silicon wafer. The main drawback of this device was the extremely low density of electrodes because the electrodes were fabricated at the center region of the device and connected with metallization to the field effect transistors a
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