Gold coated SU-8-based microelectrodes for in vivo electrophysiological studies: Rapid prototyping protocol-specific microelectrode designs

Microelectrodes are widely used to record biological signals from living tissue, namely in neuroscience where researches need to record brain signals in vivo. Several types of microelectrodes are available in the market. Unfortunately, most of the microelectrode developing processes are time consuming and expensive. This work presents a rapid low-cost prototyping technology for protocol-specific microelectrode designs. The suggested fabrication process combines SU-8 photoresist patterning in multiple layers with the deposition of intermediate conductive layers (Au layer in the presented case). The fabricated microelectrodes were specifically designed for an electrophysiological experiment that required simultaneous recording in the pre-frontal cortex (PFC) and stimulation in the hippocampus of the rat brain. After electrode implantation surgery in an anesthetized rat, local-field potentials (LFP) from the PFC were acquired. The power spectra of the LFPs using the SU-8-based microelectrode and using a commercially available Pt-Ir electrode are comparable in a great extent. Staining of perfusion fixed brain slices showed that the electrodes targeted the correct brain regions. SU-8-based microelectrodes appear to be valuable as a rapid prototyping technology to design low-cost protocol-specific microelectrodes.