Electrodes for Nerve Recording and Stimulation

New Approach toward Laser-Assisted Modification of Biocompatible Polymers Relevant to Neural Interfacing Technologies

“…Briefly, the fabrication steps of such multielectrode structure are the following: choice of material like an insulator, to provide a good electrical signal with minimum attenuation and crosstalks; metal patterning, which includes an engineering design of the number and size of electrodes, interspace interval between electrodes, wire lines, electrical contact pads, metal conductor, and its electrical characteristics (impedance). Medical grade poly-dimethylsiloxane (PDMS) elastomer is a widely used material in medicine as a carrier material of shunts, pacemakers, and long-term neural implants [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. In the case of the neural implant application, this synthetic polymer is highly preferred for insulator substrate and covering layer for performing stretchable MEAs neural interface devices [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ].…”

“…Medical grade poly-dimethylsiloxane (PDMS) elastomer is a widely used material in medicine as a carrier material of shunts, pacemakers, and long-term neural implants [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. In the case of the neural implant application, this synthetic polymer is highly preferred for insulator substrate and covering layer for performing stretchable MEAs neural interface devices [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. This is the best alternative for the rigid insulator materials [ 1 , 2 , 3 ] (such as silicon dioxide, silicon nitride, or polymers (polyimide, parylene, acrylic imide) with a much higher Young’s modulus than of PDMS).…”

“…In addition, medical grade PDMS elastomers possess high cytocompatibility and biocompatibility, long-term implant life without disruption of the soft tissues (brain, muscles, and nerves), non-toxicity, high gas permeability, chemical stability, non-flammable, high dielectric breakdown, and high optical transparency in the UV-VIS-NIR spectral range. All these remarkable properties have promoted the intensive research and development of PDMS-based MEAs interface devices in basic neuroscience, neural prosthetics, and hybrid bionic systems, connecting the human nervous system with electronic or robotic prostheses [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. Furthermore, all these hi-tech processes have been devoted to partial restoring of the motor and sensor functions (of limbs or organs) or the cognitive functions lost due to disease or trauma.…”

“…Micro-channel tracks of noble metal coatings as electrodes, wires, and pads are among the most commonly used in the coplanar PDMS-based MEAs neural interfacing technologies [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ], because the PDMS polymer provides easy fabrication of MEAs with high-density interconnects and integrated packing. For bioimplants application, thin films of platinum, gold, silver, as well as iridium oxides (IrO x ), have been used for metal patterns, due to their high biocompatibility and corrosion resistivity.…”

“…For bioimplants application, thin films of platinum, gold, silver, as well as iridium oxides (IrO x ), have been used for metal patterns, due to their high biocompatibility and corrosion resistivity. Various innovative approaches [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ], which combined different methods and materials for preparing insulator substrate, its surface activation, and metal patterning, have been applied to produce high-resolution and high-density integrated PDMS-based stretchable MEAs devices for neural and muscular surface interfacing. Usually, the structure processes are complicated and multi-stepped, which include, for example, e-beam or thermal evaporation; electroplating of metal layers; spin coating and cured of the insulating PDMS layers; modification of PDMS surface from hydrophobic to hydrophilic by using oxygen plasma (shadow masks can be used for selective activation); lift-off method of photoresist by applying UV photolithography or ion etching for metal patterning the sample, etc.…”