title: Thiol-ene/acrylate substrates for softening intracortical electrodes.
abstract: Neural interfaces have traditionally been fabricated on rigid and planar substrates, including silicon and engineering thermoplastics. However, the neural tissue with which these devices interact is both 3D and highly compliant. The mechanical mismatch at the biotic-abiotic interface is expected to contribute to the tissue response that limits chronic signal recording and stimulation. In this work, novel ternary thiol-ene/acrylate polymer networks are used to create softening substrates for neural recording electrodes. Thermomechanical properties of the substrates are studied through differential scanning calorimetry and dynamic mechanical analysis both before and after exposure physiological conditions. This substrate system softens from more than 1 GPa to 18 MPa on exposure to physiological conditions: reaching body temperature and taking up less than 3% fluid. The impedance of 177 µm(2) gold electrodes electroplated with platinum black fabricated on these substrates is measured to be 206 kΩ at 1 kHz. Specifically, intracortical electrodes are fabricated, implanted, and used to record driven neural activity. This work describes the first substrate system that can use the full capabilities of photolithography, respond to physiological conditions by softening markedly after insertion, and record driven neural activity for 4 weeks.
authors.affiliation: The University of Texas at Dallas, Department of Materials Science and Engineering, Richardson, Texas.
authors.forename: Taylor
authors.initials: T
authors.lastname: Ware
authors.forename: Dustin
authors.initials: D
authors.lastname: Simon
authors.forename: Clive
authors.initials: C
authors.lastname: Liu
authors.forename: Tabassum
authors.initials: T
authors.lastname: Musa
authors.forename: Srikanth
authors.initials: S
authors.lastname: Vasudevan
authors.forename: Andrew
authors.initials: A
authors.lastname: Sloan
authors.forename: Edward W
authors.initials: EW
authors.lastname: Keefer
authors.forename: Robert L
authors.initials: RL
authors.lastname: Rennaker
authors.forename: Walter
authors.initials: W
authors.lastname: Voit
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000818:Animals; D001303:Auditory Cortex / Q000502:physiology; D001672:Biocompatible Materials / Q000737:chemistry; D057005:Bioengineering; D002478:Cells, Cultured; D004567:Electrodes, Implanted; D004867:Equipment Design; D008422:Materials Testing; D051379:Mice; D009474:Neurons / Q000502:physiology; D051381:Rats
chemical_list: D000180:Acrylic Resins; D001672:Biocompatible Materials; C006903:carbopol 940
keywords: intracortical electrode; neural interface; plasticization; smart polymer; thiol-ene