Polyimide-based intracortical neural implant with improved structural stiffness

Kee Keun Lee, Jiping He, Amarjit Singh, Stephen Massia, Gholamreza Ehteshami, Bruce Kim, Gregory Raupp

Research output: Contribution to journalArticlepeer-review

142 Scopus citations


A novel structure for chronically implantable cortical electrodes using polyimide bio-polymer was devised, which provides both flexibility for micro-motion compliance between brain tissues and the skull and at the brain/implant interface and stiffness for better surgical handling. A 5-10 μm thick silicon backbone layer was attached to the tip of the electrode to enhance the structural stiffness. This stiff segment was then followed by a 1 mm flexible segment without a silicon backbone layer. The fabricated implants have tri-shanks with five recording sites (20 μm × 20 μm) and two vias of 40 μm × 40 μm on each shank. In vitro cytotoxicity tests of prototype implants revealed no adverse toxic effects on cells. Bench test impedance values were assessed, resulting in an average impedance value of ∼2 MΩ at 1 KHz. For a 5 μm thick silicon backbone electrode, the stiffness of polyimide-based electrodes was increased ten times over that of electrodes without the silicon backbone layer. Furthermore, polyimide-based electrodes with 5 μm and 10 μm thick silicon backbone layer penetrated pia of rat brain without buckling that has been observed in implants without silicon reinforcement.

Original languageEnglish (US)
Pages (from-to)32-37
Number of pages6
JournalJournal of Micromechanics and Microengineering
Issue number1
StatePublished - Jan 1 2004

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Mechanics of Materials
  • Mechanical Engineering
  • Electrical and Electronic Engineering


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