title: A fiber-based implantable multi-optrode array with contiguous optical and electrical sites.
abstract: OBJECTIVE
  Although various kinds of optrodes are designed to deliver light and sense electrophysiological responses, few have a tightly closed optical delivering site or electrical recording site. The large space between them often blurs the stimulation location and light intensity threshold.
  
  
  METHODS
  Based on an optical fiber, we develop an optrode structure which has a coniform tip where the light exit point and gold-based electrode site are located. The optrode is fabricated by integrating a metal membrane electrode on the outside of a tapered fiber. Half of the cone-shape tip is covered by a layer of gold membrane to form the electrode. A commercial fiber connector, mechanical transfer (MT) module, is chosen to assemble the multi-optrode array (MOA). The MT connector acts as both the holder of the optrode array and an aligning part to connect the MOA with the light source.
  
  
  RESULTS
  We fabricated a pluggable MOA weighing only 0.2 g. The scanning electron microscope images showed a tight cover of the metal layer on the optrode tip with an exposure area of 1500 µm(2). The electrochemical impedance of the optrode at 1 kHz was 100 kΩ on average and the light emission intensity reached 13 mW. The optical modulating and electrophysiological recording ability of the MOA was validated by monitoring the response of cells in a ChR2-expressing mouse's cerebral cortex. Neurons that maintained high cluster quality (signal-to-noise ratio = 5:1) and coherence in response to trains of 20 Hz stimulation were monitored.
  
  
  CONCLUSIONS
  The optrode array reduces the distance between the optical stimulating sites and electrophysiological sites dramatically and can supply multiple channels to guide different lights simultaneously. This optrode with its novel structure may lead to a different kind of optical neural control prosthetic device, opening up a new option for neural modulation in the brain.
authors.affiliation: State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, People's Republic of China.
authors.forename: Sanyuan
authors.initials: S
authors.lastname: Chen
authors.forename: Weihua
authors.initials: W
authors.lastname: Pei
authors.forename: Qiang
authors.initials: Q
authors.lastname: Gui
authors.forename: Yuanfang
authors.initials: Y
authors.lastname: Chen
authors.forename: Shanshan
authors.initials: S
authors.lastname: Zhao
authors.forename: Huan
authors.initials: H
authors.lastname: Wang
authors.forename: Hongda
authors.initials: H
authors.lastname: Chen
mesh_terms: D000200:Action Potentials / Q000502:physiology* / Q000528:radiation effects; D000818:Animals; D002540:Cerebral Cortex / Q000502:physiology* / Q000528:radiation effects; D004567:Electrodes, Implanted; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D008027:Light; D051379:Mice; D062308:Optogenetics / Q000295:instrumentation*; D010775:Photic Stimulation / Q000295:instrumentation*