Project 2:

Novel material and design for next generation neural electrodes (focusing on size and mechanics)

  • Accumulated evidences suggest that the size and mechanical properties of the implant play a significant role in causing the sustained reactive tissue responses. Therefore, we are exploring new materials and novel electrode designs that may be less invasive and better mimic the brain tissue mechanical properties. We have several projects along this line and some of these projects are in collaboration with external researchers. The first project test the hypothesis that much of the tissue inflammation is caused by the mechanical mismatch between the stiff electrode arrays (currently made of silicon, metal and tough polymer substrates) and the soft brain tissue.  In collaboration TDA research, we synthesize electrically conducting materials that have mechanical modulus similar to brain tissue. We showed microglia activation towards the softwire prototypes is significantly reduced. After successful development of an implantation technique for such soft implant, we have demonstrated the functionality of such novel electrodes in recording and stimulation in vivo. In another collaborative project, a team of CMU mechanical/electrical engineers led by Dr. Gary Fedder is building a new generation of neural probes that are ultrasmall (below 7 m) and ultra-compliant. The insertion of such device is facilitated by biodissovable and biocompatible carboxymethylcellulose (CMC). Tissue heals and regenerates completely around the dissolving implant indicating great potential of this electrode design. Lastly, we are building upon the carbon fiber Microthread electrodes, first published in Nature Materials, to engineer next generation wireless stimulation and drug delivery Microthread Electrodes as well as PNS and end-organ electrophysiology and chemical sensing carbon fiber Microthread Electrodes. 

Example publications include:

  • Christi L. Kolarcik, Silvia D. Lubben, Shawn A. Sapp, Jenna Hanner, Noah Snyder, Takashi D. Y. Kozai, Emily Chang, James A. Nabity, Shawn T. Nabity, Carl F. Lagenaure, X. Tracy Cui, Elastomeric and soft conducting microwires for implantable neural interfaces, Soft Matter, 2015, 4(9) 1408-1416; DOI: 10.1039/C5SM00174A
  • Takashi D. Y. Kozai, Zhannetta Gugel, Xia Li, Peter J. Gilgunn, Rakesh Khilwani, O. Burak Ozdoganlar, Gary K. Fedder, Doug J. Weber, X. Tracy Cui, Chronic tissue response to carboxymethyl cellulose based dissolvable insertion needle for ultra-small neural probes, Biomaterials, Volume 35, Issue 34, November 2014, Pages 9255–9268
  • Gilgunn PJ, Khilwani R, Kozai TDY, Weber DJ, Cui XT, Erdos G, Ozdoganlar OB, Fedder GK. An ultra-compliant, scalable neural probe with molded biodissolvable delivery vehicle. Micro Electro Mechanical Systems (MEMS), IEEE 25th International Conference on 2012, 56-59.
  • Kozai TDY, Langhals NB, Patel PR, Deng X, Zhang H, Lahann J, Kotov N, Kipke DR. Ultrasmall implantable composite microelectrodes with bioactive surfaces for chronic neural interfaces. Nature Materials. 2012 11(12), 1065-1073. 
  • Du Z, Kolarcik CL, Kozai TDY, Luebben SD, Sapp SA, Zheng XS, Nabity JA, Cui XT. Ultrasoft microwire neural electrodes improve chronic tissue integration. Acta Biomaterialia. 2017

Novel material and design for next generation neural electrodes