Integrated wireless neural interface based on the Utah electrode array


This report presents results from research towards a fully integrated, wireless neural interface consisting of a 100-channel microelectrode array, a custom-designed signal processing and telemetry IC, an inductive power receiving coil, and SMD capacitors. An integration concept for such a device was developed, and the materials and methods used to implement this concept were investigated. We developed a multi-level hybrid assembly process that used the Utah Electrode Array (UEA) as a circuit board. The signal processing IC was flip-chip bonded to the UEA using Au/Sn reflow soldering, and included amplifiers for up to 100 channels, signal processing units, an RF transmitter, and a power receiving and clock recovery module. An under bump metallization (UBM) using potentially biocompatible materials was developed and optimized, which consisted of a sputter deposited Ti/Pt/Au thin film stack with layer thicknesses of 50/150/150 nm, respectively. After flip-chip bonding, an underfiller was applied between the IC and the UEA to improve mechanical stability and prevent fluid ingress in in vivo conditions. A planar power receiving coil fabricated by patterning electroplated gold films on polyimide substrates was connected to the IC by using a custom metallized ceramic spacer and SnCu reflow soldering. The SnCu soldering was also used to assemble SMD capacitors on the UEA. The mechanical properties and stability of the optimized interconnections between the UEA and the IC and SMD components were measured. Measurements included the tape tests to evaluate UBM adhesion, shear testing between the Au/Sn solder bumps and the substrate, and accelerated lifetime testing of the long-term stability for the underfiller material coated with a a-SiCx:H by PECVD, which was intended as a device encapsulation layer. The materials and processes used to generate the integrated neural interface device were found to yield a robust and reliable integrated package.

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9
Fig. 10
Fig. 11
Fig. 12
Fig. 13
Fig. 14
Fig. 15
Fig. 16


  1. J. Aziz, R. Genov, M. Derchansky, B. Bardakjian, P. Carlen, 256-Channel Neural Recording Microsystem with On-Chip 3D Electrodes. In Proceedings of 2007 IEEE International Solid-State Circuits Conference, 160–161, 594, San Francisco, CA, USA (2007)

  2. A. Branner, R.B. Stein, E. Fernandez, Y. Aoyagi, R.A. Normann, Long-term stimulation and recording with a penetrating microelectrode array in cat sciatic nerve IEEE Trans. Biomed. Eng. 51, 146–157 (2004). doi:10.1109/TBME.2003.820321

    Article  Google Scholar 

  3. P.K. Campbell, K.E. Jones, R.J. Huber, K.W. Horch, R.A. Normann, A silicon-based, three-dimensional neural interface: manufacturing processes for an intra cortical electrode array IEEE Trans. Biomed. Eng 38, 758–768 (1991). doi:10.1109/10.83588

    Article  Google Scholar 

  4. C.A. Chestek, V. Gilja, R.J. Kier, P. Nuyujukian, S.I. Ryu, F. Solzbacher, R. Harrison, K.V. Shenoy, C. Hermes, RF wireless low-power neural recording system for freely-behaving primates. In Proc. of the 2008 IEEE International Symposium on Circuits and Systems (ISCAS 2008), Seattle, Washington (2008)

  5. G.A. DeMichele, P.R. Troyk, Integrated multichannel wireless biotelemetry system. In Proc. 25th Int. IEEE-EMBS Conf., 3372–3375, Cancun, Mexico (2003)

  6. S. Farshchi, P. Nuyujukian, A. Pesterev, I. Mody, J.W. Judy, A. Tiny, OS enabled MICA2-based wireless neural interface IEEE Trans. Biomed. Eng. 53, 1416–1424 (2006). doi:10.1109/TBME.2006.873760

    Article  Google Scholar 

  7. M.D. Gingerich, J.F. Hetke, D.J. Anderson, K.D. Wise, A 256-site 3-D CMOS microelectrode array for multipoint stimulation and recording in the central nervous system. In Proc. Int. Conf. Solid-State Sensors and Actuators, 416–419, Munich, Germany (2001)

  8. R. Hahn, A. Kamp, A. Ginolas, M. Schmidt, J. Wolf, V. Glaw, M. Töpper, O. Ehrmann, H. Reichl, High power multichip modules employing the planar embedding technique and microchannel water heat sinks IEEE Trans. Compon. Pack. A 20, 432–441 (1997)

    Article  Google Scholar 

  9. R.R. Harrison, P.T. Watkins, R.J. Kier, R.O. Lovejoy, D.J. Black, B. Greger, F. Solzbacher, A low-power integrated circuit for a wireless100-electrode neural recording system IEEE J. Solid-State Circuits 42, 123–133 (2007a). doi:10.1109/JSSC.2006.886567

    Article  Google Scholar 

  10. R.R. Harrison, P.T. Watkins, R.J. Kier, D.J. Black, R.O. Lovejoy, R.A. Normann, F. Solzbacher, Design and testing of an integrated circuit for multi-electrode neural recording. In Proceedings of the 20th International Conference on VLSI Design (VLSID 2007), Bangalore, India (2007b)

  11. R.R. Harrison, R.J. Kier, C.A. Chestek, V. Gilja, P. Nuyujukian, S.I. Ryu, B. Greger, F. Solzbacher, K.V. Shenoy, Wireless neural signal acquisition with single low-power integrated circuit. In Proc. of the 2008 IEEE International Symposium on Circuits and Systems (ISCAS 2008), Seattle, Washington (2008)

  12. J.L. Hill, D.E. Culler, Mica: a wireless platform for deeply embedded networks IEEE Micro 22, 12–24 (2002). doi:10.1109/MM.2002.1134340

    Article  Google Scholar 

  13. L.R. Hochberg, M.D. Serruya, G.M. Friehs, J.A. Mukand, M. Saleh, A.H. Caplan, A. Branner, D. Chen, R.D. Penn, J.P. Donoghue, Neuronal ensemble control of prosthetic devices by a human with tetraplegia Nature 442, 164–171 (2006). doi:10.1038/nature04970

    Article  Google Scholar 

  14. A.C. Hoogerwerf, K.D. Wise, A three-dimensional microelectrode array for chronic neural recording IEEE Trans. Biomed. Eng. 41, 1136–1146 (1994). doi:10.1109/10.335862

    Article  Google Scholar 

  15. J.-M. Hsu, L. Rieth, S. Kammer, K.P. Koch, R.A. Normann, F. Solzbacher, PECVD a-SiC:H and Parylene encapsulation for chronically implanted neural recording devices. NIH/NINDS Neural Interfaces Workshop, Bethesda, MD, USA (2005)

  16. J.-M. Hsu, P. Tathireddy, L. Rieth, R.A. Normann, F. Solzbacher, Characterization of a-SiCx:H thin films as an encapsulation material for integrated silicon based neural interface devices Thin. Solid. Films 516, 34–41 (2007). doi:10.1016/j.tsf.2007.04.050

    Article  Google Scholar 

  17. J.-M. Hsu, L. Rieth, R.A. Normann, P. Tathireddy, F. Solzbacher, Hermetic encapsulation of an integrated neural interface device with Parylene-C. IEEE Trans. Biomed. Eng. (2008a) accepted for publication

  18. J.-M. Hsu, L. Rieth, S. Kammer, M. Orthner, F. Solzbacher, Influence of thermal and deposition processes on the surface morphology, crystallinity, and adhesion of Parylene-C Sens. Mater. 20, 071–086 (2008b)

    Google Scholar 

  19. M. Hutter, H. Hohnke, H. Oppermann, M. Klein, G. Engelmann, Assembly and Reliability of Flip Chip Solder Joints Using Miniaturized Au/Sn Bumps., In Proc. 54th Electronic Components and Technology Conf., Las Vegas, NV, USA (2004)

  20. P. Irazoqui-Pastor, I. Mody, J.W. Judy, Transcutaneous RF-powered neural recording device. In Proc. 24th Annu. Conf./Annu. Fall Meeting Biomedical Engineering Society 3, 2105–2106, Houston, TX, USA (2002)

  21. K.E. Jones, P.K. Campbell, R.A. Normann, A glass/silicon composite intra cortical electrode array Ann. Biomed. Eng. 20, 423–437 (1992). doi:10.1007/BF02368134

    Article  Google Scholar 

  22. C. Kim, K.D. Wise, A 64-site multishank CMOS low-profile neural stimulating probe IEEE J. Solid-State Circuits 31, 1230–1238 (1996). doi:10.1109/4.535406

    Article  Google Scholar 

  23. S. Kim, K. Zoschke, M. Klein, D. Black, K. Buschick, M. Toepper, P. Tathireddy, R. Harrison, H. Oppermann, F. Solzbacher, Switchable polymer based thin film coils as a power module for wireless neural interfaces Sensors Actuators A 136, 467–474 (2007). doi:10.1016/j.sna.2006.10.048

    Article  Google Scholar 

  24. D.R. Kipke, R.J. Vetter, J.C. Williams, J.F. Hetke, Silicon-substrate intracortical microelectrode arrays for long-term recording of neuronal spike activity in cerebral cortex IEEE Trans. Neural Syst. Rehabil. Eng. 11, 151–155 (2003). doi:10.1109/TNSRE.2003.814443

    Article  Google Scholar 

  25. S. Martel, N. Hatsapoulos, I. Hunter, J. Donoghue, J. Burger, J. Malasek, C. Wiseman, R. Dyer, Development of a Wireless Brain Implant: the Telemetric Electrode Array System (TEAS) Project. In Proceedings of the 23rd Annual EMBS International Conference, Istanbul, Turkey (2001)

  26. M. Modarreszadeh, R.N. Schmidt, Wireless, 32-channel, EEG and epilepsy monitoring system. In Proc. 19th Int. Conf. IEEE/EMBS, 1157–1160, Chicago, IL, USA (1997)

  27. P. Mohseni, K. Najafi, A wireless FM multichannel microsystem for biomedical neural recording applications. In Proc. IEEE Southwest Symp. Mixed Signal Design, 217–222, Tucson, AZ, USA (2003)

  28. P. Mohseni, K. Najafi, Wireless multichannel biopotential recording using an integrated FM telemetry circuit. In Proc. 26th Annu. Int. Conf. Engineering in Medicine and Biology Soc., 4083–4086, San Francisco, CA, USA (2004)

  29. A. Nieder, Miniature stereo radio transmitter for simultaneous recording of multiple single-neuron signals from behaving owls J. Neurosci. Methods 101, 157–164 (2000). doi:10.1016/S0165-0270(00)00263-6

    Article  Google Scholar 

  30. I. Obeid, M.A.L. Nicolelis, P.D. Wolf, A multichannel telemetry system for single unit neural recordings J. Neurosci. Methods 133, 33–38 (2004). doi:10.1016/j.jneumeth.2003.09.023

    Article  Google Scholar 

  31. J. Parramon, P. Doguet, D. Martin, M. Verleyssen, R. Munoz, L. Leija, E. Valderrama, ASIC-based batteryless implantable telemetry microsystem for recording purposes. In Proc. 19th Int. IEEE-EMBS Conf., 2225–2228, Chicago, IL, USA (1997)

  32. W.R. Patterson, Y.-K. Song, C.W. Bull, I. Ozden, A.P. Deangellis, C. Lay, J.L. McKay, A.V. Nurmikko, J.D. Donoghue, B.W. Connors, A microelectrode/microelectronic hybrid device for brain implantable neuroprosthesis applications IEEE Trans. Biomed. Eng. 51, 1845–1853 (2004). doi:10.1109/TBME.2004.831521

    Article  Google Scholar 

  33. P.J. Rousche, R.A. Normann, Chronic recording capability of the Utah Intracortical Electrode Array in cat sensory cortex J. Neurosci. Methods 82, 1–15 (1998). doi:10.1016/S0165-0270(98)00031-4

    Article  Google Scholar 

  34. P.J. Rousche, R.A. Normann, Chronic intracortical microstimulation (ICMS) of cat sensory cortex using the utah intracortical electrode array IEEE Trans. Rehabil. Eng. 7, 56–68 (1999). doi:10.1109/86.750552

    Article  Google Scholar 

  35. G. Santhanam, S.I. Ryu, B.M. Yu, A. Afshar, K.V. Shenoy, A high-performance brain-computer interface Nature 442, 195–198 (2006). doi:10.1038/nature04968

    Article  Google Scholar 

  36. H.J. Song, D.R. Allee, K.T. Speed, Single chip system for bio-data acquisition, digitization and telemetry In Proc. 1997 IEEE Int. Symp. Circuits Systems 3, 1848–1851 (1997)Hong Kong

    Google Scholar 

  37. Y.-K. Song, W.R. Patterson, C.W. Bull, D.A. Borton, Y. Li, A.V. Nurmikko, J.D. Simeral, J.D. Donoghue, A brain implantable microsystem with hybrid RF/IR telemetry for advanced neuroengineering applications. In Proceedings of the 29th Annual International Conference of the IEEE EMBS, 445-448, Lyon, France (2007)

  38. T. Stieglitz, H. Beutel, M. Schuettler, J.-U. Meyer, Micromachined, polyimide-based devices for flexible neural interfaces Biomed. Microdevices 2, 283–294 (2000). doi:10.1023/A:1009955222114

    Article  Google Scholar 

  39. T. Stieglitz, M. Schuettler, K.P. Koch, Implantable biomedical microsystems for neural prostheses IEEE Eng. Med. Biol. Mag. 24, 58–65 (2005). doi:10.1109/MEMB.2005.1511501

    Article  Google Scholar 

  40. S. Takeuchi, I. Shimoyama, A radio-telemetry system with a shape memory alloy microelectrode for neural recording of freely moving insects IEEE Trans. Biomed. Eng. 51, 133–137 (2004). doi:10.1109/TBME.2003.820310

    Article  Google Scholar 

  41. M.E. Thomas, M.P. Hartnett, J.E. McKay, The use of surface profilometers for the measurement of wafer curvature J. Vac. Sci. Technol. A 6, 2570–2571 (1998). doi:10.1116/1.575550

    Article  Google Scholar 

  42. M. Töpper, J. Wolf, V. Glaw, K. Buschick, A. Dabek, L. Dietrich, O. Ehrmann, H. Reichl, MCM-D with Embedded Active and Passive Components. In Proceedings ISHM 1996, Minneapolis, USA (1996)

  43. M. Töpper, K. Buschick, J. Wolf, V. Glaw, R. Hahn, A. Dabek, O. Ehrmann, H. Reichl, Embedding Technology—A Chip-First Approach using BCB. In Proc. of the 3rd International Symposium on Advanced Packaging Materials, 11–14 (1997)

  44. M. Töpper, D. Tönnies, Microelectronic Packaging, in Semiconductor Fabrication Handbook, ed. by M.H. Geng (McGraw-Hill, 2005), pp. 21.1–21.54

  45. K.D. Wise, D.J. Anderson, J.F. Hetke, D.R. Kipke, K. Najafi, Wireless implantable microsystems: high-density electronic interfaces to the nervous system Proc. IEEE 92, 76–97 (2004). doi:10.1109/JPROC.2003.820544

    Article  Google Scholar 

  46. Y. Yao, M.N. Gulari, J.F. Hetke, K.D. Wise, A self-testing multiplexed CMOS stimulating probe for a 1024-site neural prosthesis. In Proc. IEEE Int. Conf. Solid-State Sensors and Actuators, 1213–1216, Boston, MA, USA (2003)

  47. Y. Yao, M.N. Gulari, J.A. Wiler, K.D. Wise, A microassembled low-profile three-dimensional microelectrode array for neural prosthesis applications J. Microelectromech. Syst. 16, 977–988 (2007). doi:10.1109/JMEMS.2007.896712

    Article  Google Scholar 

Download references


This work was supported in part by NIH/NINDS Contract HHSN265200423621C and by DARPA under Contract N66001-06-C-8005. The authors gratefully acknowledge the colleagues at Fraunhofer IZM for their technical assistance in setup and conducting IC bumping, flip chip bonding and SMD reflow soldering.

Author information



Corresponding author

Correspondence to S. Kim.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Kim, S., Bhandari, R., Klein, M. et al. Integrated wireless neural interface based on the Utah electrode array. Biomed Microdevices 11, 453–466 (2009).

Download citation


  • Utah electrode array (UEA)
  • Neural interface
  • Neural microelectrode
  • Under bump metallization (UBM)
  • Flip chip bonding
  • Hybrid integration