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Micromachines 2016, 7(9), 154; doi:10.3390/mi7090154

Fabrication and Microassembly of a mm-Sized Floating Probe for a Distributed Wireless Neural Interface

1
GT-Bionics lab, School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30308, USA
2
Premitec. Inc., Raleigh, NC 27606, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Kenichi Takahata
Received: 2 July 2016 / Revised: 15 August 2016 / Accepted: 22 August 2016 / Published: 1 September 2016
(This article belongs to the Special Issue Implantable Microsystems)
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Abstract

A new class of wireless neural interfaces is under development in the form of tens to hundreds of mm-sized untethered implants, distributed across the target brain region(s). Unlike traditional interfaces that are tethered to a centralized control unit and suffer from micromotions that may damage the surrounding neural tissue, the new free-floating wireless implantable neural recording (FF-WINeR) probes will be stand-alone, directly communicating with an external interrogator. Towards development of the FF-WINeR, in this paper we describe the micromachining, microassembly, and hermetic packaging of 1-mm3 passive probes, each of which consists of a thinned micromachined silicon die with a centered Ø(diameter) 130 μm through-hole, an Ø81 μm sharpened tungsten electrode, a 7-turn gold wire-wound coil wrapped around the die, two 0201 surface mount capacitors on the die, and parylene-C/Polydimethylsiloxane (PDMS) coating. The fabricated passive probe is tested under a 3-coil inductive link to evaluate power transfer efficiency (PTE) and power delivered to a load (PDL) for feasibility assessment. The minimum PTE/PDL at 137 MHz were 0.76%/240 μW and 0.6%/191 μW in the air and lamb head medium, respectively, with coil separation of 2.8 cm and 9 kΩ receiver (Rx) loading. Six hermetically sealed probes went through wireless hermeticity testing, using a 2-coil inductive link under accelerated lifetime testing condition of 85 °C, 1 atm, and 100%RH. The mean-time-to-failure (MTTF) of the probes at 37 °C is extrapolated to be 28.7 years, which is over their lifetime. View Full-Text
Keywords: free-floating wireless implantable neural recording (FF-WINeR); neural recording; wireless power transmission; mechanical biocompatibility; distributed probes; brain mapping free-floating wireless implantable neural recording (FF-WINeR); neural recording; wireless power transmission; mechanical biocompatibility; distributed probes; brain mapping
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Yeon, P.; Mirbozorgi, S.A.; Ash, B.; Eckhardt, H.; Ghovanloo, M. Fabrication and Microassembly of a mm-Sized Floating Probe for a Distributed Wireless Neural Interface. Micromachines 2016, 7, 154.

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