A Three-Dimensional 64-Site Folded Electrode Array Using Planar Fabrication

Abstract

Neuroscience and neuroprosthetic devices are increasingly in need of more compact less invasive 3-D electrode arrays for interfacing with neural tissue. To meet these needs, a folding 64-site 3-D array architecture has been developed. The microstructure, in which four probes and two platforms are fabricated as a single planar unit, results in a low-profile <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(&lt; 350\hbox{-}\mu\hbox{m})$</tex></formula> narrow-platform (0.604- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{mm}^{2}$</tex></formula> silicon footprint) implant for cortical use. Signals are routed from 177- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}^{2}$</tex></formula> iridium sites through polysilicon lines to the probe back end and then across 4- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ \mu\hbox{m}$</tex></formula> -thick parylene-encased electroplated-gold folding lead transfers to the associated platform. Three levels of interconnect with a 10- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> minimum pitch are utilized for the 32 leads that traverse the platforms. After rapid microassembly, micromachined latches are used to fasten the folded device. Two flexible parylene cables with gold leads at a 20- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> pitch are monolithically integrated with the probes to minimize tethering and avoid any need for lead bonding within the array, and these cables carry the neural signals to a remote circuit module or percutaneous connector. With thin <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(\sim\! \! 15\hbox{-}\mu\hbox{m})$</tex></formula> boron-doped shanks at a <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim\!\! 200 \hbox{-}\mu\hbox{m}$</tex></formula> pitch, the array displaces only 1.7% of the 0.64- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\hbox{mm}^{2}$</tex></formula> instrumented tissue area, assuming a 100- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ \mu\hbox{m}$</tex></formula> recording range. Neural signals were recorded in vivo from the guinea pig auditory cortex. <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hfill$</tex></formula> [2010-0200]