Biocompatible hybrid flip chip microsystem integration for next generation wireless neural interfaces

Topper, Michael J.; Klein, M.; Buschick, K.; Glaw, V.; Orth, K.; Ehrmann, O.; Hütter, Matthias; Oppermann, Hermann; Becker, K.-F.; Braun, T.; Ebling, F.; Reichl, H.; Kim, S.; Tathireddy, Prashant; Chakravarty, S.; Solzbacher, F.

doi:10.1109/ectc.2006.1645734

Cited by 22 publications

(11 citation statements)

References 3 publications

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“…(1)(2)(3)(4)(5)(6)(7) Among the Parylene variants, Parylene-N and -C are currently approved by the Food and Drug Administration (FDA) as class VI polymers, allowing them to be used in biomedical devices. (8) A fully integrated, wireless neural interface device is being developed to restore functions to patients with neurological disorders, (9) and Parylene-C was studied as a conformal, hermetic, and biocompatible encapsulation layer for the device. (10) In this work, we studied variables that affect the application of Parylene-C to the neural interface device.…”

Section: Introductionmentioning

confidence: 99%

Effect of Thermal and Deposition Processes on Surface Morphology, Crystallinity, and Adhesion of Parylene-C

Hsu

Rieth

Kammer

et al. 2008

Sensors and Materials

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Neural interface devices have been developed for neural science and neuroprosthetics applications to record and stimulate neural signals. Chemical-vapor-deposited Parylene-C films were studied as an encapsulation material for such an implantable device. The surface morphology of an implant affects its biocompatibility; thus, the Parylene-C surface morphology was investigated as a function of the precursor sublimation rate by atomic force microscopy. We found that high precursor sublimation rates resulted in slightly higher root-mean-square surface roughnesses (from 5.78 to 9.53 nm for deposition rates from 0.015 to 0.08 g/min). The crystallinity affects the physical properties of semicrystalline polymers, and various heat treatments were found to modify the crystallinity of Parylene-C films, as assessed by X-ray diffraction (XRD). The XRD peak at 2θ = ~14.5° increased in intensity and decreased in full width at half maximum with increasing annealing temperature, indicating an increase in film crystallinity. Poor adhesion would compromise the protection offered by Parylene-C coatings. The adhesion between Parylene-C and silicon, amorphous silicon carbide, and boron silicate glass substrates were evaluated using the standard tape adhesion test from the American Society for Testing and Materials (ASTM) in an attempt to minimize the occurrence of delamination failures. The tape adhesion tests indicated strong adhesion for all the as-deposited Parylene films with the application of an adhesion promoter (Silquest A-174 ® silane). However, annealing the deposited films at temperatures from 85 to 150°C in air for 20 min reduced film adhesion, and also the adhesion testing procedure used significantly affects the results obtained. Supporting evidence suggested that the thermal stress generated in the films weakened the adhesive force. We concluded that 88 Sensors and Materials, Vol. 20, No. 2 (2008) the Parylene-C film properties (surface morphology, crystallinity, and adhesion) changed during deposition and thermal annealing, suggesting that the Parylene-C film properties can be tailored and that, with care, failure due to film delamination can be avoided.

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Section: Introductionmentioning

confidence: 99%

Effect of Thermal and Deposition Processes on Surface Morphology, Crystallinity, and Adhesion of Parylene-C

Hsu

Rieth

Kammer

et al. 2008

Sensors and Materials

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“…7a) [1]. This integration concept uses the UEA as a "circuit board", where the interconnections between components are made through a thin film metal stack which is sputter-deposited on the backside of the UEA (Fig.…”

Section: System Integration and Assemblymentioning

confidence: 99%

“…The Integrated Neural Interface (INI) under development can utilize either a Utah Electrode Array (UEA) or Utah Slanted Electrode Array (USEA) to make contact with neural tissue. These MEMS devices typically consist of 10×10 arrays with an electrode-to-electrode spacing of 400 µm and electrode lengths between 0.5 and 1.5 mm [1].…”

Section: Introductionmentioning

confidence: 99%

A wireless neural interface for chronic recording

Harrison

Kier

Kim

et al. 2008

2008 IEEE Biomedical Circuits and Systems Conference

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Abstract-A primary goal of the Integrated Neural Interface Project (INIP) is to develop a wireless, implantable device capable of recording neural activity from 100 micromachined electrodes. The heart of this recording system is a low-power integrated circuit that amplifies 100 weak neural signals, detects spikes with programmable threshold-crossing circuits, and returns these data via digital radio telemetry. The chip receives power, clock, and command signals through a coil-to-coil inductive link. Here we report that the isolated integrated circuit successfully recorded and wirelessly transmitted digitized electrical activity from peripheral nerve and cortex at 15.7 kS/s. The chip also simultaneously performed accurate on-chip spike detection and wirelessly transmitted the spike threshold-crossing data. We also present preliminary successful results from full system integration and packaging.

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“…1(b) [15], which amplifies detected neural signals, processes and transmits them to an extracorporeal receiver. Since the integrated UEA/IC system [14] dissipates a certain amount of power during operation, it will increase the temperature in surrounding tissues where it is implanted.…”

Section: Introductionmentioning

confidence: 99%

In vitro and in vivo study of temperature increases in the brain due to a neural implant

Kim

Tathireddy

Normann

et al. 2007

2007 3rd International IEEE/EMBS Conference on Neural Engineering

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A chronically implantable, wireless neural interface device requires integrating electronic circuitry with the interfacing microelectrodes in order to eliminate wired connections. Since the integrated circuit (IC) dissipates a certain amount of power, it will raise the temperature in surrounding tissues where it is implanted. In this paper, the thermal influence of the integrated 3-dimensional Utah Electrode Array (UEA) device implanted in the brain was investigated by experimental measurement in vitro as well as in vivo. The maximum temperature increase due to the integrated UEA system was measured to be 0.067 °C/mW for in vitro and 0.050 °C/mW for in vivo conditions. Lower temperature increases of in vivo measurement are due to convection through the blood perfusion presenting in the living tissues.

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Biocompatible hybrid flip chip microsystem integration for next generation wireless neural interfaces

Cited by 22 publications

References 3 publications

Effect of Thermal and Deposition Processes on Surface Morphology, Crystallinity, and Adhesion of Parylene-C

Effect of Thermal and Deposition Processes on Surface Morphology, Crystallinity, and Adhesion of Parylene-C

A wireless neural interface for chronic recording

In vitro and in vivo study of temperature increases in the brain due to a neural implant

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