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A 16-Channel Wireless Neural Recording System-on-Chip with CHT Feature Extraction Processor in 65nm CMOS

Cosimo Aprile, Volkan Cevher, Catherine Dehollain, Florian Dylan Fallegger, Stéphanie Lacour, Yusuf Leblebici, Alix Esther Anne Trouillet, Kerim Türe, Arda Uran

Wireless implantable neural recording chips enable multichannel data acquisition with high spatiotemporal resolution in situ. Recently, the use of machine learning approaches on neural data for diagnosis and prosthesis control have renewed the interest in this field, and increased even more the demand for multichannel data. However, simultaneous data acquisition from many channels is a grand challenge due to data rate and power limitations on wireless transmission for implants. As a result, recent studies have focused on on-chip classifiers (Fig. 1 top), despite the fact that only primitive classifiers can be placed on resource-constrained chips. Moreover, robustness of the chosen algorithm cannot be guaranteed pre-implantation due to the scarcity of patient-specific data; waveforms can change over time due to electrode micro migration or tissue reaction, highlighting the need for robust adaptive features.

2021

Viscoelastic surface electrode arrays to interface with viscoelastic tissues

Florian Dylan Fallegger, Stéphanie Lacour, Christina Myra Tringides, Alix Esther Anne Trouillet, Nicolas Vachicouras, Hao Wang

Bioelectronic interfacing with living tissues should match the biomechanical properties of biological materials to reduce damage to the tissues. Here, the authors present a fully viscoelastic microelectrode array composed of an alginate matrix and carbon-based nanomaterials encapsulated in a viscoelastic hydrogel for electrical stimulation and signal recording of heart and brain activities in vivo. Living tissues are non-linearly elastic materials that exhibit viscoelasticity and plasticity. Man-made, implantable bioelectronic arrays mainly rely on rigid or elastic encapsulation materials and stiff films of ductile metals that can be manipulated with microscopic precision to offer reliable electrical properties. In this study, we have engineered a surface microelectrode array that replaces the traditional encapsulation and conductive components with viscoelastic materials. Our array overcomes previous limitations in matching the stiffness and relaxation behaviour of soft biological tissues by using hydrogels as the outer layers. We have introduced a hydrogel-based conductor made from an ionically conductive alginate matrix enhanced with carbon nanomaterials, which provide electrical percolation even at low loading fractions. Our combination of conducting and insulating viscoelastic materials, with top-down manufacturing, allows for the fabrication of electrode arrays compatible with standard electrophysiology platforms. Our arrays intimately conform to the convoluted surface of the heart or brain cortex and offer promising bioengineering applications for recording and stimulation.

NATURE RESEARCH2021