Ultrathin, High Capacitance Capping Layers for Silicon Electronics with Conductive Interconnects in Flexible, Long‐Lived Bioimplants

Abstract

Bioimplants that incorporate active electronic components at the tissue interface rely critically on materials that are biocompatible, impermeable to biofluids, and capable of intimate electrical coupling for high‐quality, chronically stable operation in vivo. This study reports a materials strategy that combines silicon nanomembranes, thermally grown layers of SiO2 and ultrathin capping structures in materials with high dielectric constants as the basis for flexible and implantable electronics with high performance capabilities in electrophysiological mapping. Accelerated soak tests at elevated temperatures and results of theoretical modeling indicate that appropriately designed capping layers can effectively limit biofluid penetration and dramatically extend the lifetimes of the underlying electronic materials when immersed in simulated biofluids. Demonstration of these approaches with actively multiplexed, amplified systems that incorporate more than 100 transistors in thin, flexible platforms highlights the key capabilities and the favorable scaling properties. These results offer an effective encapsulation approach for long‐lived bioelectronic systems with broad potential for applications in biomedical research and clinical practice.

Ultra‐Thin Flexible Encapsulating Materials for Soft Bio‐Integrated Electronics

“…The chronic bioencapsulation layers are manufactured by integrating combinations of organic or inorganic materials with various deposition temperatures, thicknesses, and techniques such as spin‐coating, dip‐coating, chemical vapor deposition (CVD), or physical vapor deposition (PVD). [ 16 , 239 , 240 , 241 , 242 , 243 , 244 ] Among the various materials, polymer layers (SU‐8, PDMS, Parylene C, etc.) can serve as long‐term bio‐encapsulations, formed comparatively simply and at low cost, but the layers need to be quite thick, ranging from tens to hundreds of microns because of the polymers’ high value of water vapor transmission rates (WVTRs).…”

Ultraflexible and Stretchable Intrafascicular Peripheral Nerve Recording Device with Axon‐Dimension, Cuff‐Less Microneedle Electrode Array

“…Compared with other common dielectric coating approaches where a thin layer of organic or inorganic insulator was deposited via vapor deposition, high-quality silicon dioxide formed using thermal oxidation was shown to have good biocompatibility and longevity in the physiological environment. [33][34][35][36][37] This is the first instance of thermal oxide grown on microneedles, to our knowledge. The 70 µm thick PDMS as the substrate material enhanced the flexibility of the device and enabled the electrode array to conformally attach to the small diameter autonomic nerve.…”

Ultra-flexible and Stretchable Intrafascicular Peripheral Nerve Recording Device with Axon-dimension, Cuff-less Microneedle Electrode Array

“…Compared with other common dielectric coating approaches where a thin layer of organic or inorganic insulator was deposited via vapor deposition, high-quality silicon dioxide formed using thermal oxidation was shown to have good biocompatibility and longevity in the physiological environment [30][31][32][33][34] . This is the first instance of thermal oxide grown on microneedles, to our knowledge.…”