Abstract

Significance A critical obstacle of flexible electronics for chronic implants is the absence of thin-film barriers to biofluids with multidecade lifetimes. Previously explored materials are unsuitable due to limitations of ( i ) extrinsic factors, such as the practical inability to avoid localized defects, and/or ( ii ) intrinsic properties, such as finite water permeability. The work presented here overcomes these challenges by combining pristine thermal SiO 2 layers with processing steps for their integration onto flexible electronics. Experimental and theoretical studies reveal the key aspects of this material system. Accelerated immersion tests and cyclic bending measurements suggest robust, defect-free operation with various electronic components and an integrated system for multiplexed mapping of electrophysiological signals. The findings have broad relevance to diverse biointegrated electronics and optoelectronics.