Transferred, Ultrathin Oxide Bilayers as Biofluid Barriers for Flexible Electronic Implants

Enming Song, Yoon Kyeung Lee, Rui Li, Jinghua Li, Xin Jin, Ki Jun Yu, Zhaoqian Xie, Hui Fang, Yiding Zhong, Haina Du, Jize Zhang, Guanhua Fang, Yerim Kim, Younghee Yoon, Muhammad A. Alam, Yongfeng Mei, Yonggang Huang, John A. Rogers*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

53 Scopus citations


The work presented here introduces a materials strategy that involves physically transferred, ultrathin layers of silicon dioxide (SiO2) thermally grown on silicon wafers and then coated with hafnium oxide (HfO2) by atomic layer deposition, as barriers that satisfy requirements for even the most challenging flexible electronic devices. Materials and physics aspects of hydrolysis and ionic transport associated with such bilayers define their performance and reliability characteristics. Systematic experimental studies and reactive diffusion modeling suggest that the HfO2 film, even with some density of pinholes, slows dissolution of the underlying SiO2 by orders of magnitude, independent of the concentration of ions in the surrounding biofluids. Accelerated tests that involve immersion in phosphate-buffered saline solution at a pH of 7.4 and under a constant electrical bias demonstrate that this bilayer barrier can also obstruct the transport of ions that would otherwise cause drifts in the operation of the electronics. Theoretical drift–diffusion modeling defines the coupling of dissolution and ion diffusion, including their effects on device lifetime. Demonstrations of such barriers with passive and active components in thin, flexible electronic test structures highlight the potential advantages for wide applications in chronic biointegrated devices.

Original languageEnglish (US)
Article number1702284
JournalAdvanced Functional Materials
Issue number12
StatePublished - Mar 21 2018


  • biofluids
  • hafnium oxide
  • hermetic packaging
  • silicon dioxide
  • water-and-ion barriers

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • General Chemistry
  • Condensed Matter Physics
  • General Materials Science
  • Electrochemistry
  • Biomaterials


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