Highly Stretchable Thermally-Grown Silicon Dioxide with Wavy Structures Encapsulation for Biomedical Applications

Flexible and stretchable bioelectronic devices that can be applied to targets such as heart and liver where repetitive deformation occurs are currently being actively investigated as next-generation devices. These organic material-based electronic devices require an encapsulation layer for long-term stability. Therefore, the development of mechanically stretchable and highly impermeable encapsulating materials is required to develop stretchable bioelectronic devices.<br/>In this research, we developed the highly stretchable and impermeable encapsulations by applying a wavy-structure to the thermally-grown SiO₂. A thermally-grown SiO₂, oxidized from single-crystalline silicon wafer at high temperature, has an extremely low water vapor transmission rate (WVTR) due to amorphous structure and high density with low defects. In addition, we effectively implemented high stretchability through wavy-structure design, overcoming the intrinsically low elastic deformation limit of SiO₂. The stretchability and barrier properties were carried out by uniaxial tensile test and electrical Ca test. By theoretically analyzing the mechanical behavior of wavy-structured SiO₂, the universal deformation model and correlation between stretchability and characteristic of wavy structure were carried out. This stretchable encapsulation shows 20.1% of uniaxial stretchability and 1.11 x 10^-6 g m^-2 day^-1 of WVTR, simultaneously. Moreover, it demonstrates highly reliable barrier properties even after 1,000 stretching cycles at 90% of their stretchability. Therefore, the developed wavy-structured thermally grown SiO₂ is suitable to protect stretchable organic-based bioelectronic devices.