Biaxially Stretchable Ultrathin Si Enabled by Serpentine Structures on Prestrained Elastomers

Building stretchable electronics from inorganic materials is a testified pathway toward devices with high performances for many applications in fields such as optoelectronics, biomedical, etc. Owing to the unstretchable nature of these materials (e.g., brittleness of Si), existing ways to enable stretchabilities mainly involve either bonding thin films on a prestrained elastomer substrate or configuring materials into thin serpentine layouts. It is hypothesized that a combination of prestrain and serpentine will lead to advantages in the: (1) enlarged stretchability at the materials and (2) enhanced areal fill factor of the materials, when compared with existing serpentine structures without using prestrain strategy. This paper reports a biaxially stretchable Si structure and its optoelectronic devices enabled through the combination of serpentine structure designs and prestrain strategy on an elastomer substrate. The detailed device design and fabrication, mechanical analysis, and electrical performance characterization illustrate the key concept and validate the hypothesis. The Si nanomesh can be stretched by 75% biaxially with prestrain of 50% and has an enhanced areal fill factor of 125%. The combined strategy of prestrain and serpentine is applicable to a wide range of materials and devices, and the demonstrated results can be useful for stretchable electronics, optoelectronics, and many others.