Freestanding Serpentine Silicon Strips with Ultrahigh Stretchability over 300% for Wearable Electronics

Abstract Well‐functionalized electronic materials, such as silicon, in a stretchable format are desirable for high‐performance wearable electronics. However, obtaining Si materials that meet the required stretchability of over 100% for wearable applications remains a significant challenge. Herein, a rational design strategy is proposed to achieve freestanding serpentine Si strips (FS‐Si strips) with ultrahigh stretchability, fulfilling wearable requirements. The self‐supporting feature makes the strips get rid of excessive constraints from substrates and enables them to deform with the minimum strain energy. Micrometer‐scale thicknesses enhance robustness, and large diameter‐to‐width ratios effectively reduce strain concentration. Consequently, the FS‐Si strips with the optimum design could withstand 300% stretch, bending, and torsion without fracturing, even under rough manual operation. They also exhibit excellent stability and durability over 50,000 cycles of 100% stretching cycles. For wearable applications, the FS‐Si strips can maintain conformal contact with the skin and have a maximum stretchability of 120%. Moreover, they are electrically insensitive to large deformations, which ensure signal stability during their daily use. Combined with mature processing techniques and the excellent semiconductor properties of Si, FS‐Si strips are promising core stretchable electronic materials for wearable electronics.