Wet-etching fabrication of flexible and transparent silicon frameworks for imperceptible wearable electronics

Electronic materials with mechanical flexibility and visual transparency are highly desirable for imperceptible wearable electronics that can alleviate wearing reluctance. However, as a multifunctional sensing material in modern electronics, silicon is typically rigid and opaque, limiting its applications in imperceptible wearable electronics. Here, a novel strategy is proposed to fabricate single-crystalline silicon frameworks (sc-SiFs) through alkali etching. The as-prepared sc-SiFs exhibit a minimum bending radius of 6 mm and a light transmittance of up to 77%. The remarkable performance results from the unique framework structures, which provide adequate space for stress relief and light transmission. By precisely controlling the structural parameters, the mechanical and optical properties of SiFs can be easily tailored to meet the diverse requirements of various applications. Despite new properties, sc-SiFs preserve the electronic properties of silicon, which makes them good candidates for wearable electronics. As an example, imperceptible bending sensors based on sc-SiFs have been constructed to detect physiological activities, including facial expressions and swallowing. This work provides a scalable method for fabricating flexible and transparent silicon materials, which will facilitate the development of imperceptible wearable electronics. This work proposes a method of low-cost alkali etching to fabricate single-crystalline silicon frameworks, which will promote the research and application of silicon-based imperceptible wearable electronics.