Engineering Route for Stretchable, 3D Microarchitectures of Wide Bandgap Semiconductors for Biomedical Applications

Abstract

Wide bandgap (WBG) semiconductors have attracted significant research interest for the development of a broad range of flexible electronic applications, including wearable sensors, soft logical circuits, and long‐term implanted neuromodulators. Conventionally, these materials are grown on standard silicon substrates, and then transferred onto soft polymers using mechanical stamping processes. This technique can retain the excellent electrical properties of wide bandgap materials after transfer and enables flexibility; however, most devices are constrained by 2D configurations that exhibit limited mechanical stretchability and morphologies compared with 3D biological systems. Herein, a stamping‐free micromachining process is presented to realize, for the first time, 3D flexible and stretchable wide bandgap electronics. The approach applies photolithography on both sides of free‐standing nanomembranes, which enables the formation of flexible architectures directly on standard silicon wafers to tailor the optical transparency and mechanical properties of the material. Subsequent detachment of the flexible devices from the support substrate and controlled mechanical buckling transforms the 2D precursors of wide band gap semiconductors into complex 3D mesoscale structures. The ability to fabricate wide band gap materials with 3D architectures that offer device‐level stretchability combined with their multi‐modal sensing capability will greatly facilitate the establishment of advanced 3D bio‐electronics interfaces.

Convergence of Implantable Bioelectronics and Brain–Computer Interfaces

“…By using photolithography on both sides of free-standing nanomembranes, the method creates flexible structures on commercial silicon wafers, allowing for the customization of the material's optical transparency and mechanical properties. 131 Bose et al developed a retrievable implant for therapeutic xenogeneic cells, which can work for over 130 days (Figure 5G). 132 Garcia-Cortadella et al implanted a graphene active sensor array for mapping of a wide frequency band and epicortical brain signal.…”

“…Truong et al developed a stamping-free micromachining process for 3D flexible and stretchable wide bandgap electronics. By using photolithography on both sides of free-standing nanomembranes, the method creates flexible structures on commercial silicon wafers, allowing for the customization of the material’s optical transparency and mechanical properties . Bose et al developed a retrievable implant for therapeutic xenogeneic cells, which can work for over 130 days (Figure G) .…”

Novel fabrication techniques for ultra-thin silicon based flexible electronics

“…Recent advancements have enhanced the durability and reliability of Si while reducing rigidity. These properties can be improved through the implementation of unique structural designs, such as serpentine or wavy structures (figure 2(c)) [120][121][122][123][124], and the protection of the device from external environmental factors and mechanical deformation through encapsulation methods [125][126][127][128][129]. Another challenge is the need to maintain low temperatures during the Si fabrication process in flexible electronics.…”