Geometric topology–driven purely resistive electrodes in hexagonally close-packed urchin-like hollow carbon sphere monolayers for flexible electronics

Abstract

Periodic array–structured carbon materials have attracted considerable attention owing to their broad applications in heterogeneous catalysis, energy storage, photonics and sensors. However, they are typically assembled into multi-layer stacks that introduce complex internal interfaces, leading to carrier scattering and charge accumulation, thereby reducing electrical performance. Furthermore, structural changes under external force limit the applicability of multi-layer materials in flexible electronics. Herein, to effectively address these issues, a carbon microsphere film with geometric-topological design is introduced. A monolayer colloidal microsphere template is first prepared by the self-assembly technique, and the subsequent in situ growth yields an urchin-like hollow carbon sphere array film. It exhibits a stable 0° phase angle over a wide frequency range (1 Hz–0.1 MHz) and demonstrates excellent linearity and symmetry in current–voltage behaviour, with no hysteresis of the electrical signal. It exhibits pure resistance behaviour and precision with variations of <0.025 %. When made into a flexible pressure sensor, the sensor achieves a sensitivity of ≤408 kPa⁻¹ and an ultrafast response time of 0.8 ms. In addition, it can enable individuals with limited experience to perform precise manual operations such as vein injection.