Flexible, ultra-low dielectric polyimide aerogels prepared via 10-minute ambient pressure blow-drying for high-gain Sub-6 GHz patch antenna

Abstract

Conventional rigid patch antennas, constrained by high-permittivity substrates (ε_r > 3.0) with severe dielectric loss (tanδ > 0.02), suffer from catastrophic performance degradation at elevated frequencies (>3 GHz) and inherent inflexibility that fundamentally prohibits their integration in wearable electronics. This work presents a breakthrough in synthesizing PMMA-reinforced polyimide aerogels (PIAs) via a 10-min ambient pressure drying (APD) strategy, enabling tunable porosity (>90%) and ultra-low dielectric constants (ε_r = 1.35, tanδ < 0.01). The incorporation of PMMA into the PI matrix endows the aerogel skeleton with outstanding mechanical resilience (tensile strength of 7.2 MPa and fracture energy of 45.8 kJ/m²), while effectively suppressing capillary-induced shrinkage to below 2.1% during solvent evaporation. The synergistic interplay between PMMA encapsulation and APD-optimized solvent exchange yields a hierarchical nanoporous structure (30 nm average pore size) with exceptional thermal insulation (0.036 W/m·K). When deployed as a substrate for flexible Sub-6 GHz patch antennas, the aerogel exhibits 106% gain enhancement (9.92 dBi) and broad impedance bandwidth (3.862–3.941 GHz), outperforming conventional FR-4 substrates. This work establishes a scalable, low-cost paradigm for multifunctional aerogels in wearable electronics and high-frequency communication systems.