A Bidirectionally Frozen Carbon Aerogel Reinforced by Tetrapod ZnO Bridges for High-Performance Pressure Sensing
Flexible pressure sensors that simultaneously achieve high sensitivity, mechanical strength, and long-term stability remain challenging, particularly for biomass-derived carbon aerogels that are intrinsically brittle and prone to structural collapse. Here, we report a bidirectionally frozen carbon aerogel reinforced with tetrapod ZnO whiskers (T-ZnOWs) for high-performance pressure sensing. The aerogel is composed of cellulose nanofibers (CNFs), nitrogen-doped carbon nanosheets (NCs), and T-ZnOWs, which are reorganized into a mechanically stable, parallel lamellar structure via bidirectional freezing. T-ZnOWs act as rigid interlayer pillars, bridging adjacent carbon lamellae to form a 'layer-support' structure that enables efficient directional stress transfer, suppresses interlayer slippage, and promotes cooperative deformation. The nitrogen-doped carbon nanosheets introduce defect-rich conductive paths, enhancing piezoresistive response. Due to modulus mismatch between the supports and carbon layers, applied stress concentrates at layer/support interfaces, generating localized high-stress regions that amplify electrical signal changes. The aerogel is infiltrated with polydimethylsiloxane (PDMS) to form a conformal elastic encapsulating layer, improving durability. The resulting sensor exhibits a high gauge factor of 34.4, an ultrahigh sensitivity of 248.41 kPa−1 over a broad pressure range (0–19 kPa), fast response (24 ms) and recovery (69 ms) times, and stable operation over 5000 loading–unloading cycles. The sensor reliably detects physiological signals and joint motions, demonstrating potential for wearable and intelligent sensing applications. This work provides a strategy to improve the mechanical reliability and sensing performance of biomass-derived carbon aerogels.