Key Takeaways & Executive Findings
- •• • Ultrahigh sensitivity of 248.41 kPa−1 over a broad pressure range (0–19 kPa), enabling detection of subtle physiological signals with high fidelity. • • High gauge factor of 34.4, indicating exceptional piezoresistive response for precise strain quantification. • • Fast response (24 ms) and recovery (69 ms) times, suitable for real-time monitoring of dynamic motions. • • Stable operation over 5000 loading–unloading cycles, demonstrating mechanical robustness and long-term durability for wearable applications.
Abstract
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.
1. Introduction
Conventional flexible pressure sensors rely on synthetic polymers and metal-based materials, which incur high processing costs and pose environmental hazards upon disposal. Biomass-derived carbon aerogels, particularly those from cellulose nanofibers, offer a sustainable alternative due to their high surface area and tunable porosity. However, their intrinsic brittleness and tendency to structural collapse under cyclic loading have severely limited their practical application in wearable sensing. The challenge lies in simultaneously achieving high sensitivity, mechanical strength, and long-term stability—a triad that has remained elusive in existing aerogel-based sensors.
This work addresses this bottleneck by employing bidirectional freezing to reorganize cellulose nanofibers, nitrogen-doped carbon nanosheets, and tetrapod ZnO whiskers into a mechanically stable, parallel lamellar architecture. The incorporation of T-ZnOWs as rigid interlayer pillars creates a 'layer-support' structure that not only enhances stress transfer but also introduces localized high-stress regions due to modulus mismatch, amplifying the piezoresistive response. This structural engineering approach, combined with PDMS encapsulation, yields a sensor with exceptional sensitivity (248.41 kPa−1), high gauge factor (34.4), and robust cycling stability (5000 cycles), marking a significant advancement in biomass-derived carbon aerogel sensors for wearable and intelligent applications.
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Wang Yichen, Suo Fang, Ben Yihang, Guo Rui, Yao Yongtao, Liu Zhenbo (2026). A Bidirectionally Frozen Carbon Aerogel Reinforced by Tetrapod ZnO Bridges for High-Performance Pressure Sensing. New Carbon Materials. https://doi.org/10.1016/S1872-5805(26)61103-1
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Frequently Asked Questions
What is the failure mechanism of the aerogel under repeated loading, and how does the 'layer-support' structure mitigate it?
The aerogel's brittleness and interlayer slippage are primary failure modes. The T-ZnOWs act as rigid pillars that bridge adjacent carbon layers, preventing slippage and distributing stress uniformly. This suppresses structural collapse, enabling stable operation over 5000 cycles without significant degradation.
How does the incorporation of nitrogen-doped carbon nanosheets contribute to the sensing performance?
Nitrogen doping introduces defect-rich conductive paths, which enhance the piezoresistive response by increasing the sensitivity of electrical resistance to mechanical deformation. This is reflected in the ultrahigh sensitivity of 248.41 kPa−1 and gauge factor of 34.4.
What is the role of PDMS infiltration in the sensor's durability and performance?
PDMS infiltration forms a conformal elastic encapsulating layer that protects the aerogel from environmental degradation and mechanical wear, while maintaining flexibility. This contributes to the sensor's long-term stability over 5000 cycles and fast response/recovery times.
How does the bidirectional freezing technique influence the final structure and sensing properties?
Bidirectional freezing aligns the components into parallel lamellae, creating a well-ordered 'layer-support' structure. This alignment enhances directional stress transfer and cooperative deformation, leading to higher sensitivity and mechanical robustness compared to randomly distributed structures.
What are the potential scalability and cost implications of this fabrication method for commercial wearable sensors?
The use of abundant cellulose and relatively simple freezing and infiltration processes suggests potential for scalable production. However, the need for precise control of freezing conditions and the cost of T-ZnOWs may impact cost-effectiveness. Further optimization is required to achieve cost parity with existing commercial sensors.
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