Hierarchical Graphene Nanowall Nanomesh Enables Confinement-Enhanced Gas Sensing for Wearable Applications

Abstract

Wearable gas sensors are essential for real-time monitoring of personal exposure, yet achieving high sensitivity at room temperature while maintaining mechanical compliance remains a significant challenge. Here, we report a hierarchical graphene nanowall (GNW) nanomesh that integrates material-specific transport characteristics with a three-dimensional (3D) porous architecture for enhanced gas-sensing performance. The GNW nanomesh is realized by directly growing vertically oriented graphene nanowalls on a flexible polymer nanomesh using a low-temperature plasma-enhanced chemical vapor deposition process enabled by a thermally robust parylene-coated polyimide substrate. The resulting 3D-on-3D architecture provides high accessibility of active sites and mechanically compliant pathways suitable for wearable applications. Compared to planar GNWs, the hierarchical nanomesh exhibits a sixfold enhancement in sensitivity and faster response under room-temperature operation. Particle-based simulations suggest that confined geometries within GNWs promote localized molecular trajectories and increased collision events, consistent with the observed performance enhancement. Integration into a wearable smart mask further demonstrates stable real-time detection of NO₂ over extended operation. This work highlights that combining intrinsic material transport characteristics with hierarchical nanoarchitectural design offers an effective strategy for advancing wearable gas sensing beyond conventional surface-area-driven approaches.

Graphical Abstract

Keywords

Graphene nanowall nanomesh / Hierarchical nanoarchitecture / Gas sensing / Wearable sensors / Confinement effects / Molecular transport

References

[1] Zhu X, Wu K, Xie X, Anderson SW, Zhang X. A robust near-field body area network based on coaxially-shielded textile metamaterial. Nat Commun, 2024, 15: 6589

[2] Nguyen DT, Zeng Q, Tian X, Chia P, Wu C, Liu Y, Ho J. Ambient health sensing on passive surfaces using metamaterials. Sci Adv, 2024, 10: eadj6613

[3] Zhou Z, He X, Xiao J, Pan J, Li M, Xu T, Zhang X. Machine learning-powered wearable interface for distinguishable and predictable sweat sensing. Biosens Bioelectron, 2024, 265 ArticleID: 116712

[4] Che Z, Wan X, Xu J, Duan C, Zheng T, Chen J. Speaking without vocal folds using a machine-learning-assisted wearable sensing-actuation system. Nat Commun, 2024, 15: 1873

[5] Wang J, Fatima-Ezzahra E, Dai J, Liu Y, Pei C, Li H, Wang Z, Huang X. Ligand-assisted deposition of ultra-small Au nanodots on Fe 2 O 3/reduced graphene oxide for flexible gas sensors. Nanoscale Adv, 2022, 4: 1345

[6] Quan W, Shi J, Luo H, Fan C, Lv W, Chen X, Zeng M, Yang J, Hu N, Su Y, Wei H, Yang Z. Fully flexible MXene-based gas sensor on paper for highly sensitive room-temperature nitrogen dioxide detection. ACS Sens, 2023, 8: 103

[7] Yang W, Huo Y, Wang T, Liu X, Li D, Yu H, Dong X, Yang Y. RGO@In2O3 based flexible gas sensor: efficient monitoring of trace NO2 gas at room temperature. Sens Actuators B Chem, 2025, 430 ArticleID: 137359

[8] Yang Z, Liu Y, Chen M, Xiang M, Gao G, Cui D, Li Q. A breathable, waterproof and battery-free wearable e-nose with high flexibility based on MEMS gas sensors for accurate identification of volatile aromatic hydrocarbons. Appl Mater Today, 2025, 42 ArticleID: 102527

[9] Dong H, Li X, Liu Y, Cheng W, Han C, Yin Y, Li X, Shao C, Liu Y. Wearable, breathable, and wireless gas sensor enables highly selective exhaled ammonia detection and real-time noninvasive illness diagnosis. ACS Sens, 2025, 10: 3964

[10] Ansari HR, Mirzaei A, Shokrollahi H, Kumar R, Kim J-Y, Kim HW, Kumar M, Kim. Flexible/wearable resistive gas sensors based on 2D materials. J Mater Chem C, 2023, 11: 6528

[11] Zhu S, Tang Y, Lin C, Liu XY, Lin Y. Recent advances in patterning natural polymers: from nanofabrication techniques to applications. Small Methods, 2021, 5: 2001060

[12] Chowdhury N, Bhowmik BJNA. Micro/nanostructured gas sensors: the physics behind the nanostructure growth, sensing and selectivity mechanisms. Nanoscale Adv, 2021, 3: 73

[13] Maciulis V, Ramanaviciene A, Plikusiene IJ. Recent advances in synthesis and application of metal oxide nanostructures in chemical sensors and biosensors. Nanomaterials (Basel), 2022, 12 ArticleID: 4413

[14] Zhou T, Zhang T. Recent progress of nanostructured sensing materials from 0D to 3D: overview of structure–property-application relationship for gas sensors. Small Methods, 2021, 5: 2100515

[15] Kong M, Yang M, Li R, Long Y-Z, Zhang J, Huang X, Cui X, Zhang Y, Said Z, Li C. Graphene-based flexible wearable sensors: mechanisms, challenges, and future directions. Int J Adv Manuf Technol, 2024, 131: 3205

[16] Zhang H, He R, Niu Y, Han F, Li J, Zhang X, Xu F. Graphene-enabled wearable sensors for healthcare monitoring. Biosens Bioelectron, 2022, 197: 113777

[17] Huang C, Hao Z, Wang Z, Wang H, Zhao X, Pan Y. An ultraflexible and transparent graphene-based wearable sensor for biofluid biomarkers detection. Adv Mater Technol, 2022, 7: 2101131

[18] Raza T, Tufail MK, Ali A, Boakye A, Qi X, Ma Y, Ali A, Qu L, Tian M. Wearable and flexible multifunctional sensor based on laser-induced graphene for the sports monitoring system. ACS Appl Mater Interfaces, 2022, 14: 54170

[19] Chen Y, Li G, Mu W, Wan X, Lu D, Gao J, Wen D. Nonenzymatic sweat wearable uric acid sensor based on N-doped reduced graphene oxide/Au dual aerogels. Anal Chem, 2023, 95: 3864

[20] Na HR, Lee HJ, Jeon JH, Kim H-J, Jerng S-K, Roy SB, Chun S-H, Lee S, Yun Y. Vertical graphene on flexible substrate, overcoming limits of crack-based resistive strain sensors. npj Flex Electron, 2022, 6: 2

[21] Abolpour Moshizi S, Azadi S, Belford A, Razmjou A, Wu S, Han ZJ, Asadnia M. Development of an ultra-sensitive and flexible piezoresistive flow sensor using vertical graphene nanosheets. Nano-Micro Lett, 2020, 12: 109

[22] Bo Z, Yuan M, Mao S, Chen X, Yan J, Cen K, Chemical A. Decoration of vertical graphene with tin dioxide nanoparticles for highly sensitive room temperature formaldehyde sensing. Sens Actuators B: Chem, 2018, 256: 1011

[23] Wang Q, Liu Q, Zhong G, Xu T, Zhang XJAC. Wearable vertical graphene-based microneedle biosensor for real-time ketogenic diet management. Anal Chem, 2024, 96: 8713

[24] Zheng W, Zhao X, Fu W. Review of vertical graphene and its applications. ACS Appl Mater Interfaces, 2021, 13: 9561

[25] Wu J, Li Z, Xie X, Tao K, Liu C, Khor KA, Miao J, Norford LK. 3D superhydrophobic reduced graphene oxide for activated NO2 sensing with enhanced immunity to humidity. J Mater Chem A, 2018, 6: 478

[26] Wu J, Feng S, Wei X, Shen J, Lu W, Shi H, Tao K, Lu S, Sun T, Yu L, Du C, Miao J, Norford LK. Facile synthesis of 3D graphene flowers for ultrasensitive and highly reversible gas sensing. Adv Funct Mater, 2016, 26: 7462

[27] Chen Z, Wang J, Umar A, Wang Y, Li H, Zhou G. Three-dimensional crumpled graphene-based nanosheets with ultrahigh NO2 gas sensibility. ACS Appl Mater Interfaces, 2017, 9: 11819

[28] Wang Z-Z, Zheng Q, Yu M-J, Cao M-S. Multidimensional micro-nano heterostructures composed of nanofibers and micro dodecahedrons for electromagnetic wave attenuation and energy conversion. J Mater Sci Technol, 2025, 228: 1

[29] Han C, Zheng Q, Xiang K, Zhang M, Cao M-S. Self-assembly of one-dimensional cobalt-carbon to turn dielectric properties for electromagnetic attenuation. Carbon, 2025, 236 ArticleID: 120103

[30] Choi H, Shin J, Bae J, Lee S, Hwang S, Jang G, Mun S-A, Kim CH, Han I, Roh JW, Kim K-T, Lee S. Tissue-adaptive, adhesive, and ultra-conformal polymer nanomesh-based implantable bioelectrode for long-term stable electrical stimulation. Adv Healthc Mater, 2026, 15 ArticleID: e05934

[31] Dong M, Zhou L, Wang J, Wang G, Zhang X, Guo S, Wu N. Versatile cellulose nanofiber assisted preparation of magnetic carbon/MXene aerogel for broadband microwave absorption and infrared stealth. Carbon N Y, 2026, 252 ArticleID: 121414

[32] Ferrari AC, Basko DMJNN. Raman spectroscopy as a versatile tool for studying the properties of graphene. Nat Nanotechnol, 2013, 8: 235

[33] Ferrari AC, Meyer JC, Scardaci V, Casiraghi C, Lazzeri M, Mauri F, Piscanec S, Jiang D, Novoselov KS, Roth SJ. Raman spectrum of graphene and graphene layers. Phys Rev Lett, 2006, 97 ArticleID: 187401

[34] Liu S-d, Li D-s, Yang Y, Jiang LJ. Fabrication, mechanical properties and failure mechanism of random and aligned nanofiber membrane with different parameters. Nanotechnol Rev, 2019, 8: 218

[35] Hwang GS, Giapis KP. Aspect-ratio-dependent charging in high-density plasmas. J Appl Phys, 1997, 82: 566

[36] Sugiura H, Kondo H, Tsutsumi T, Ishikawa K, Hori M. Effects of ion bombardment energy flux on chemical compositions and structures of hydrogenated amorphous carbon films grown by a radical-injection plasma-enhanced chemical vapor deposition. C, 2019, 58

[37] Santhosh NM, Filipič G, Kovacevic E, Jagodar A, Berndt J, Strunskus T, Kondo H, Hori M, Tatarova E, Cvelbar U. N-graphene nanowalls via plasma nitrogen incorporation and substitution: the experimental evidence. Nano-Micro Lett, 2020, 12: 53

[38] Jiang N, Wang H, Zhang H, Sasaoka H, Nishimura KJJoMC. Characterization and surface modification of carbon nanowalls. J Mater Chem, 2010, 20: 5070

[39] Lee G, Yang G, Cho A, Han JW, Kim J. Defect-engineered graphene chemical sensors with ultrahigh sensitivity. Phys Chem Chem Phys, 2016, 18: 14198

[40] Lim N, Kim H, Pak Y, Byun YT. Enhanced NO₂ sensing performance of graphene with thermally induced defects. Materials, 2021, 14 ArticleID: 2347

[41] Schedin F, Geim AK, Morozov SV, Hill EW, Blake P, Katsnelson MI, Novoselov KS. Detection of individual gas molecules adsorbed on graphene. Nat Mater, 2007, 6: 652

[42] Wu Z, Wang H, Ding Q, Tao K, Shi W, Liu C, Chen J, Wu J. A self-powered, rechargeable, and wearable hydrogel patch for wireless gas detection with extraordinary performance. Adv Funct Mater, 2023, 33 ArticleID: 2300046

[43] Ding Q, Luo Y, Shi W, Wang H, Li J, Zhou Y, Zhu X, Yao D, Wu Z, Tao K, Liu F, Xu P, Long H, Wan P, Huo F, Wu J. Hydrogel-based self-powered, oxygen-resistant, and flexible sensors for ultrasensitive and selective NO₂ detection. Adv Funct Mater, 2026, 36 ArticleID: e12817

[44] Hilal M, Yang W, Hwang Y, Xie W. Tailoring MXene thickness and functionalization for enhanced room-temperature trace NO₂ sensing. Nano-Micro Lett, 2024, 16: 84

[45] Zhong Y, Yuan G, Bao D, Tao Y, Gao Z, Zhao W, Li S, Yang Y, Zhang P, Zhang H, Sun X. Specific Sn–O–Fe active sites from atomically Sn-doping porous Fe₂O₃ for ultrasensitive NO2 detection. Nano-Micro Lett, 2025, 17: 276

[46] Li J, Wang H, Luo Y, Zhou Z, Zhang H, Chen H, Tao K, Liu C, Zeng L, Huo F, Wu J. Design of AI-enhanced and hardware-supported multimodal E-skin for environmental object recognition and wireless toxic gas alarm. Nano-Micro Lett, 2024, 16: 256

[47] Seto S, Kawabe H, Shi L, Shimomura Y, Oyabu T, Katsube T. Mathematical model of semiconductor gas sensor. Sens Mater, 2006, 18: 1

[48] Galdikas A, Kancleris Ž, Senulien D, Šetkus AJS, Chemical AB. Influence of heterogeneous reaction rate on response kinetics of metal oxide gas sensors: application to the recognition of an odour. Sens Actuators B Chem, 2003, 95: 244

[49] Ghorbani G, Taghipour FJS, Chemical AB. UV-activated chemiresistive gas sensor response curve analysis for the fast measurement of toxic gases. Sens Actuators B Chem, 2024, 419 ArticleID: 136396

Funding

Ministry of Science and ICT, South Korea(25-DRJoint-01)

Ministry of Health and Welfare(RS-2025-02263897)

Korea Institute of Industrial Technology(UR260019)

Korea Institute of Marine Science and Technology promotion(RS-2026-25517358)

Daegu Gyeongbuk Institute of Science and Technology

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