Respiratory Health Monitoring System Based on “Sensing Material–Medical Device–Algorithm” Framework

Abstract

Flexible sensing technologies for dynamic respiratory monitoring face critical limitations in environmental robustness and signal resolution accuracy. To address these challenges, a humidity-sensitive dielectric material was developed through intermolecular force modulation, synergistically integrated with a hermetically sealed digital mask to establish a medical-grade respiratory monitoring platform. A novel quantitative respiratory waveform analytical model was proposed, transcending conventional flexible sensors’ capability of merely tracking respiratory rhythms to enable precise quantification of pulmonary function parameters, including peak expiratory flow (PEF) and forced vital capacity (FVC). Leveraging a Darcy’s law-based porous media gas dynamics model, a linear response mechanism was identified between sensing signals and airflow/volume parameters (R² > 0.995). Time–frequency characteristics of respiratory waveforms were extracted via synchrosqueezed wavelet transforms, revealing robust correlations between spectral signatures and physical activity intensity. Clinical validation in chronic obstructive pulmonary disease (COPD) cohorts demonstrated the system’s efficacy in detecting characteristic patterns of airway obstruction and diminished pulmonary elasticity, enabling early-stage diagnostics. Furthermore, a 1-dimensional convolutional neural network (1D-CNN) achieved high-accuracy cough event recognition (95.24% precision). A vertically integrated “sensing material–medical device–algorithm” framework is pioneered for home-based artificial intelligence (AI) respiratory disease management, advancing flexible electronics from physiological tracking to precision medical applications.

Graphical Abstract

Keywords

Flexible fibrous sensor / Digital mask / Quantitative respiratory monitoring / Pulmonary function / Artificial intelligence

References

[1] Shi C, Hu F, Wu R, Xu Z, Shao G, Yu R, Liu XY. New silk road: from mesoscopic reconstruction/functionalization to flexible meso-electronics/photonics based on cocoon silk materials. Adv Mater, 2021, 33 2005910

[2] Liu Y, He K, Chen G, Leow WR, Chen X. Nature-inspired structural materials for flexible electronic devices. Chem Rev, 2017, 117: 12893

[3] Lu C, Wang X, Liu XY. Flexible meso electronics and photonics based on cocoon silk and applications. ACS Biomater Sci Eng, 2024, 10: 2784

[4] Wu R, Ma L, Chen Z, Shi Y, Shi Y, Liu S, Chen X, Patil A, Lin Z, Zhang Y, Zhang C, Yu R, Wang C, Zhou J, Guo S, Yu W, Liu XY. Stretchable spring-sheathed yarn sensor for 3D dynamic body reconstruction assisted by transfer learning. InfoMat, 2024, 6 e12527

[5] Gao Y, Yu L, Yeo JC, Lim CT. Flexible Hybrid sensors for health monitoring: materials and mechanisms to render wearability. Adv Mater, 2020, 32: 1902133

[6] Kim MS, Almuslem AS, Babatain W, Bahabry RR, Das UK, El-Atab N, Ghoneim M, Hussain AM, Kutbee AT, Nassar J, Qaiser N, Rojas JP, Shaikh SF, Torres Sevilla GA, Hussain MM. Beyond flexible: unveiling the next era of flexible electronic systems. Adv Mater, 2024, 36 2406424

[7] Guo H-Y, Shen D-W, Chen Y-H, Feng X. Flexible modular strategy for tailored, human–machine fusion wearable electronics. Wearable Electron, 2024, 1: 244

[8] Heng W, Solomon S, Gao W. Flexible electronics and devices as human–machine interfaces for medical robotics. Adv Mater, 2022, 34 2107902

[9] Yang G, Pang G, Pang Z, Gu Y, Mäntysalo M, Yang H. Non-invasive flexible and stretchable wearable sensors with nano-based enhancement for chronic disease care. IEEE Rev Biomed Eng, 2019, 12: 34

[10] Yang C, Shen Z, Yao C, Huang S, Huang X, Mo J, Yang C, Chen M, Chen H-J, Hang T, Xie X, Liu F. Integrated strain sensors with stretchable vertical graphene networks for non-invasive physiological assessment. ACS Appl Electron Mater, 2022, 4: 964

[11] Wang L, Wang D, Wang K, Jiang K, Shen G. Biocompatible MXene/chitosan-based flexible bimodal devices for real-time pulse and respiratory rate monitoring. ACS Mater Lett, 2021, 3: 921

[12] Zhang H, Chen Z, Guo S, Lin J, Shi Y, Liu X, Ma Y. Sensock: 3D foot reconstruction with flexible sensors. Proceedings of the 2020 CHI Conference on Human Factors in Computing Systems; Honolulu, HI, USA: Association for Computing Machinery; 2020. p. 1.

[13] Liu M, Liu X, Yang F. Flexible and washable MXene@PEDOT:PSS@CS@PU pressure sensors. Sens Actuators, A, 2024, 378 115810

[14] Chen Z, Wu R, Guo S, Liu X, Fu H, Jin X, Liao M. 3D upper body reconstruction with sparse soft sensors. Soft Robot, 2021, 8: 226

[15] Alupo P, Baluku J, Bongomin F, Siddharthan T, Katagira W, Ddungu A, Hurst JR, van Boven JFM, Worodria W, Kirenga BJ. Overcoming challenges of managing chronic obstructive pulmonary disease in low- and middle-income countries. Expert Rev Respir Med, 2024, 18: 873

[16] Mortimer KM, Fallot A, Balmes JR, Tager IB. Evaluating the use of a portable spirometer in a study of pediatric asthmaa. Chest, 2003, 123: 1899

[17] Ma L, Wu R, Patil A, Zhu S, Meng Z, Meng H, Hou C, Zhang Y, Liu Q, Yu R, Wang J, Lin N, Liu XY. Full-textile wireless flexible humidity sensor for human physiological monitoring. Adv Funct Mater, 2019, 29: 1904549

[18] Schlegelmilch RM, Kramme R. Kramme R, Hoffmann K-P, Pozos RS. Pulmonary function testing. Springer handbook of medical technology, 2011, Berlin Heidelberg, Springer95

[19] Bridgeman D, Tsow F, Xian X, Forzani E. A new differential pressure flow meter for measurement of human breath flow: simulation and experimental investigation. AIChE J, 2016, 62: 956

[20] Kim D, Lee J, Park MK, Ko SH. Recent developments in wearable breath sensors for healthcare monitoring. Commun Mater, 2024, 5: 41

[21] Vicente BA, Sebastião R, Sencadas V. Wearable devices for respiratory monitoring. Adv Funct Mater, 2024, 34 2404348

[22] Yang W, Li N-W, Zhao S, Yuan Z, Wang J, Du X, Wang B, Cao R, Li X, Xu W, Wang ZL, Li C. A breathable and screen-printed pressure sensor based on nanofiber membranes for electronic skins. Adv Mater Technol, 2018, 3 201700241

[23] Yang L, Wang H, Yuan W, Li Y, Gao P, Tiwari N, Chen X, Wang Z, Niu G, Cheng H. Wearable pressure sensors based on MXene/Tissue papers for wireless human health monitoring. ACS Appl Mater Interfaces, 2021, 13: 60531

[24] Dai J, Meng J, Zhao X, Zhang W, Fan Y, Shi B, Li Z. A wearable self-powered multi-parameter respiration sensor. Adv Mater Technol, 2023, 8 202201535

[25] Zheng H, Zi Y, He X, Guo H, Lai Y-C, Wang J, Zhang SL, Wu C, Cheng G, Wang ZL. Concurrent harvesting of ambient energy by hybrid nanogenerators for wearable self-powered systems and active remote sensing. ACS Appl Mater Interfaces, 2018, 10: 14708

[26] Nam Y, Kim K-B, Kim SH, Park K-H, Lee M-I, Cho JW, Lim J, Hwang I-S, Kang YC, Hwang J-H. Synergistic integration of machine learning with microstructure/composition-designed SnO₂ and WO₃ breath sensors. ACS Sens, 2024, 9: 182

[27] Ma L, Liu Q, Wu R, Meng Z, Patil A, Yu R, Yang Y, Zhu S, Fan X, Hou C, Li Y, Qiu W, Huang L, Wang J, Lin N, Wan Y, Hu J, Liu XY. From molecular reconstruction of mesoscopic functional conductive silk fibrous materials to remote respiration monitoring. Small, 2020, 16: 2000203

[28] Wu R, Ma L, Liu XY. From mesoscopic functionalization of silk fibroin to smart fiber devices for textile electronics and photonics. Adv Sci, 2022, 9 2103981

[29] Yang Y, Li K, Lin G, Lin Y, Zheng G, Xie B, Cui L, Liu XY. Medical-grade development of flexible respiratory sensing technology: pathways for medical physics implementation and clinical pulmonary function data validation. Acta Phys Sin, 2025, 74 148702

[30] Shi C, Zorman M, Zhao X, Salmeron MB, Pfaendtner J, Liu XY, Zhang S, De Yoreo JJ. Two-dimensional silk. Sci Adv, 2024, 10: 4142

[31] Diao YY, Liu XY, Toh GW, Shi L, Zi J. Multiple structural coloring of silk-fibroin photonic crystals and humidity-responsive color sensing. Adv Funct Mater, 2013, 23: 5373

[32] Wang X, Qiu W, Liu XY. From mesoscopic reconstruction to flexible meso-electronics based on nucleation control refolding rerouting of silk fibroin materials. J Cryst Growth, 2023, 603: 126977

[33] Wang X, Qiu W, Lu C, Jiang Z, Hou C, Li Y, Wang Y, Du H, Zhou J, Liu XY. Fabrication of flexible and conductive microneedle array electrodes from silk fibroin by mesoscopic engineering. Adv Funct Mater. 2024; 34:2311535. https://doi.org/10.1002/adfm.202311535

[34] Song Y, Dan R, Li L, Xia X, Zhao J, Xu R. A flexible humidity sensor based on GO/PEDOT: PSS modified laser-induced graphene electrode. Sens Actuators, A, 2025, 387 116433

[35] Shen D, Liu Y, Yu M, Kong F, Xin B, Liu Y. Bioinspired flexible and highly responsive PVDF-based humidity sensors for respiratory monitoring. Polymer, 2022, 254 125103

[36] Luo Y, Pei Y, Feng X, Zhang H, Lu B, Wang L. Silk fibroin based transparent and wearable humidity sensor for ultra-sensitive respiration monitoring. Mater Lett, 2020, 260 126945

[37] Zhang S, Wei C, Li L, Cui J, Yuan X, Hao D, Wang H. A stable and fast-response multifunctional humidity sensor based on a polyanionic liquid containing bromide ions. Chemosensors, 2025

[38] Tripathy A, Sharma P, Pramanik S, Silva FS, Osman NABA. Armalcolite nanocomposite: a new paradigm for flexible capacitive humidity sensor. IEEE Sens J, 2021, 21: 14685

[39] Jian W, Gao Y, Hao C, Wang N, Ai T, Liu C, Xu Y, Kang J, Yang L, Shen H, Guan W, Jiang M, Zhong N, Zheng J. Reference values for spirometry in Chinese aged 4–80 years. J Thorac Dis, 2017, 9: 4538

[40] Viani L, Jones AS, Clarke R. Nasal airflow in inspiration and expiration. J Laryngol Otol, 1990, 104: 473

[41] Warren DW, Hinton VA, Pillsbury HCIII, Hairfield WM. Effects of size of the nasal airway on nasal airflow rate. Arch Otolaryngol Head Neck Surg, 1987, 113: 405

[42] Daubechies I, Lu J, Wu H-T. Synchrosqueezed wavelet transforms: an empirical mode decomposition-like tool. Appl Comput Harmon Anal, 2011, 30: 243

[43] Bidan CM, Veldsink AC, Meurs H, Gosens R. Airway and extracellular matrix mechanics in COPD. Front Physiol, 2015, 6 346

[44] Knudsen L, Ochs M. The micromechanics of lung alveoli: structure and function of surfactant and tissue components. Histochem Cell Biol, 2018, 150: 661

[45] Thomsen LH, Shaker SB, Dirksen A, Pedersen JH, Tal-Singer R, Bakke P, Vestbo J. Correlation between emphysema and lung function in healthy smokers and smokers with COPD. Chron Obstr Pulm Dis J COPD Found, 2015, 2: 204

[46] Van de Moortele T, Goerke U, Wendt CH, Coletti F. Airway morphology and inspiratory flow features in the early stages of chronic obstructive pulmonary disease. Clin Biomech, 2019, 66: 60

[47] Nozoe M, Mase K, Murakami S, Okada M, Ogino T, Matsushita K, Takashima S, Yamamoto N, Fukuda Y, Domen K. Relationship between spontaneous expiratory flow-volume curve pattern and air-flow obstruction in elderly COPD patients. Respir Care, 2013, 58: 1643

[48] Hirons B, Rhatigan K, Kesavan H, Turner RD, Birring SS, Cho PSP. Cough in chronic lung disease: a state of the art review. J Thorac Dis, 2023, 15: 5823

[49] Krizhevsky A, Sutskever I, Hinton GE. Imagenet classification with deep convolutional neural networks. Commun ACM, 2017, 60: 84

[50] Orlandic L, Thevenot J, Teijeiro T, Atienza D, editors. A multimodal dataset for automatic Edge-AI cough detection. 2023 45th Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC); 2023 24–27 July 2023.

[51] Suo J, Yang X, Leung YO, Wang J, Chen M, Liu Y, Sun H, Wang Z, Qiao X, Li WJ. Enabling natural human–computer interaction through AI-powered nanocomposite IoT throat vibration sensor. IEEE Internet Things, 2024, 11: 24761

[52] Vyas R, Doddabasappla K. FFT spectrum spread with machine learning (ML) analysis of triaxial acceleration from shirt pocket and torso for sensing coughs while walking. IEEE Sens Lett, 2022, 6: 1

[53] Doddabasappla K, Vyas R. Statistical and machine learning-based recognition of coughing events using triaxial accelerometer sensor data from multiple wearable points. IEEE Sens Lett, 2021, 5: 1

[54] Zheng Z, Xu J, Li Z, Wu X, Wang C, Yin P, Zou Y, Zhang Y, Zhou Z, Gan G, Jia S, Zhang J, Qiu C-W, Zhang Q. Wireless and multi-person respiration monitoring using facemask-integrated flexible meta-antennas. Adv Mater Technol, 2023, 8 2202096

Funding

National Natural Science Foundation of China(12074322)

China Postdoctoral Science Foundation(GZC20231401)

RIGHTS & PERMISSIONS

Donghua University, Shanghai, China