As respiratory diseases surge worldwide, the limitations of conventional spirometry and bulky pneumography—low patient compliance, signal distortion from motion, humidity or temperature swings—become ever more pronounced. Now, a cross-campus team led by Prof. Hailin Cong (Shandong University of Technology), Prof. Jun Yang (Beijing Forestry University) and Prof. Changyou Shao (Dalian Polytechnic University) has unveiled a high-fidelity, eco-responsible solution in Nano-Micro Letters: a cellulose-based piezoresistive sensor (CPS) that pairs MXene nanosheets with TEMPO-oxidised cellulose nanofibrils inside a customizable cylindrical micro-dome architecture, delivering interference-free, real-time respiration-rate tracking even under bending, high humidity (50–100 % RH) or 30–80 °C thermal fluctuations.
Why the New Sensor Matters
- Sustainable Core: All building blocks—TOCNF, gelatin, bacterial-cellulose encapsulation and screen-printed Ag interdigitated electrodes—are biodegradable, biocompatible and fabricated via low-cost mask-assisted vacuum filtration, cutting electronic-waste concerns.
- Motion & Artifact Immunity: A laminated “contact–separate” mechanism and shear-force-steered MXene/cellulose alignment (revealed by 5-ns molecular-dynamics simulations) dissipate off-axis stress, maintaining < ±2 % baseline drift over 25 000 breath cycles or 10 000 bending cycles (0–120°).
- Clinical-Grade Accuracy: Cylindrical domes (100–500 µm tunable) optimise strain distribution, giving 24 ms response/recovery, 90 % ML-classification accuracy (normal/fast/deep/cough) across volunteers of different ages, and stable output (≈ 2 × 10-2 A) in 95 % RH fog or 79 °C airstream.
Innovative Design and Features
- Heterogeneous Laminate: A 1-mm gelatin “suppression layer” hydrogen-bonded to an MXene/TOCNF conductive film boosts puncture force to 4 N and toughness > 65 MJ m-3 while remaining ultra-thin (120 µm) and highly vapour-permeable (WVTR up to 4 424 g m-2 d-1).
- Scalable Soft Lithography: Laser-cut stencils define dome arrays on 25 × 30 cm2 sheets; roll-to-roll pressing (2 MPa, 5 min) laminates electrode, spacer and BC encapsulation for seamless facial conformity.
- Wireless Integration: A Bluetooth module on a standard mask streams data to a smartphone; deep-learning segmentation of peak/valley patterns achieves ROC-AUC ≥ 0.96 for every breathing state—enabling at-home sleep-apnoea screening or post-surgery surveillance.
Applications and Future Outlook
- Point-of-Care & Home Health: Real-time differentiation of respiration patterns during daily activities or sports (badminton trial validated) offers early warning for asthma, COPD or COVID-19 relapse.
- Eco-Electronics Pipeline: Complete oxidative disintegration within 72 h in 4 % H2O2 and soil-burial breakdown by 150 days point to disposable, guilt-free deployment in mass fever clinics or disaster zones.
- Challenges & Roadmap: Long-term enzymatic stability, large-area MXene supply chains and regulatory biocompatibility tests are next milestones; upcoming work will integrate on-chip signal processing and energy-harvesting films for battery-free, continuous respiratory surveillance.
This work pioneers a customizable, green-materials route to high-precision wearable sensors, promising sustainable, interference-free respiratory monitoring for vulnerable populations and tele-health platforms.