Table 1.
Comparison of portable electronic devices for OA applications.
| Mechanism | Materials | Application | Sensitivity | Response Time | Linearity/Rang | Fatigue Life/Stability | Biocompatibility | Development Status (TRL) | Ref. |
|---|---|---|---|---|---|---|---|---|---|
| Piezoresistive | Electric conductive rubber sensors | Gait rehabilitation training | Wearable | TRL 6-7 | 87 | ||||
| Hartmann hydrocoll | Monitoring system for knee extensor training | 0-90° | >40 compression cycles | Wearable | TRL 4-5 | 88 | |||
| Silica nanoparticle-reinforced polydimethylsiloxa-ne | Implantable pressure sensors for TKA | Pressure<3 MPa:5.22 MPa−1 Pressure>3 MPa:70 MPa−1 |
30 ms | 45 Pa - 4.1 MPa | >5000 compression cycles | <24 h in vivo | TRL 4-5 | 89 | |
| Capacitive | Polyacrylamide gel(PAAm)/segmented embedded hydrogels (SEHs) | Cartilage-inspired strain sensor for motion | Strain<150% GF = 6.92, Strain>150% GF = 21.98 | 93 ms | 0–350% strain | >600 compression cycles | Good | TRL 4-5 | 90 |
| Capacitive | P(EA-co-AN) ionogel | Implantable pressure sensors for TKA | 2.43 – 2.48 kPa−1 | R2 > 0.998, 0 – 2.0 MPa |
43 years | Excellent | TRL 5-6 | 91 | |
| Triboelectric | Styrene-ethylene-butylene-styrene (SEBS)/CNT/BaTiO3 (BTO) | Rehabilitation assistance (quadriceps, pulse, plantar) | 0.068 kPa−1 (<53 kPa); 0.013 kPa−1 (>53 kPa) | 25 ms | 0–660 kPa | Skin-inspired, breathable, permeable | TRL 4 | 92 | |
| CNT/acetylene black/polydimethylsilox-ane (PDMS) | Smart Insole for gait monitoring and recognition | Nonlinear synergistic strategy | R2 > 0.999 (0–225 kPa) | >180,000 compression cycles | Wearable | TRL 4-5 | 93 | ||
| PVA-borax hydrogel, polydopamine (PDA)-CNTs | Muscle motion monitoring, photothermal treatment | Self-Healing: recovers in 10 min | Wearable | TRL 4 | 94 | ||||
| Triboelectric | Conductive sponge, polyurethane sponge | Muscle telescopic monitoring | Adjustable sensitivity | 2 ms | 0.001-0.010 N | >360,000 compression cycles | Wearable | TRL 4 | 95 |
| Nylon/Eco-flex | Metaverse human-machine interaction | 0-5 Hz | 1.0-4.5 mm | Wearable | TRL 4-5 | 96 | |||
| Polytetrafluoroethy-lene (PTFE), copper foil | Smart healthcare | 15° | 15°–120° | >5000 compression cycles | Wearable | TRL 4-5 | 97 | ||
| Porous PDMS/Copper | Rehabilitation, Muscle function | 1.76 V/kPa | ∼50 ms | R2 = 0.092,0-150 kPa | >100,000 compression cycles | Wearable | TRL 4-5 | 98 | |
| PVDF/BTO/CNT | Gait analysis, motion monitoring | 66 ms | <100 kPa | >2000 compression cycles | Wearable | TRL 5-6 | 99 | ||
| Triboelectric | Thermoplastic polyurethane (TPU) | Implantable pressure sensors for TKA | R2 = 0.99, 0-350N | >30,000 compression cycles | TRL 5-6 | 100 | |||
| Piezoelectric | Multi-layered PVDF | Implantable pressure sensors for TKA | 8.5 mV/N | TRL 5-6 | 101 | ||||
| Boron Nitride Nanotubes (BNNTs)/PDMS | Joint torque monitoring, knee load | ∼120 mV/(kPa·wt%) | <50 ms | >5000 compression cycles | Wearable | TRL 4-5 | 102 | ||
| Inertial | Commercial wearable sensors | Rehabilitation exercise assessment (KOA) | Wearable | TRL 6-7 | 103 | ||||
| Multi-sensor accelerometer units | Predict improvement after exercise intervention | Wearable | TRL 6-7 | 104 | |||||
| Inertial | Commercial Pressure Mat | Pelvis-trunk motion and OA detection | External use | TRL 6-7 | 105 | ||||
| Piezoelectret | Expanded polytetrafluoroethylene (e-PTFE) | Implantable pressure sensors for TKA | 9 mV N−1 | 93 ms | R2 = 0.992 (1.4 - 13.6 N) | >4000 compression cycles | TRL 5-6 | 106 |