Multi-modal Wearable Patch for Localized Monitoring of Post-operative Skin Flap Transplantation

Monitoring the status of skin flap transplantation (SFT) is crucial for early intervention, particularly to mitigate risks, such as necrosis and complications arising from poor vascularization or infection. Current clinical practices for monitoring SFT rely on intermittent gauze removal, risking secondary injury and delayed complication detection. While wearable sensors have been proposed, existing systems lack simultaneous and multi-parameter monitoring, poor wearability, and the ability to localize complications within the flap. In this study, a novel multi-modal wearable patch (MMWP) was developed to monitor the essential recovery indicator reflective of the flap condition. The MMWP employed a distributed design with strain sensors in a tic-tac-toe pattern, temperature/percutaneous arterial oxygen saturation (SpO₂) sensors around the grid, and a central humidity sensor, enabling zonal multi-parameter detection (2D spatial resolution: 20 mm × 20 mm). The MMWP exhibited high sensitivity in the strain sensor (15.1 kΩ mL^-1), temperature sensor (47.63 Ω °C^-1), humidity sensor (0.03 nF %^-1), and SpO₂ sensor (error <1% vs commercial oximeters). In a 14-day rat SFT model, the MMWP successfully localized uneven recovery between proximal and distal flap regions. Integrated with Bluetooth low energy (BLE) wireless transmission, this platform resolves the limitations of gauze-dependent monitoring and advances toward precision post-operative care.