Large-area and soft magnetoelastic sensing for normal and shear stress distribution toward pressure injury prevention

Pressure injuries (PIs) are prevalent clinical complications arising from excessive normal and shear stresses, severely impacting patients' lives and increasing healthcare burdens. Current prevention strategies are limited by subjective nature of nursing assessments and inadequate monitoring systems with insufficient durability, limited sensing area, and poor shear sensitivity. Here, we develop a soft, durable, large-area tri-axial stress sensing array optimized via magnetoelastic model. Thin-film encapsulation with interfacial lubrication minimizes strain in large-area multi-layer assembly, while hybrid stiffness architecture reduces interface stresses to 24% of fracture stress. This design is durable (exceeding 100 hours) and cost-effective ($100/unit). Crucially, it enabled quantitative positioning optimization to reduce peak stress by 5.7 kPa (66.8% reduction compared to empirical placements). This is the first tri-axial stress sensing system to offer full-area coverage for PIs prevention and the first to quantitatively optimize skin-interface stress, offering a practical solution to improve surgical safety and postoperative care.