Strain-Sensitive Thermochromic Smart Electronic Skin for Joint and Spine Healthcare Applications

Electronic skins (E-skins) that enable interactive and quantitative joint and spine healthcare hold transformative potential for personalized musculoskeletal rehabilitation. However, existing systems face three critical limitations: conventional strain sensors degrade with cyclic large strain due to uncontrolled crack propagation; thermal therapy lacks real-time adaptive control without feedback; and systems lack user-interactive monitoring-therapy integration. Here, iStretch, a mechano-visual-thermo adaptive e-skin is introduced that integrates durable strain sensing, dynamic heat therapy, and intuitive visual feedback via a multiphasic and bilayer architecture. The strain-sensing bottom layer utilises constrained microcrack propagation in graphene-liquid metal nanocomposites, achieving high sensitivity (GF = 281), broad sensing range (300%), and exceptional durability (10,000 cycles). Simultaneously, the thermoresponsive top layer provides dynamic visual feedback and heat modulation in response to strain. Its multifunctions are demonstrated for convolutional neural network-powered omnidirectional motion and gesture recognition, strain magnitude-adjusted thermotherapy, intuitive thermochromic overheating alerts, and quantitative cervical spine monitoring via wireless sensor arrays.