Deformation- and damage-free transfer of soft electronics onto highly curved and fragile biological surfaces.

Seamless integration of soft electronics with biological tissues enables high-fidelity physiological sensing by maintaining intimate mechanical and thermal contact. However, transferring these devices onto highly curved and fragile surfaces remains challenging, as conventional methods often induce strain, thermal distortion, or tissue damage. To address these challenges, we introduce a deformation-decoupling, adhesion-switchable yield-stress fluid (DAYS-fluid) that enables non-invasive, damage-free transfer of soft electronics onto complex biological surfaces, including those with undercuts and negative curvature. DAYS-fluid undergoes a reversible solid-to-liquid transition at an ultra-low yield stress of 0.0253 kPa, far below the rupture pressure (~0.2 kPa) of extremely fragile biological substrates such as raw egg yolk. This low yield stress, combined with tunable viscosity, decouples fluid motion from embedded electronics, preserving structural integrity during transfer. A water-triggered adhesion-switching mechanism further reduces interfacial adhesion to near zero, enabling gentle detachment. We demonstrate high-fidelity thermal sensing on moving joints, without compromising device performance or tissue integrity.