Drop-printing with dynamic stress release for conformal wrap of bioelectronic interfaces

Bioelectronic interfaces demonstrate promising applications in health monitoring, medical treatment, and augmented reality. However, conformally wrapping these film devices onto three-dimensional surfaces often leads to stress-induced damage. We propose a "drop-printing" strategy that enables damage-free film transfer using a droplet. The droplet acts as a lubricating layer between the film and the target surface, facilitating local sliding during shape-adaptive deformation. This mechanism prevents in-plane film stretching and reduces stress concentration. Even nonstretchable and fragile films can be intactly and accurately wrapped onto delicate surfaces, such as microscale microorganisms and optical fibers. Two-micrometer-thick silicon films, without any stretchable engineering, can form conformal neural-electronic interfaces by being drop-printed on nerves and brain tissue. The interfaces achieve light-controlled in vivo neuromodulation with high spatiotemporal resolution.