Bioinspired Bubble-Gated Strategy for Integrating a Polymer Fractal Micromesh toward Ultraconformal Electrocardiogram Monitoring.

Ultraflexible polymer electronic devices with geometry engineering are highly promising for applications in conformal implantable medical devices owing to their strain tolerance, high charge carrier mobility, and biocompatibility. However, due to molecular entanglement of polymer chains and uncontrollable capillary flows, it remains a significant challenge to fabricate high-resolution, continuous, and uniform polymer patterns via solution processes, thus limiting the performance and scalability of their devices. Herein, we introduced a bioinspired bubble-gated strategy to directionally guide capillary flows for the fabrication of fractal micromeshes based on semiconductive polymers. Inspired by hierarchical liquid transport in the tree xylem, we developed a bubble-gated microfluidic system to regulate liquid distribution, facilitating the confined assembly of large-area, uniform polymer fractal micromeshes with a long-range order. Based on these micromeshes, we fabricated ultraflexible OECTs with stable performances under simultaneous 150% strain in both the x- and y-directions. Furthermore, we engineered a highly ultraconformal electrocardiogram (ECG) detector onto a rabbit heart, providing accurate ECG signal monitoring. This strategy not only overcomes key fabrication challenges but also holds significant promise for advancing applications in implantable devices and biosensors.