High-Density Papertronics via Laser-Written Hydrophilicity on Hydrophobic Parchment Paper.

High-resolution paper-based electronics are fundamentally limited by uncontrolled ink spreading within porous cellulose networks, which constrains device density and functional integration. Here, we introduce a laser-induced hydrophilic patterning strategy on commercially available hydrophobic parchment paper that fundamentally redefines the resolution, scalability, and design freedom of papertronics. Local laser modification converts selected regions into ink-guiding hydrophilic microchannels, enabling deterministic confinement of functional materials without wax, masks, or high-temperature processing. This strategy supports few-hundred-micrometer-scale patterning, achieving a > 200% reduction in device footprint relative to wax-based approaches and offering a clear route toward further miniaturization via optical refinement. Using this platform, we realize fully printed resistors, low-loss interconnects, interdigitated capacitors, and integrated low- and high-pass RC filters within a single paper layer, exhibiting predictable, tunable electrical behavior consistent with circuit theory. Importantly, the predominantly cellulose-based substrate preserves biodegradability and disposability, while optional elastomeric encapsulation confers environmental robustness without compromising performance. By unifying high-resolution patterning, functional integration, and environmental compatibility, this work establishes laser-patterned parchment paper as a scalable and sustainable electronics platform, bridging the gap between laboratory papertronics and deployable electronic systems.