Pollen‐Derived Paper for Sustainable Droplet Energy Harvesting

ABSTRACT

Harvesting electricity from raindrops offers a promising route toward distributed self‐powered electronics, but conventional devices rely predominantly on non‐renewable synthetic polymers and metals. Here, we report a pollen‐derived droplet energy harvester (PDEH) fabricated from abundant sunflower pollen. Defatting and mild de‐esterification convert rigid pollen grains into processable microgels that form free‐standing paper. Functionalization produces dielectric and conductive layers for an ultrathin multilayer device containing only 24 wt.% non‐renewable solid materials. The incorporated constituents of a 3 × 3 cm ² device cost approximately US$0.003, excluding processing consumables. Optimizing dielectric‐layer thickness and surface fluorination yields 16.8 V from a single 37 µL tap‐water droplet, with an energy‐conversion efficiency of 1.26% and a maximum instantaneous power density of 63 mW m ⁻² . The approximately 70 µm‐thick, 0.191 g device conforms to flat, curved, and irregular surfaces and maintains stable electrical output over 14 days of operation. A ten‐unit PDEH array harvests simulated rainfall to charge a 10 µF capacitor to 2 V, subsequently powering a commercial electronic clock. These findings establish pollen‐derived functional paper as a low‐cost platform for droplet energy harvesting and demonstrate its potential for renewable‐material‐based, distributed self‐powered electronic systems that combine renewable feedstocks, mechanical conformability, and energy storage for practical applications.