Solar‐Boosted Paper‐Based Microfluidic Fuel Cells for Miniaturized Power Sources

Abstract Paper‐based microfluidics emerges as an innovative platform for constructing miniaturized electrochemical devices, which mainly benefit from the spontaneous capillary action of paper. Nevertheless, the capillary‐driven flow dynamics on paper are determined exclusively by the intrinsic properties of paper and fluidics, thus lacking the controllability that conventional pump‐based microfluidics can provide. Herein, an approach to regulating the capillary flow on paper is introduced by conjugating the outlets of microfluidic channels with a photothermal module for water evaporation. The capillary flow rate on paper can be handily regulated from 4 to 37 µL min⁻¹ under controllable illumination conditions. As a proof‐of‐concept, prototypical paper‐based microfluidic fuel cells integrated with the photothermal module are constructed. Their peak power density can be boosted from 0.3 up to 2.1 mW cm⁻² under the simulated sunlight irradiation. The influence of capillary flow rate on the fuel cell performance is further validated using multiphysics simulations. The present work not only provides a practically feasible method to boost the performance of paper‐based microfluidic fuel cells using solar energy, but also opens a new avenue for modulating the performance of paper‐based microfluidics, which has long been a challenge in this field.