A Battery‐Free Low‐Cost Paper‐Based Microfluidic Actuator

This study presents a novel approach to create a low‐cost and user‐friendly water‐induced actuator based on hydrophobic papers and a simple embossing method. By injecting water onto the papers through microfluidic channels made by embossing, fast and reversible bending actuation can be induced. The actuation angle and speed are dependent on the amount and duration of the water applied, which allows the actuator to be effectively controlled by syringe injection/drawing without the need for an external power supply. A bending angle of >90° can be achieved in ≈15 s, with complete reversal attainable in ≈3 min; and the actuation can be induced again by resting for ≈1 h after the reversal. This work represents a significant contribution to the field of paper‐based microfluidics by demonstrating actuation in a battery‐free, low‐cost, and simple approach, with potential applications in paper‐based analytical devices such as medical diagnostics.