Present and future of smart functional materials as actuators in microfluidic devices

The role of actuators in microfluidic systems is fundamental for accurate measurements and analyses, as they enable precise control over fluid flow by converting various forms of energy-including electrical, thermal, piezoelectric, and electromagnetic-into mechanical motion. The integration of actuators within microfluidic devices facilitates system miniaturization, allowing complex fluidic operations at the microscale. Actuators are essential components in micropumps, micromixers, microvalves, and other fluidic control elements, ensuring accurate handling of very small quantities of liquids. However, the selection of the material type for the actuator is highly dependent on the specific application, as well as on the material composition and structural configuration of the microfluidic device in which it will be integrated. Actuators can feature either moving or static components, and the use of hybrid materials allows for the development of innovative actuation mechanisms. Given the vast range of possible actuator-material combinations, selecting an appropriate actuation strategy is critical for optimal device performance. This review presents recent advancements in microfluidic actuation, with a particular emphasis on material innovations. It explores emerging actuator materials integrated within microfluidic channels, their fabrication and integration methods, activation mechanisms, and functional applications. Additionally, the review provides a comprehensive outlook on promising materials for future microfluidic actuator development.