Functional microfluidics is a rapidly developing field that integrates microfluidic devices with various functions for applications in multiple areas. This review summarizes recent advances in the theory, microfabrication, and applications of functional microfluidic devices. The theory of microfluidics is based on capillary forces and surface wettability, which are fundamental to understanding fluid behavior in microchannels. The development of microfluidic devices has been significantly influenced by advancements in materials science and fabrication techniques, leading to the creation of devices with complex structures and functions. These devices are used in various applications, including heat sinks, clean water production, chemical reactions, sensors, biomedicine, capillary circuits, wearable electronic devices, and microrobotics. The review also discusses the challenges and future developments of functional microfluidic devices, emphasizing their potential in achieving carbon neutrality. The review highlights the importance of interdisciplinary collaboration in advancing the development and applications of functional microfluidic devices. The theoretical developments of microfluidics include the study of wettability, driving forces, and hydrodynamics within microchannels. Simulation methods such as computational fluid dynamics (CFD), molecular dynamics (MD), and lattice Boltzmann method (LBM) are used to model and analyze microfluidic phenomena. The materials and fabrication methods for functional microfluidic devices include polymers, metals, glass, silicon, and ceramics. Various fabrication techniques such as laser methods, molding, imprinting, lithography, and etching are used to create microfluidic devices with complex structures. 3D printing methods are also used to fabricate functional microfluidic devices with high precision. The review emphasizes the importance of these advancements in the development of functional microfluidic devices for various applications.Functional microfluidics is a rapidly developing field that integrates microfluidic devices with various functions for applications in multiple areas. This review summarizes recent advances in the theory, microfabrication, and applications of functional microfluidic devices. The theory of microfluidics is based on capillary forces and surface wettability, which are fundamental to understanding fluid behavior in microchannels. The development of microfluidic devices has been significantly influenced by advancements in materials science and fabrication techniques, leading to the creation of devices with complex structures and functions. These devices are used in various applications, including heat sinks, clean water production, chemical reactions, sensors, biomedicine, capillary circuits, wearable electronic devices, and microrobotics. The review also discusses the challenges and future developments of functional microfluidic devices, emphasizing their potential in achieving carbon neutrality. The review highlights the importance of interdisciplinary collaboration in advancing the development and applications of functional microfluidic devices. The theoretical developments of microfluidics include the study of wettability, driving forces, and hydrodynamics within microchannels. Simulation methods such as computational fluid dynamics (CFD), molecular dynamics (MD), and lattice Boltzmann method (LBM) are used to model and analyze microfluidic phenomena. The materials and fabrication methods for functional microfluidic devices include polymers, metals, glass, silicon, and ceramics. Various fabrication techniques such as laser methods, molding, imprinting, lithography, and etching are used to create microfluidic devices with complex structures. 3D printing methods are also used to fabricate functional microfluidic devices with high precision. The review emphasizes the importance of these advancements in the development of functional microfluidic devices for various applications.