A review of microvalves (2006–2025): state of the art, trends, and future directions

As microfluidic systems grow increasingly complex and application-driven, microvalves have emerged as indispensable components for the precise and programmable control of liquids and gases in integrated microscale networks. Since the influential review by Oh and Ahn in 2006 (Oh and Ahn 2006 J. Micromech. Microeng. 16 R13–39), the field has advanced substantially through innovations in actuation mechanisms, materials, fabrication methods, and system-level integration. This review presents a critical and selective overview of microvalve developments from 2006 to 2025, categorized into five principal classes: active mechanical, active non-mechanical, passive mechanical, passive non-mechanical, and non-traditional microvalves. Each category is examined through its representative technologies, including magnetic, electrostatic, piezoelectric, thermal, pneumatic, electrochemical, phase-change, rheological, capillary, and diffuser/nozzle/Tesla-type designs, together with emerging programmable, biohybrid, and artificial intelligence (AI)/machine learning (ML)-assisted architectures. Particular attention is given to the transition from conventional microelectromechanical systems and polydimethylsiloxane (PDMS)-based platforms to soft, stimuli-responsive, and additively manufactured systems that offer improved chemical compatibility, lower power consumption, and greater functional integration. The review also examines the growing role of microvalves as programmable fluidic elements in automated lab-on-a-chip systems, digital microfluidics, and logic-enabled microfluidic circuits. Finally, key challenges including leakage, durability, fabrication scalability, standardization, and commercialization barriers are critically discussed. By consolidating two decades of progress, this review provides a state-of-the-art perspective on the evolution of on-chip and off-chip microvalves, highlighting future opportunities to translate these diverse mechanisms into smart microfluidic systems, ranging from high-throughput analysis to decentralized diagnostics and therapeutics.