While the majority of the technologies developed for energy storage are macrosized, the reactions involved in energy storage, such as diffusion, ionic transport, and surface‐based reactions, occur on the microscale. In light of this, microfluidics with the ability to manipulate such reactions and fluids on the micrometer scale has emerged as an interesting platform for the development of energy storage systems. Herein, the advances in utilizing microfluidic technologies in energy storage and release systems are reviewed in terms of four aspects. First, miniaturized microfluidic devices to store various forms of energy such as electrochemical, biochemical, and solar energy with unique architectures and enhanced performances are discussed. Second, novel energy materials with the desired geometries and characteristics that can be fabricated via microfluidic techniques are reviewed. Third, applications enabled by such microfluidic energy storage and release systems, particularly focusing on medical, environmental, and modeling purposes, are presented. Lastly, some remaining problems and challenges and possible future works in this field are suggested.

Synthesis of a smooth conductive film over an elastomer is vital to the development of flexible optics and wearable electronics, but applications are hindered by wrinkles and cracks in the film. To date, a large-scale wrinkle-free film in an elastomer has yet to be achieved. We present a robust method to fabricate wrinkle-free, stress-free, and optically smooth thin film in elastomer. Targeting underlying mechanisms, we applied nanoparticles between the film and elastomer to jam the interface and subsequently suppress interfacial instabilities to prevent the formation of wrinkles. Using polydimethylsiloxane (PDMS) and parylene-C as a model system, we have synthesized large-scale (>10 cm) wrinkle-free Al film over/in PDMS and demonstrated the principle of interface jamming by nanoparticles. We varied the jammer layer thickness to show that, as the layer exceeds a critical thickness (e.g., 150 nm), wrinkles are successfully suppressed. Nano-indentation experiments revealed that the interface becomes more elastic and less viscoelastic with respect to the jammer thickness, which further supports our assertion of the wrinkle suppression mechanism. Since the film was embedded in a polymer matrix, the resultant film was highly deformable, elastic, and optically smooth with applications for deformable optical sensors and actuators.