Longitudinal confinement engineering in phase change materials

Amidst escalating energy demands and intensifying environmental pressures, advanced phase change materials (PCMs) have emerged as highly efficient and sustainable storage solutions, owing to their unique operational principles. However, pristine PCMs encounter a multitude of challenges, including susceptibility to leakage, inferior thermal/electrical conductivity, inadequate light responsiveness, intrinsic rigidity, and limited functionality, which impede their effectiveness in addressing the complex demands of real-world applications. Longitudinal confinement of PCMs using advanced multifunctional 1D materials is accepted as a cutting-edge solution to these limitations. A corresponding comprehensive review of longitudinally confined composite PCMs is thus imperative for subsequent studies and yet is missing from the literature, unlike reviews of 0D, 2D, and 3D materials for PCMs. Herein, this review systematically highlights the diverse roles of longitudinal materials in PCMs and analyzes the relationships between their architectures and thermophysical properties, with particular emphasis on design principles and advanced multifunctional interdisciplinary applications. Additionally, we provide an in-depth understanding of thermal transfer, energy conversion mechanisms, and rationalized routes to high-efficiency energy conversion PCMs. Finally, we introduce critical considerations for current challenges and future solutions to them, hoping to offer constructive guidance and facilitate significant breakthroughs for longitudinally confined composite PCMs in both fundamental interdisciplinary research and commercial applications.