Engineering core–sheath phase change fibers for thermal energy storage: fundamentals, fabrication, and smart applications

Abstract

Core–sheath phase change fibers (PCFs) have emerged as a transformative platform for thermal energy storage (TES), integrating latent heat storage, mechanical flexibility, and multifunctionality. This review systematically explores recent advances in the design, fabrication, and applications of PCFs, with an emphasis on how core–sheath architectures enable precise thermal regulation and leakage-free encapsulation of phase change materials (PCMs). We begin by discussing the crystallization behaviors of PCMs under spatial confinement, revealing the influence of geometric constraints, interfacial interactions and post-treatment on nucleation, crystallinity and thermophysical properties. State-of-the-art manufacturing techniques, including coaxial electrospinning, wet spinning, microfluidic jetting, and melt spinning, are evaluated for their precise architectural control, improved scalability, and enhanced encapsulation efficiency. Furthermore, this review highlights the unique role of core–sheath PCFs in electronic cooling, personal thermal management, flexible electronics, and energy systems. Despite these advances, challenges remain in achieving high PCM loading without compromising structural integrity, improving environmental sustainability, and enabling adaptive thermal performance. We conclude with a forward-looking perspective on adaptive integration, biodegradable architectures, and scalable manufacturing strategies to guide next-generation PCF development.