Phonon Engineering in Two-Dimensional Materials for Thermal Devices

Phonon engineering in two-dimensional (2D) materials provides a method to regulate heat transfer for information processing and thermal management beyond conventional electronics. In 2D materials, phonon spectra, mean free paths (MFPs) and scattering channels can be strongly modified by dimensionality, defects, interfaces and external fields. This review summarizes the thermal conductivity of representative 2D materials, and outlines the main experimental techniques used to measure thermal transport. It then discusses phonon engineering strategies in 2D materials, including asymmetric geometric design, defect engineering and chemical functionalization, van der Waals heterostructures, twist-angle moiré superlattices and external-field or strain-based modulation, highlighting how these approaches reshape phonon transport. The review also surveys thermal devices based on 2D materials, such as thermal rectifiers, thermal transistors, thermal memories and other functional elements for thermoacoustic generation, thermal camouflage and thermal sensing, and compares their operating principles and performance. Finally, this review identifies the remaining challenges for achieving integrated thermal circuits and practical applications, and emphasizes the need for deeper understanding of phonon transport, further optimization of device structures and wider use of data-driven approaches in materials and device design.