Flexible electronics is a rapidly emerging interdisciplinary technology that involves the deposition of organic, inorganic, or organic-inorganic composite materials on flexible substrates such as ductile plastic or thin metal substrates. Flexible substrates have a wide range of promising applications in healthcare, environmental monitoring, display and human-computer interaction, energy conversion, management and storage, communication, and wireless networks. Flexible substrates are a signature component of flexible electronics, and their development is mainly in the area of electronics packaging. The commonly used flexible substrate materials are natural polymers and synthetic polymers. Flexible substrates are essential for the base material of flexible electronic devices and can be obtained through molding processes. Composite substrate materials can achieve multifunction and high performance. In flexible electronics, selecting substrates with superior performance is crucial to ensure proper functionality in specific application scenarios. Substrates must also maintain strong adhesion and bonding properties during compression, tension, and torsion.