Applications of flexible and stretchable three-dimensional structures for soft electronics

The development of devices that can be mechanically deformed in geometrical layouts, such as flexible/stretchable devices, is important for various applications. Conventional flexible/stretchable devices have been demonstrated using two-dimensional (2D) geometry, resulting in dimensional constraints on device operations and functionality limitations. Accordingly, expanding the dimensions in which such devices can operate and acquiring unique functionality that is difficult to implement in 2D planar structures remain challenging. As a solution, the development of a flexible/stretchable device embedding a three-dimensional (3D) structure fabricated through the precise control of a 2D structure or direct construction has been attracting significant attention. Because of a significant amount of effort, several 3D material systems with distinctive engineering properties, including electrical, optical, thermal, and mechanical properties, which are difficult to occur in nature or to obtain in usual 2D material systems, have been demonstrated. Furthermore, 3D advanced material systems with flexibility and stretchability can provide additional options for developing devices with various form factors. In this review, novel fabrication methods and unprecedented physical properties of flexible/stretchable 3D material systems are reviewed through multiple application cases. In addition, we summarized the latest advances and trends in innovative applications implemented through the introduction of advanced 3D systems in various fields, including microelectromechanical systems, optoelectronics, energy devices, biomedical devices, sensors, actuators, metamaterials, and microfluidic systems.