The progress of the Casimir effect: from theory to application

The Casimir force, an attractive force between two parallel, uncharged, perfectly conducting plates separated by a small gap has attracted much attention not only because it is fascinating phenomenon in quantum electrodynamics, but also because of its important applications in microelectromechanical systems (MEMS). Although the Casimir force is extremely small, it plays a dominant role in MEMS when the distance between device components is also very small. The failure of MEMS due to stiction caused by attractive force motivates the study of repulsive Casimir force. As a result, more and more derivative concepts related to the Casimir force have emerged. Aside from the attractive and repulsive Casimir forces, the lateral Casimir force can occur between sinusoidally corrugated surfaces. Casimir friction arises when two plates are in relative motion even if they are not in direct contact. Such phenomenon not only reveals the non-intuitive nature of the quantum vacuum, but also demonstrate potential applications in nanoscience and quantum technology. In addition, a rotating nanoparticle can also experience a lateral Casimir force when it rotates near a plate, the underlying mechanism is different from that occurring between corrugated surfaces. In particular, when the nanoparticle rotates in the proximity of an optically anisotropic plate, an axial Casimir force along the direction of the rotation axis is exerted on the nanoparticle. At present, these novel phenomena related to the Casimir force form the foundation of Casimir physics research. Here, we focus on the recent progress in the theoretical and experimental research on the Casimir effect including the attractive Casimir force, repulsive Casimir force, lateral Casimir force, and Casimir friction. We also review the applications of various Casimir effects in the field of nanotechnology. The Casimir effect provides new perspectives on MEMS and quantum information processing, and may inspire new experimental approaches and technological applications. This phenomenon holds substantial scientific significance and promising application potential across both fundamental research and engineering fields.