Growth and Properties of Carbon Microcoils and Nanocoils

Various types of coiled carbon filaments have been synthesized using chemical vapor deposition and other methods. These carbon filaments exhibit unique electrical and mechanical properties due to their versatile shapes and structures. To form coiled shapes, different types of catalyst compositions and reactive gases have been explored. Generally, coiled carbon filaments are classified by coil diameter and shape (e.g., microcoil and nanocoil). In this review, coiled carbon filaments are classified into three growth mechanism categories: (1) bidirectional double helical growth; (2) bidirectional twisted growth; and (3) tip single helical or twisted growth. Next, their synthesis methods and hypothetical growth mechanisms are discussed. Then, their electrical and mechanical properties are listed. Finally, potential applications and uses of coiled carbon filament are mentioned.