Figure 1
Schematic for theoretical model. Structural parameters of the thread–disk system are illustrated. The periodic rotation of the system is divided into to two stages: unwinding (from (a) to (b)) and winding (from (b) to (c)). The Cartesian coordinate system xoy is introduced, where the origin o is located at the clamped end of the string, and x and y axes are along and perpendicular to its length direction, respectively. The lengths of the string and its twisted section are denoted as l s and l st, respectively. The length of the threads is denoted as l t. The radii of the threads and the disk are denoted as r t and r d, respectively. The distance between the center of the disk and the holes is r h.
