A tai chi performance fan is made of bamboo and silk. The one I have is a peony style in black silk, as pictured here in the middle --
A tai chi fan routine is, like all other tai chi routines, based on martial arts. The decorative performance fan is a safe stand-in for a martial arts war fan. These have steel ribs, either blunted or pointed. The inside bottom rib is essentially a knife with a razor-sharp cutting edge. For example --
The Tessen ("iron fan") was created by the Samurai warrior class in ancient Japan, so that they would never be unarmed in situations where their swords, bows or spears could not be carried. A decorative folding fan (Sensu) was an expensive status symbol among the feudal Japanese upper class. Everyone had one, both men and women, so a fan tucked in a waist sash was above suspicion. If attacked, a Samurai could defend himself with his war fan.
Here's a couple of short videos showing how war fans are held and used to inflict damage. The demonstrator is, of course, using a safer performance fan to illustrate the moves. All these same grips and strikes are used in tai chi fan routines as well, although in much slower motion.
My next post will be about the actual tai chi fan routine. And yes, there will be a performance video! Not of me though, LOL, but of a tai chi master.