The Spinergy SPOX wheels used a kevlar spoke. I remember the rep showing me that he could tie one of the spokes in a knot. They never really caught on in the road market because of how aerodynamically infeasible they were. Turns out, 28 flexible 3.5mm-wide cylinders flying through the air (per wheel) caused a whole heck of a lot of drag. I raced with a guy back in the early 2000's that ran them and you could hear the spokes beating the air to death underneath him, and he claimed he could feel them "humming" at certain speeds, but especially in crosswinds.