From Arduino Blog - BaTboT: a biologically inspired morphing-wing bat robot actuated by SMA-based artificial muscles.
Researchers from Centro de Automática y Robótica (Universidad Politécnica de Madrid) and from Brown University carried out a very deep research about the specific behavior of bat flight, whose ultimate goal is to replicate the capabilities of bat’s wings by means of an ad-hoc designed micro aerial vehicle (MAV).
More details on the site: http://www.disam.upm.es/~jdcolorado/BAT/BaTboT.html
you can see how it flaps by a servo they must be using muscle wire for the elbow
this image could be on fishing line for all I know...