Does the material and shape of the vane for an angle of attack sensor have to be identical to the material and shape of the wing? What properties should I consider?
A wide variety of materials would suffice as an AOA sensor merely aligns itself with the wind as a weather vane and does not carry load. Any non-warping reasonably strong material such as aluminum plate can be used in the design.
Since we are only measuring wind direction, look no further than old style delta shaped weather vanes, also found on turbine style wind mills.
Another quick AOA sensor could be a smoke trail, a ribbon, or a string. It just needs to follow the wind stream.
A symmetrical wing shape would work fine, a flat plate is easier to construct and is adequate to the task.