U.S. Patent No. 5,686,738, directed to LED creation with monocrystalline GaN films.  Claim interpretation of “non-single crystalline buffer layer” is poly, amorphous, or both layer, not a monocrystalline layer (pages 5-6).  A growth layer is “grown on” the buffer layer directly or indirectly, allowing for various combinations including growing a monocrystalline layer directly on an amorphous layer (pages 5-6).  This specific combination is not taught in the specification and was, until more recently, though not possible (pages 9 and 12).  While 5 of 6 combinations are enabled, the specification must enable all combinations covered by the claim scope (page 13).  There is no need to spell out what is well known, but the missing combination was not known at all (pages 13-14).  Since undue experimentation would be required to create the non-taught combination, the claim is invalid for lack of enablement (page 14). 

Hindsight:  The Federal Circuit noted that the patentee sought an interpretation that included amorphous for the buffer layer.  If the specification and claims had instead indicated that the non-single crystalline buffer layer is merely not monocrystalline, then the combination problem may not have existed – amorphous would not be expressly claimed.  Even safer would have been to specifically deal with all possible combinations and then make sure to only claim those possible combinations.