When it comes to writing, be interested in everything you can. Of course, there will be subjects in which you will have not the slightest inkling of interest and that's fine. There's no way I'm about to do a piece on Quantum Physics - even for the layman - because I really just don't get it. No matter how I try. I blame my 'creative' brain but I know that's a poor excuse. Bill Bryson did a fantastic job of breaking down complicated subjects into everyday, understandable languague in A Short History Of Nearly Everything and he's clearly pretty creative! But I still don't get it. How can one thing be in two places at once...I mean...how?!
But physics aside (for me at least) there are plenty more subjects out there that could provide the spark for an article. It might not be something you think you'd be interested in, but give it a chance. Make some notes, ferret around a bit with some research (although try not to get too sidetracked here at this stage) and see what turns up. An interesting character associated with the subject may crop up providing you with yet another possible article. It may be that the final article has only a tentative link with the subject you originally started with, just see where the rabbit holes can lead. Keep an open mind. Don't dismiss something immediately just because you think you're not interested in that subject. You may surprise yourself.