Is It OK to Show Interest in This Case?

[Fjortis]

So basically, he is a former (in my case) physics instructor for labs at university, he doesn't teach, just helps mark the labs and answers questions if student's have them, but he is still a full-time staff member at university (maybe he even teaches, but he won't be teaching any of my courses for sure), I'm over 18 (3rd year, 21). I finished the course for which he is an instructor, and he is Not going to be lab instructor for any more of my courses anymore. We only talked a few times about things that are related to school only. Would it be appropriate to show some kind of interest in this case? (I'd really like to) And if yes, how? ( I think telling him about it in person would be a better idea than for instance sending an email (though an email is certainly easier) or for instance maybe I should even take time and actually arrange us meeting "by accident" somehow? (I know sounds silly, but as long as it's appropriate (he and I are allowed to) I'm okay with that idea too =] )

[random20]

sounds appropriate to me

[searock]

How old is he?

[Fjortis]

Thanks,,
and I'm not sure about his exact age, but probably in his early thirties, about 31-32..
So then should I do it right after the last lab, or wait for a week or two?