Mark Ruffalo thinks a solo movie for The Hulk' would be tough to make but ''really interesting'.

The actor - who played the famous green superhero in 'The Avengers' - accepts his character doesn't like fighting crime, but it's his inner-conflict as alter ego Dr. Bruce Banner which could make a standalone film work.

He told ''It could get very boring to watch the guy who's moping around who doesn't want to do the very thing that we're all dying to see him do.

''And so I think that's the tough part of cracking that nut. I think that's what's made it problematical in the past. But I do feel like we've gained some ground on this new version of him, which has - he's sort of turning to face himself, and I think the relationship between Banner and The Hulk as a conscious conflict, it could be really interesting.

''The one thing that I think The Hulk is terrified of is Banner, and that's never really been mined.''

The star added he loved working with motion capture technology, and wants to be a ''pioneer'' in that area along with 'The Hobbit' and 'Lord of the Rings' actor Andy Serkis, who is seen as a forerunner.

He said: ''It's so exciting. There's no limit to where we can go. I hope to be a pioneer in this space with Andy Serkis. I worked a lot with him on this.

''I'm very excited by what he's doing ... This is performance. It's completely driven by the actor and it has to be honoured as much as anything else, so that's kind of where we're heading with this technology and it's very exciting.''