Photoshop: Is there a way to preserve layers and blend modes when merging or saving PNG?

This is a mandatory feature particularly for game developers - we need to be able to preserve blend modes when merging or saving. Game Engines typically expect a sprite sheet, that is, a large .PNG file with each frame of animation on it for a given character or special effect. This means that everything in Photoshop must eventually get flattened or merged, and as far as I can tell, Blend Modes become utterly useless at this point. Does Photoshop support this and I'm just unaware of where to look for it?