Collisions - bounce of walls but not from characters (while still reacting with them)

Hi! There's the game called "Osmos". Player plays with a bubble of biological liquid that absorbs other bubbles. The bubble can move, it has inertia and it bounces off walls. But when it contacts with other bubbles it just moves through them while devouring them. I need to do something simmilar. I can make my bubble devour other bubbles but it also ricochets from them. I need my bubble to just pass through other bubbles but still fire the OnCollisionEnter event. Can you suggest some solutions?

Also, video from the game: https://www.youtube.com/watch?v=Bg-4OIXsyus