Could you also tell me what are the notes played by the strings from 2:40 to 2:42? Does it just play every single note chromatically from A to G?
It's not really a technique - the strings are playing 'arco' (with the bow) as usual. When we talk about techniques, we are talking about how composers instruct players to play what they have written, not what they have instructed the players to play. As for the notes, to me it sounds like an ascending diatonic pattern - this is different to a run, which is strictly ascending notes. A pattern is any sequential musical phrase. I don't think there are any chromatic notes.