"Electroweak materials" sounds like materials that have very weak [i]electrostatic forces of attraction[/i], or bonds. This makes me think the Traveller 'works' utilizing easily broken and made bonds. Therefore, I would think that atoms like francium (if it were, in any way, stable enough (half life of 22 min in its most stable form)) would be used in it. Other ideas[spoiler]based on this, I would assume that a good portion of the Traveller's technologies were simply these materials, which would be created by the Traveller (not used) for reproduction. These materials would be used to create new, better things, [i]including medicine[/i] [/spoiler]