The main train station in Saint-Étienne is Chateaucreux station. The closest to the Hubert Curien Laboratory is Carnot station (but Chateaucreux is nearly as easy with the tram). See http://www.sncf.fr
Lyon Saint-Exupéry airport (25 km East of Lyon or 70 km of Saint-Étienne). The Rhônexpress Express Tram is the fastest, most reliable and a seamless link between the centre of Lyon and the Lyon-Saint-Exupéry Airport, with a journey time of less than 30 minutes and no risk of congestion. The Rhônexpress links Lyon-Saint-Exupéry Airport with: the Lyon Part-Dieu Station. If you arrive in Saint-Étienne by the train from Lyon Part-Dieu station, stop at "Gare de Saint-Etienne Chateaucreux" and then you can take the tram number 2 (direction "Terrasse" or "Hopital Nord"), the Hubert Curien Lab is near the tram stop "Chaléassière".