A source electrode and a metal pattern for a storage capacitor are formed on an insulating substrate, a silicon layer having a doped source region and a doped drain region is formed on the substrate and the source and the drain regions directly contact to the source electrode and the metal pattern. The gene encoding the J chain may be introduced by co-transfection. The supports located at the two ends of the slats of the pair of slats are secured in rotation by two transverse rods connecting the lower portions and providing a resilient return.