The injector device used on frozen D'Argo is a standard adjustable micropipette. These are actually very common in almost all labs and will draw up and then squirt back out precise quantities of almost any liquid.
The access panel D'argo crawls through at the start of this episode looks very similar to the one he could not fit through in I, E.T. (1999), except that the first one seemed to have an inner-frame (as viewed from the exterior side) which made it too small for D'argo to fit through it.