Disclosed is an assay device, having at least one optical fiber array with wells etched in one end of each of the fibers, and several microbeads adapted to be coated with cells of the same cellular type, wherein the microbeads are designed to be accommodated, one in each well, and wherein the microbeads are encoded to indicate which cellular type it is coated with. The present invention is also useful in the manufacture of other haloalkane compounds such as HCC-250 and HCC-360. The master cylinder comprises a master piston inserted in a cylinder body.