A vision system examines droplets monitoring quality and {HEAD ~ a feedback signal} to vary {TAIL ~ the material} in each droplet 
A vision system examines droplets monitoring quality and { HEAD ~ a feedback signal } to vary { TAIL ~ the material } in each droplet
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH