Apparatus and {TAIL ~ methods} for controlling {HEAD ~ application} of a substance to a substrate involve the use of a functional agent that blocks the substance from or attracts the principal substance to the substrate 
Apparatus and { TAIL ~ methods } for controlling { HEAD ~ application } of a substance to a substrate involve the use of a functional agent that blocks the substance from or attracts the principal substance to the substrate
OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH