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