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