The spacers bond {HEAD ~ the substrate} to {TAIL ~ the transparent counter substrate} and maintain a prescribed cell gap 
to
The spacers bond { HEAD ~ the substrate } to { TAIL ~ the transparent counter substrate } and maintain a prescribed cell gap
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH