The volume of {TAIL ~ sacrificial material} 142 on the surface of {HEAD ~ the substrate} 132 should, therefore, correspond to the volume of the reactant gap 140 
The volume of { TAIL ~ sacrificial material } 142 on the surface of { HEAD ~ the substrate } 132 should , therefore , correspond to the volume of the reactant gap 140
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL 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