{HEAD ~ the first element} and the second element are substantially perpendicular to {TAIL ~ the substrate surface}, wherein 
substantially perpendicular to
{ HEAD ~ the first element } and the second element are substantially perpendicular to { TAIL ~ the substrate surface } , wherein
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH