This involves flowing a fluid over {HEAD ~ the surface} wherein the fluid contains {TAIL ~ positively charged ions} and electrons 
This involves flowing a fluid over { HEAD ~ the surface } wherein the fluid contains { TAIL ~ positively charged ions } and electrons
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH