A fluid sample is brought into {HEAD ~ contact} with a pair of {TAIL ~ spaced apart electrodes} and a voltage is applied across the electrodes 
A fluid sample is brought into { HEAD ~ contact } with a pair of { TAIL ~ spaced apart electrodes } and a voltage is applied across the electrodes
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH