A small hole is formed within each portion of the exposed membrane so that a differential pressure can be applied across {TAIL ~ the membrane} without collapsing {HEAD ~ the membrane} pores while effecting passage of liquid through the membrane 
A small hole is formed within each portion of the exposed membrane so that a differential pressure can be applied across { TAIL ~ the membrane } without collapsing { HEAD ~ the membrane } pores while effecting passage of liquid through the membrane
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH