Next, as illustrated in FIGS 4 c and 4 d, sacrificial material 142 is used to form {TAIL ~ a layer} over {HEAD ~ the reactant permeable region} 134 and to fill the apertures 138 
Next , as illustrated in FIGS 4 c and 4 d , sacrificial material 142 is used to form { TAIL ~ a layer } over { HEAD ~ the reactant permeable region } 134 and to fill the apertures 138
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 HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH