electrolyte liquid control technique : a layered body of materials with different pore diameters achieves a balance of forces due to the capillary tube forces , as shown in figure 4 . the relation describing that balance in the fuel cell is equation where p is the gas pressure , d is the pore diameter , _s _ is the surface tension , _r _ is the electrolyte density , h is the height of the liquid , _th _ is the leakage angle , a indicates the anode side , and c indicates the cathode side .