Fabrication of porous film with controlled pore size and wettability by electric breath figure method

Abstract

A novel electric breath figure (EBF) method was developed by applying an electrostatic generator to assist the common breath figure (BF) method, and it was applied to fabricate polystyrene (PS) film. FESEM images showed that these PS films have a porous structure with controlled pore size because the average pore diameter, d_a, of these PS films was about 2.30 μm at 0 V, and it gradually reduced to about 0.35 μm at 1000 V, i.e. it followed the relationship: d_a = a − b ln(ρ + c), where ρ is the voltage and a, b and c are three constants. Wetting results showed that the water contact angle, θ_w, on these PS films was also controlled because the 0 V PS film showed a θ_w value at 95.07°, and it increased to 147.09° when ρ increased to 1000 V. The reason that this EBF method can control formation of porous film was found to be a reduction in water surface tension with increasing voltage.