Abstract: The change of the wettabilitys of lotus leaves after been soaked in different solutions, acid(H₂SO₄),alkali (NaOH), ethanol(C₂H₅OH) and acetone(C₃H₆O),with different pH values and soaking times was investigated. The results show that pH value and soaking time have little influence on the water contact angle on the lotus leaves. The lotus leaf samples before and after the experiments were observed using scanning electron microscope(SEM)and field emission scanning electron microscope(FESEM-FEG). We find that there are no obvious changes of the surface morphology and wax crystal of the lotus leaf. Chemical composition analysis of the lotus leaves demonstrates that the inert reaction between acid-base solution and cuticular wax is the main reason of un-wettability for the lotus leaves. The main reason for the rapid loss of the superhydrophobic property of the lotus leaf samples after being soaked in ethanol and acetone solutions is that the surface morphology and cuticular wax are changed due to the high combining ability of alcohols and ketones with cuticular wax.

Key words: engineering bionics, wettability, lotus leaves, acid solution, alkali solution, ethanol solution, acetone solution