Optical metrology of characterizing wetting states

The unique properties of superhydrophobic surfaces have already been widely introduced into many applications and play a more and more important role in our daily life. However, different wetting states will lead to different properties and performances so that distinguishing the wetting states is essential. Until now, as it lacks an accurate and nondestructive technology to test the wetting states in real time, this prevents the study of superhydrophobic phenomena and their applications. Although this has already caught the attention of the scientific community, there is still no successful solution presented yet. Here, we develop a nondestructive in situ optical technology based on characterizing the transmission spectrum of the superhydrophobic surfaces, which is capable of distinguishing the different wetting states such as the Cassie-Baxter state, the mixed wetting state, and the Wenzel state. By using the finite-difference time-domain method, field distribution and transmission spectrum of the superhydrophobic surfaces can be simulated. The experimental data fit well with simulation data. All the results prove the feasibility of the new optical technology to characterize wetting states.</p>