走査電子顕微鏡による新規な撥水処理評価法の検討

抄録

Observation of water droplets of approximately 1 μL using an optical camera（OC）is generally performed using a contact angle meter to evaluate the material surface and to design an optimal surface structure for controlling water repellency. In this study, scanning electron microscopy（SEM）was used for detailed evaluation of water droplet evaporation processes. Under atmospheric pressure, we observed droplets of approximately 1 μL positioned at a specific location on a substrate. The evaporation revealed that changes of the contact angle, the contact baseline diameter, and the decrease in height versus the water droplet volume exhibited similar tendencies for the OC method under atmospheric pressure and the SEM method under 650 Pa, irrespective of the substrate temperature. Furthermore, using SEM observation of a water droplet on a substrate with a structure to facilitate water repellency, it was possible to observe fine changes accompanying the pinning effect in the droplet, in addition to fine changes of the contact interface of water droplets influenced by the substrate surface structure. Observing these features using the OC method is difficult. In summary, results show that the SEM method is effective, along with evaluation using the OC method, for evaluating water droplet evaporation.