A gas sensor is disclosed which attains high response speed, low power consumption, superior water splash resistance and a little setting direction dependency and setting angle dependency. The device employs mechanical centrifugal forces to concentrate liquid droplets in a limited space for further extraction from the gas flow using an electrical field and an electrically charged collecting surface whereby the particles are attracted to and deposited on the surface for further extraction by the gas flow without reintrainment of the liquid back into the vapor stream. Portions of the gel layer are irradiated to pattern the gel layer and to form exposed portions.