Abstract: A device for detecting a geometry of a drop arranged on a sample surface includes a metering apparatus comprising a liquid reservoir and an outlet opening and a plurality of light sources configured to direct light onto a surface of the drop of liquid. A camera is configured to detect a reflection of the light from the surface of the drop of liquid. The device includes a housing including a recess that forms a cavity that is configured to be separated from external surroundings when the housing is arranged on the sample surface. The plurality of light sources are arranged in the cavity and cover a solid angle of at least ?/2 sr when viewed from a point on the sample surface. At least a portion of the metering apparatus is positioned inside the cavity.

Abstract: A method for measuring a receding contact angle between a sample surface and a drop of a liquid is provided. The method includes ejecting a dosing volume of the liquid from an opening onto the sample surface such that the liquid is ejected as a continuous jet at a defined flow rate for a defined dosing time period, and the opening comprises an opening diameter. The dosing volume of the liquid is allowed to form a drop on the sample surface. At least one geometrical parameter of the drop formed on the sample surface is measured and a contact angle between the sample surface and the drop is determined based on the at least one geometrical parameter. The flow rate and the dosing time period are selected such that the dosing volume does not exceed the flow rate multiplied by 0.11 s.

Abstract: A method for analyzing an interaction between a sample surface and a drop of liquid comprises applying the drop of liquid to the sample surface and illuminating the drop of liquid using at least two light sources. The at least two light sources are each arranged at a light source position surrounding the drop of liquid. Light reflected from the drop of liquid detecting and a sensor position on a sensor of a camera is determined for each detected light reflection. Light source positions are assigned to individual light source positions. A position of the drop of liquid is calculated relative to the sensor and an item of size information of the drop of liquid is determined. The position and the item of size information are calculated from the pairs of one sensor position and one associated light source position.

Abstract: A drop on a sample surface in a gaseous environment has a curved surface with a symmetry axis and a defined volume. To determine the contact angle, an object is imaged based on the reflection property of the surface of the drop, the position of the object with respect to the optical axis of an optical measuring system and the position of the object with respect to the sample surface, with the symmetry axis of the drop being arranged in or in the vicinity of the optical axis. The distance between the image and the optical axis of the drop is measured. The radius of curvature of the drop is determined based on the measured distance, and the contact angle is determined from the radius of curvature.