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 contact angle measurement apparatus includes a liquid reservoir arrangement, a drop dosing device in fluid communication with the liquid reservoir arrangement and adapted for applying a liquid drop onto a sample surface, an illuminating device for illuminating each drop applied by the drop dosing device and disposed on the surface from a first side, and an image recording device for recording an image of each applied drop disposed on the surface. A liquid pressurizing system is adapted to pressurize liquid from the liquid reservoir arrangement, and a controller connected to the valve of each drop dosing device and to the liquid pressurizing system, which controls the operation of the liquid pressurizing system and, for each drop dosing device, opening and closing of the respective valve to apply a drop of the respective liquid from the respective liquid line to the surface in a jet of pressurized liquid.

Abstract: Methods for fast fresh surface formation between two fluids as well as a device employing this method to measure dynamic or equilibrium interfacial tension between the fluids.