Abstract: The present invention is directed to a method for measuring the surface tension of a sample comprising providing a well plate, containing at least one well defined by well walls and an opening and forming a space for receiving the sample to be tested, bringing a probe in contact with the surface of the sample in the well, and measuring the force applied to the probe by the sample, characterized in that the walls of the well are inclined with respect to the plane defined by the opening of the well so that the cross section of the well is decreasing in the direction from the opening of the well towards the bottom of the same, so as provide a geometry resulting in a flat or convex shape of the meniscus of the sample when in the well and that at least the surface of the wall of the well facing the sample space comprises an antistatic material, and providing means for dissipating static electricity from the well. The invention also concerns a well plate for use in the method.

Abstract: The present invention is directed to a method for determining the surface activity properties of an amphiphilic substance, such as a drug, the method including a step wherein the surface tension of an aqueous solution of the said substance is measured at its air-water interface at a plurality of concentrations of said substance and determining the relationship between the surface tension and the concentration of the substance, and using the relationship so determined to predict the surface activity properties of the substance, according to which method, to the aqueous solution, a water soluble substance, which increases the surface tension of the aqueous solution is added in an amount to provide a concentration of 0.3 M up to the saturation concentration of the said substance in said solution.

Abstract: The object of the invention is a measuring device for measuring small forces and displacements having in a body (1) of the device a detector means comprising a light source (4) and a position-sensitive detector (5), and a sensing means comprising a spring means (2) to be loaded by a force to be measured and a shading means (3) mounted to this spring means (2), which shading means moves under the influence of the force loading the spring means (2) in a light source (4) of the detector means, the beam being directed towards an active surface of the detector (5). It is characterizing for the invention that the detector means and the sensing means are arranged to a common clamp (8) arranged to the body (1) of the device.

Abstract: The object of the invention is a device for measuring the surface pressure of a film formed at the interface of a liquid and gaseous phase, the device comprising a detector means and a sensor means. The detector means comprises a light source and a position-sensitive detector, the active surface of which is situated in the light beam of the light source, and the sensor means comprises a sensor which can be brought into contact with the film to be measured, and a shading means which, in correspondence with the force applied to the sensor by the film, moves in the light beam between the active surface of the detector and the light source.