Method of manufacturing ion-selective membranes

#The present disclosure relates to a method of manufacturing membranes of a predetermined thickness consisting of an ion-selective material, a membrane manufactured by this method and a sensor comprising a membrane manufactured by this method.

#Membranes consisting of ion-selective material, like e.g., ion-selective glass, are commonly used in various types of sensors. Examples are electrochemical sensors, like e.g., potentiometric sensors, applied in laboratories as well as in industrial applications to measure a variable of a medium, like e.g., an activity or a concentration of an analyte included in the medium or a pH-value of the medium.

#Potentiometric sensors generally comprise a measuring half-cell and a reference half-cell. The measuring half-cell comprises an electrolyte, an electrode extending into the electrolyte and an ion-selective membrane, having an inside surface exposed to the electrolyte located inside the measuring half-cell and an outer surface exposed to the medium. Due to the ion-selective interaction of the membrane with the medium, an electric measurement potential corresponding to the variable to be measured can be derived via the electrode. Quantitative determination of the variable is, e.g., performed based on the measurement potential, e.g., by determining a difference between the measurement potential and a reference potential, like e.g., a reference potential provided by a reference-half cell.

#The described embodiments and other features, advantages and disclosures contained herein, and the manner of attaining them, will become apparent and the present disclosure will be better understood by reference to the following description of various embodiments of the present disclosure taken in junction with the accompanying drawings, wherein:

#FIGS. 1a-1c show steps of a method of manufacturing a set of membranes;

#FIG. 2a shows a cross-sectional view of a membrane;

#The present disclosure includes a method of manufacturing sets of disc-shaped membranes 1 having a predetermined thickness and consisting essentially of an ion-selective material. Individual method steps a) to c) are illustrated in FIGS. 1a-1c. The ion-selective material can, e.g., be an ion-selective glass, an ion-selective polymer or another crystalline or non-crystalline solid. To this extent, one of the various types of ion-selective materials known in the art and/or applied as ion-selective material of membranes used in electrochemical and/or potentiometric sensors known in the art can be applied. Examples are ion-selective glasses, like e.g., hydrogen ion (H+) ion-selective glasses. H+ ion-selective glasses are commonly referred to as pH glasses and comprise a range of glasses suitable for various applications. Examples are pH-glasses suitable for high temperature applications, as well as pH-glasses chemically resistant to solutions of hydrogen fluoride. As another example, ion-selective crystalline solids, like e.g., fluoride (F+) ion-selective lanthanum trifluoride (LaF3) or ion-selective polymers, like e.g., sulfonated tetrafluoroethylene based fluoropolymer-copolymers, can be used.

#The method comprises a preparatory step of providing a spreadable base material 3. This base material 3 comprises all constituents of the ion-selective material and can be transformed into the ion-selective material. As an example, the base material 3 is, e.g., provided in form of a melt of the ion-selective material transformable into the ion-selective material by cooling it to a temperature below a melting point of the ion-selective material. As another example, the base material 3 is, e.g., provided in form of a powder that can be transformed into the ion-selective material, e.g., by melting the powder and subsequently cooling the melt produced by melting the powder to a temperature below the melting point of the ion-selective material.

#In step a) a quantity of the base material 3 is dispensed onto a top side of a tray 5 comprising a set of coplanar flat surface segments 7, each surface segment 7 having a surface area corresponding to a disc area of one of the membranes 1 to be manufactured on the tray 5. In addition, the entire tray 5 or at least its top side consists essentially of a material, like e.g., tungsten or a ceramic material, to enable the dispensed base material 9 to be distributed across the top side of the tray 5 and for the ion-selective material attainable by transforming base material 3 into ion-selective material on the tray 5 to be lifted off the tray 5. In other words, the tray 5 is configured as a non-stick or non-adhesive tray 5 with respect to the base material 3, the base material 3 transforming into ion-selective material on the tray 5, and the ion-selective material attained by this transformation.