The cross-sections of multi-channel capillaries consist of a large number of single holes, which are either in a random order or neatly arranged. Depending on the application in which these capillaries are used they can fulfill several tasks.
Two different production methods are used to manufacture multi-channel capillaries:
Prior to drawing the capillary several performs are mounted and joined together. During this process the channels are created from a single capillary. Hollow spaces are then filled with glass rods and are evacuated with heat. All unintended side channels and hollow spaces between the capillaries are sealed during this process and result in a closed cross-section, which is only punctuated with the inner geometry of the single capillaries. Reproducible profile sizes, concerning the entire diameter as well as the inner diameter of the single capillaries, can be manufactured by using thick walled capillaries. In this case, however, the closed area is partial larger than the area of the holes. The use of thin-walled capillaries for the production of the perform results in an airy structure with less closed and more free areas in the cross-section. Using thin walls the capillaries tend to deform more easily inside and are therefore not particularly suited for the production of precise inner geometries.
The second process used to produce multi-channel capillaries is laminating single capillaries with epoxy resin. This method is applied when environmental parameters, such as high temperatures or solvent resistance, do not require the use of a mere glass construction but a high accuracy of the inner diameter. In this process single capillaries are joined to an array/bundle. Hollow spaces between the capillaries are filled with an acrylate- or epoxy-based resin and cured with UV light. Various adhesives may be used depending on the application.
There are several options for the ends of the capillaries: