Information about pen nibs
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Felt tip pens will be familiar to anyone who has used a whiteboard in meetings and the thick broad tips of these pens (nibs) are made of synthetic fibres or wool bound with a resin. Another variety of coloured pens for drawing use nibs that are also made from fibres such as trilobal nylon with the individual fibres bound by a resin. A cross section of such a tip is shown in the central SEM image below and the SEM image on the right shows the trilobal nylon fibres. Although circular cross section fibres are common in these pens, sometimes trilobal fibres are used to enhance capillarity and flow of the inks.

Very fine pen nibs are made from tough extruded homopolymers or copolymers and the dies through which these polymers are extruded are complex giving rise to micro engineered channels through which the ink flow to the rounded tip. Examples of these are made by the Japenese company Teibow The cross section of one such tip is illustrated in the leftmost image below. This was taken using a polarized light microscope and the colours in the section arise from different thicknesses of the polymer section. To prepare the cross section, a pen nib was removed and mounted in resin, which was then cured. Then a mircotome was used to cut a very thin cross section. The tiny groves and imperfections in the steel blade of the mircotome give rise to the directional artefacts in the image. The most interesting feature of these pen nibs are their intricate structures that are designed for pens used in different applications and using different inks.