four parallel cells 2 which are separated from one another by triangularly shaped separator walls 3 and in each of which flows in use a carrier liquid 4 for particulate pigmented material which is used to form an image on an underlying substrate the mechanism of operation is as described in the pct applications and will not be further described herein in detail the rearwards part of each of the cells 2 is closed by side walls 5 which thus in this example define a chamber or chambers not shown behind the cells 2 the ends of the printhead are formed by tapering walls 8 each of the cells 2 has a tip or front portion with an opening in which extends the forward part 6 u2032 of an ejection electrode 6 each of which electrodes is of triangular shape as shown best in fig1 fig2 illustrates the positioning of the meniscus 7 of the carrier fluid and shows the position of the electrode tip portion 6 u2032 in each of the cells behind the meniscus 7 the triangular shape of the separator walls 3 at their front edge allows each meniscus 7 to extend further forwards than if the separators were flat or straight edged at the front and this improves ejection of the material from the carrier liquid fig3 shows an alternative embodiment in which the cell 2 formed between the rectangular separators 10 is trough like the triangular separator 9 formed in the cell at.