## 1 Introduction  
The electrohydrodynamic-jet (EHD jet) has emerged as a fine patterning tool for various applications [1]. The EHD jet process uses the high DC voltage applied at the nozzle part to charge ink and produce an electrical field for jetting [2; 3; 4; 5; 6]. For drop-on-demand (DOD) EHD jetting, an additional pulse voltage has been used to produce one droplet per pulse voltage. To design the pulse voltage shape for proper jetting, [PERSON] et al. proposed a pulse width modulation method [5], whilst [PERSON] et al. presented the use of trapezoidal pulse voltage [6]. For EHD printing, most previous works have used AC or pulse voltage with constant frequency [4; 5; 6; 7; 8]. In such cases, there will be a large amount of deposited droplets at the starting and end points, which is caused by printing speed variation. Uniformity in the printed pattern is important for most fine patterning applications, including conductive patterning, semi-conductor applications, and repair application for broken circuits. As a result, the EHD applications can be limited to the case of low printing speed, and there has been a trade-off relationship between the printing speed and print quality. Nevertheless, to the best of the author's knowledge, few papers have discussed the printing uniformity issue of the end points of the EHD printed lines.  
In the case of conventional piezo-based inkjet application, the encoder signals (positioning sensors in stages) have been used for bitmap printing to obtain equally spaced printing irrespective of the printing speed. However, the conventional inkjet printing uses only one axis of the encoder signal for the main direction printing, while the other axis is used for movement of the printing location for the next swath. The conventional method using encoder signals from a single axis is useful to print bitmap images by using inkjet heads with many nozzles. However, in the case of EHD printing, a single nozzle is more commonly used, since the multi-nozzle EHD head is difficult to implement, because of the electrical crosstalk effects from adjacent nozzles. In such a case, vector printing using a single nozzle rather than bitmap image printing is more suitable for its application. Vector printing commonly involves the vector motion of stages that require the simultaneous movement of more than two axes. Therefore, the hardware and software algorithm requirements for vector printing should be different from those for bitmap printing.  
In this article, we propose a new vector printing method for EHD jet printing to print uniform lines by printing dots with equal spacing, irrespective of printing speed variation. For this purpose, the jetting trigger pulses are generated at each equally spaced distance based on two position encoder sensors. Here, two different approaches are proposed: (1) the printing method, including acceleration and deceleration regions; and (2) the printing method using only the constant printing speed region, excluding the acceleration and deceleration regions. To implement the proposed method, a so-called encoder processing unit (EPU) and a built-in computer-aided design (CAD) printing software were developed, so that positioning sensors from two axes (two encoder signals) could generate the trigger pulses at each pre-set distance along the printing line. Finally, we compared our proposed printing methods with the conventional method by investigating the end points of the printed lines according to the printing speed.