## 3 Results and Discussion  
### Electrical Conductivity  
The DC electrical conductivity (\(\sigma\)) for both the thick and middle sections of microparts with respect to measurement directions is reported in Figure 3, where is shown that FD \(\sigma\) for either section of the microparts is higher than that measured across the TD. This behavior is indicative of preferred orientation of carbon fillers along FD, arising from the dominant shearing effect that prevails in the injection molding process [27]. Furthermore, it should be kept in mind that in addition to the stepped decrease in thickness of the mold cavities along FD [25], the adopted molding parameters, such as melt and mold temperatures as well as injection speed, are basically higher than those encountered in conventional injection molding (CIM) [19; 28]. As a result, the shear rate generated in \(\upmu\)IM is at least two orders of magnitude higher than that in CIM [29], which is accountable for the preferential orientation of added fillers in the microparts [30]. For instance, [PERSON] et al. [30] found that the \(p_{\text{c}}\) for  
Figure 2: (**a**) 3D view of a final micropart; (**b**) three step decrease configuration of the micropart, the arrows indicate the boundary of each section. PC/CNT microparts shifted to higher filler concentrations when compared with that of compression molding or CIM counterparts. Meanwhile, the preferred orientation of carbon fillers along the FD would be detrimental to the random formation of conductive pathways across the TD within the host matrix [19]. Therefore, the TD \(\sigma\) for the middle section is lower than their thick section counterpart, at a specified filler concentration. For instance, the TD \(\sigma\) for middle section of PS/CB 3 wt % microparts is beyond the lower limit of the measurement scale for Keithley 6514 electrometer whereas the TD \(\sigma\) for their thick section counterparts is about 5.12 \(\times\) 10\({}^{-11}\) S/cm. In addition, it is worth mentioning that the \(\sigma\) for either the thick or middle section of PS/CNT 3 wt % microparts (regardless of the measurement directions) is beyond the lower limit of the Keithley electrometer, indicating a lack of conductive pathways. This finding is consistent with the results reported by [PERSON] et al. [31] where the authors found that the \(p_{\mathrm{c}}\) for PS/CNT nanocomposites is about 5 wt % in CIM. Thus, the prevailing shearing effect in uIM would largely limit the possibility of CNT-CNT contacts in the microparts [30]. However, the values of \(\sigma\) for both sections of PS/CB 3 wt % microparts are measurable except that the TD \(\sigma\) for the middle section is out of the lower limit for the Keithley 6514 electrometer. The above description indicated that despite the intrinsically high aspect ratio and electrical conductivity of nanotubes [32], the state of dispersion of the added fillers plays a significant role in determining the \(\sigma\) of subsequent polymer nanocomposites [33]. Additionally, the ratio of FD \(\sigma\) to TD \(\sigma\), i.e., (FD/TD)\({}_{\sigma}\), for the middle section is invariably higher than that of the thick section (see Table 1), confirming that the increasing shearing effect would facilitate filler orientation along the predominant flow direction. Therefore, the values of (FD/TD)\({}_{\sigma}\) can be used as an indicator to assess the degree of filler orientation in the injection molded CPCs. Moreover, the values of (FD/TD)\({}_{\sigma}\) decrease with an incremental loading concentration of added fillers, indicating that the difference between the TD \(\sigma\) and FD \(\sigma\) minimized with increasing carbon filler concentrations. In this case, it showed that there is a higher probability to form 3D conductive pathways within subsequent moldings at higher filler loading fractions, regardless of shear-induced orientation of incorporated fillers along the flow direction.