## 3 Results and Discussion
### Analysis of Surface Microtexture and Roughness
#### 3.1.1 Analysis of Cu-SiC Surfaces Processed by Abrasive Materials  
Based on the analysis of SEM images (Table 2), it can be seen that mechanical processing forms chaotically arranged microchannels (grooves) on the copper surface (sample No. 1). The following values of roughness parameters were obtained for Sample No. 1: Sa = 0.3 \(\upmu\)m, Sz = 3.4 \(\upmu\)m; Sdr = 1.9%. The obtained values agree well with previously determined parameters for M1 copper processed by abrasive paper with 1200 mesh (Cu 99.9, the remainder Fe, Ni, S, As, Pb, Zn, O, Sb, Bi, Sn) [44]. Table 2 shows C and O in the surface layer of sample No. 1, in addition to the dominant element Cu (76-78 wt.%). The presence of oxygen (1-2 wt.%) is due to the oxidation process, which is realized during machining with abrasive materials [49]. The presence of carbon (19-22 wt.%), is due to the uncontrolled adsorption of non-polar molecules of saturated hydrocarbons from the environment [50] under the action of polarization of inactive hydrocarbon molecules by the electric field of the metal surface [51]. The SEM images show that samples No. 2-8 processed by abrasive materials (Table 2) have no scratches in comparison with sample No. 1. The absence of defects had the effect of reducing the roughness of samples No. 2-8 compared to sample No. 1. The surfaces of samples No. 2-8 were polished mechanically under identical conditions; the difference in the initial component composition (SiC content varied from 5 to 20 wt.%) had no significant effect on the formation of texture (roughness). Therefore, the roughness of samples No. 2-8 is almost identical: Sa = 0.1-0.2 \(\upmu\)m, Sz = 1.8-2.4 \(\upmu\)m; Sdr = 1.3-1.4%. The difference in the values of the roughness parameters is comparable with the measurement error. The absence of defects in the form scratches on samples No. 2-8 and the decrease in roughness compared to sample No. 1 is explained by the higher hardness of samples No. 2-8 (Table 1). The wear mechanism and the effect of material hardness on texture formation under the conditions of metal and ceramic surface treatment with abrasive materials have been studied in [41; 44]. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline Region & \multicolumn{4}{c}{wt.\%} & Region & \multicolumn{4}{c}{wt.\%} \\ \cline{2-10}  & C & O & Si & Cu & & C & O & Si & Cu \\ \hline
22 & 35.0 & 0.0 & 61.8 & 3.2 & 43 & 7.9 & 9.2 & 9.1 & 73.8 \\ \hline
23 & 7.5 & 0.6 & 1.4 & 90.5 & 44 & 10.3 & 9.3 & 7.9 & 72.5 \\ \hline
24 & 15.2 & 1.3 & 26.9 & 56.6 & 45 & 8.1 & 9.8 & 8.6 & 73.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._Local sites predominantly consisting of Cu and SiC were observed on the surfaces of composite samples No. 2-8 and processed mechanically. The sites designated as 5, 8, 11, 14, 17, 20, and 23 in Table 2 consist mainly of copper (90-96 wt.%) with an insignificant content of C (2-8 wt.%), Si (up to 2 wt.%), and O (up to 2 wt.%). In addition, the local sites 4, 7, 10, 13, 16, 19, and 22 (Table 2) consist mainly of Si (57-62.0 wt.%) and C (34-37 wt.%) with low copper content up to 6 wt.%. It should be noted that the oxygen content was not recorded in these local sites. Despite the fact that the energy dispersive spectroscopy is rather imprecise for determining the content of C and O, it can be concluded at a qualitative level that the elemental composition of the surfaces of Cu-SiC composite materials No. 2-8 is inhomogeneous after mechanical processing. For this reason, the practical application of composite materials after mechanical processing as a structural material in the production of microfluidic devices, systems for separating and mixing micro- and nanoliter liquids, is associated with a significant disadvantage. The disadvantage is that the functioning of microfluidic devices, systems for separating and mixing micro- and nanoliter liquids, is based on the controlling the liquid movement (e.g., three-phase contact line speed, dynamic contact angles) [52].