# 3D Printed Microfluid Separators for Solid/Liquid Suspensions
## 3 Results and Discussion
### Determination of Particle Size Separation Capability  
The findings evaluate the effectiveness of a particle separation process based on laser diffraction measurements (Figures 9-11), focusing on characteristic particle size metrics before and after separation (Tables 6-8) at two distinct outlets (Outlet 1 and Outlet 2) with a flow rate of 200 mL min\({}^{-1}\). As determined by the difference in normalized powder mass, the best separators for each powder were measured. The SLA 1 was 200 mL min\({}^{-1}\) for baby powder and calcium carbonate, and the FFF was 200 mL min\({}^{-1}\) for quartz sand. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Flow Rate** & **200 mL min\({}^{-1}\)** & **250 mL min\({}^{-1}\)** & **300 mL min\({}^{-1}\)** \\ \hline
**Outlet 1** & 0.2598 g/100 mL & - & 0.2830 g/100 mL \\
**Outlet 2** & 0.3854 g/100 mL & - & 0.3496 g/100 mL \\ \(\Delta\) & 0.1255 & - & 0.0666 \\  & **SLA 2** & & \\
**Outlet 1** & 0.2421 g/100 mL & 0.2809 g/100 mL & 0.4018 g/100 mL \\
**Outlet 2** & 0.3652 g/100 mL & 0.3410 g/100 mL & 0.2250 g/100 mL \\ \(\Delta\) & 0.1230 & 0.0601 & 0.1767 \\
**Outlet 1** & 0.2193 g/100 mL & 0.2947 g/100 mL & 0.3548 g/100 mL \\
**Outlet 2** & 0.4456 g/100 mL & 0.3471 g/100 mL & 0.3011 g/100 mL \\ \(\Delta\) & 0.2263 & 0.0523 & 0.0537 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Normalized masses of quartz sand after separation for all separators. Figure 9: PSDs of baby powder before and after separation at 200 mL min\({}^{-1}\); laser diffraction analysis. The modus diameter before separation was 20 \(\upmu\)m, indicating a predominance of fine particles. Post-separation, Outlet 1 exhibited a dominant size of 352 \(\upmu\)m, while Outlet 2 showed a modus diameter of 315 \(\upmu\)m. This indicates that Outlet 1 predominantly contains slightly larger particles compared to Outlet 2. The significant difference in modes (352 \(\upmu\)m vs. 315 \(\upmu\)m) suggests that Outlet 1 is more effective in capturing the bigger particles, while Outlet 2 retains slightly smaller particles on average. The median (x50) indicates the particle size at which 50% of the sample's mass is composed of particles smaller than this value. The median particle size before separation was 16 \(\upmu\)m. After separation, Outlet 1 had a median of 349 \(\upmu\)m, and Outlet 2 had a median of 325 \(\upmu\)m. This difference (349 \(\upmu\)m vs. 325 \(\upmu\)m) further underscores the trend seen with the mode; Outlet 1 tends to collect larger particles more efficiently than Outlet 2. The median values indicate that Outlet 1's particle distribution leans more towards larger sizes, whereas Outlet 2 has a slightly lower median size. The Sauter mean diameter (x3,2) is defined as the diameter of a sphere that has the same volume-to-surface area ratio as the particle distribution. The initial Sauter mean diameter was 44 \(\upmu\)m. Post-separation, the Sauter mean diameter increased to 1182 \(\upmu\)m for Outlet 1 and 967 \(\upmu\)m for Outlet 2. The Sauter mean diameter is sensitive to larger particles, and the significant difference between Outlet 1 and Outlet 2 (1182 \(\upmu\)m vs. 967 \(\upmu\)m) confirms that Outlet 1 contains a greater proportion of larger particles. This also highlights the efficiency of Outlet 1 in segregating bigger particles compared to Outlet 2, which can be explained by greater inertia and less turbulent flow. In flow chemistry, the ability to modify flow rates through flexible control systems is crucial for optimizing the separation of particles by size, ensuring that the process remains efficient and adaptable to various conditions. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Before Separation** & **Outlet 1** & **Outlet 2** \\ \hline \(d_{\text{mode}}\) (\(\upmu\)m) & 20 & 352 & 315 \\ \(d_{50}\) (\(\upmu\)m) & 16 & 349 & 325 \\ \(d_{3,2}\) (\(\upmu\)m) & 44 & 1182 & 967 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: PSD parameters introduced as characteristic diameters for baby powder in SLA 1 separator at 200 mL min\({}^{-1}\).