# 3D Printed Microfluid Separators for Solid/Liquid Suspensions
## 3 Results and Discussion
### Separation Efficiency  
When a fluid containing a suspension of particles flows through the microfluidic separator, the design of the channel induces a centrifugal force. This force affects particles based on their mass and shape, leading to distinct movement patterns. Larger particles, possessing greater mass, experience a higher degree of inertia. Consequently, these particles are less influenced by the fluid flow and tend to deviate more from the streamline path, moving outward or settling at different positions within the channel. In contrast, smaller particles, with lower mass, have less inertia and are more likely to follow the fluid's streamline, remaining closer to the central flow path. This difference in movement patterns due to varying inertia enables the effective separation of particles based on their size and mass within the microfluidic device. Through the application of intelligent preparation and maintenance, flow chemistry can achieve highly efficient separation processes that consistently yield particles of desired sizes, minimizing waste and improving the overall reliability of the production process. Tables 1-3 summarize the performance of three different separators: SLA 1 (square cross section), SLA 2 (circular cross section), and FFF (circular cross section), tested at varying flow rates of 200 mL min\({}^{-1}\), 250 mL min\({}^{-1}\), and 300 mL min\({}^{-1}\). To account for uneven volumes at the outlets, the masses in the tables were normalized to 100 mL, enabling direct comparison of mass at each outlet for an equal volume of suspension. The efficiency is evaluated by the normalized powder mass difference (\(\Delta\)), which is calculated as the absolute difference between Outlet 1 (external stream) and Outlet 2 (internal stream). All of the masses in the tables represent average values obtained from five consecutive separation experiments. Preliminary tests were conducted using separators with smaller diameter channels; however, these tests were hindered by constant clogging, rendering them infeasible. This outcome suggests that smaller channel dimensions are not well-suited for handling these specific powders. For baby powder (Table 2), the SLA 1 separator shows the highest separation efficiency, at 200 mL min\({}^{-1}\), with a \(\Delta\) of 0.1449, indicating a clear distinction between Outlet 1 and Outlet 2. When fluid flows through a channel with a curvature, a velocity mismatch occurs due to the varying distances the fluid must travel along the inner and outer edges of the curve. This discrepancy in velocity within the curved section of the channel leads to the formation \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **Mean Diameter (\(\mu\)m)** & \(\sigma\) (\(\mu\)m) & **R\({}^{2}\)** & **PDI** \\ \hline Baby powder & 12.30 & 2.81 & 0.980 & 0.052 \\ Calcium carbonate & 2.06 & 1.96 & 0.997 & 0.905 \\ Quartz sand & 147.67 & 7.00 & 0.955 & 0.002 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: PSD statistical parameters for each pre-separated sample. \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 \hline
**Outlet 1** & 0.2895 g/100 mL & 0.1484 g/100 mL & 0.1428 g/100 mL \\
**Outlet 2** & 0.1447 g/100 mL & 0.1627 g/100 mL & 0.1859 g/100 mL \\ \(\Delta\) & 0.1449 & 0.0143 & 0.0431 \\
**Outlet 1** & 0.0976 g/100 mL & 0.1354 g/100 mL & 0.2697 g/100 mL \\
**Outlet 2** & 0.1533 g/100 mL & 0.1253 g/100 mL & 0.2595 g/100 mL \\ \(\Delta\) & 0.0557 & 0.0101 & 0.0102 \\
**Outlet 1** & 0.2927 g/100 mL & 0.2979 g/100 mL & 0.2695 g/100 mL \\
**Outlet 2** & 0.2924 g/100 mL & 0.2507 g/100 mL & 0.2687 g/100 mL \\ \(\Delta\) & 0.0003 & 0.0472 & 0.0008 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Normalized masses of baby powder after separation for all separators. of secondary flows, which are perpendicular to the primary flow direction.