## 4 Performance Characteristics
### Liquid Handling Performance  
Regarding the liquid handling performance, the ability to change the syringe inside the syringe module allows the robot to maintain its precision across a large range of volumes. Figure 7 shows the results of a gravimetrical test for different volumes by using 1 mL, 5 mL, and 20 mL syringe modules. These syringes are disposable plastic syringes that are available at local pharmacies. While we have built a syringe module that can carry a 100 \(\mu\)L syringe (80601, Hamilton), we have not performed accuracy tests with it as it is not readily available and costly. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Property** & **Actual Layer** & \begin{tabular}{c} **Syringe and** \\ **Dispensing Module** \\ \end{tabular} & **Heavy Payload Module** \\ \hline Size (mm) & 600 \(\times\) 400 * & 51 \(\times\) 52 \(\times\) 256 & 113 \(\times\) 143 \(\times\) 328 \\ \hline Stroke (mm) & 300 \(\times\) 200 * & \begin{tabular}{c} Vertical axis: 78 \\ Plunger axis: 60 * \\ \end{tabular} & 100 \\ \hline Repeatability (mm) & (X and Y axis) \(<\) 0.1 & \begin{tabular}{c} Vertical axis: \(<\)0.1 \\ Plunger axis: - *,\(\ddagger\) \\ \end{tabular} & not tested \\ \hline Speed (mm/s) & (X and Y axis) 180 & \
\begin{tabular}{c} Vertical axis: 235 \\ Plunger axis: 8 * \\ \end{tabular} & 8 \\ \hline Acceleration (mm/s\({}^{2}\)) & (X and Y axis) 3000 &
\begin{tabular}{c} Vertical axis: 235 \\ Plunger axis: 4 * \\ \end{tabular} & 4 \\ \hline Payload (N) & - & 3 & \(>\)15 \\ \hline \hline \end{tabular}  
* Default values. They can easily be changed.
* Only available in the syringe module.
* Evaluated in the liquid handling experiment.  
\end{table} 
Table 1: Performance characteristics of the actuation layer and modules. These tests were performed through non-contact dispensing using distilled water. Thus, the tip of the needle does not touch the liquid when it is dispensing the sample in order to avoid cross contamination. In every test, a small volume of air is aspirated and dispensed with the liquid to minimize the volume of liquid that remains on the tip of the needle after dispensing, a technique  
Figure 7: Liquid handling accuracy for the syringe modules in non-contact dispensing. (**a**) The labels specify the syringe size and the dispensed volume for each test, which was run 30 times to find the systematic and random errors in \(\mu\)L. (**b**) Errors in \(\mu\)L are normalised using the maximum permissible errors defined by the ISO8655. A test fulfils this standard if the errors are between \(\pm\)100%. As the standard states, the maximum permissible errors for the nominal volumes apply to every selectable volume throughout the useful volume range of the piston pipette. Therefore, the maximum systematic and the random errors allowed are \(\pm\)8, \(\pm\)40, and \(\pm\)60 \(\mu\)L and 3, 15, and 30 \(\mu\)L for the 1 mL, 5 mL, and 20 mL syringe module, respectively. There are not maximum errors for a 20 mL pipette in the ISO8655. Thus, we have selected the maximum admissible errors for a 10 mL pipette. which is called leading air gap. The leading air gap was fixed for each syringe size: 100 \(\upmu\)L for the 1 mL syringe, 300 \(\upmu\)L for the 5 mL syringe, and 2 mL for the 20 mL syringe. The tests were performed automatically using a scale with serial connection (PCB 250-3/RS, Kern and Sohn GmbH, Balingen, Baden-Wurttemberg, Germany) and controlling the robot through our API (moving the plunger and syringe up and down and the head of the robot). For all the aspirations and dispenses, the robot moves the plunger with a trapezoidal speed pattern with maximum speed of 8.34 mm/s and acceleration and deceleration of 3 mm/s\({}^{2}\). Two different diameters of the needles were used (0.96 mm and 1.7 mm). Besides that, the vertical speed is constant for all the experiments; the flow rate is different as the diameter of the plunger varies for each syringe size. As the flow rate in the 20 mL syringe is too high, the smaller needle was observed to produce splashes.