## Materials and Methods
### Drop Size Measurement  
After adjustment and starting the DRS\({}_{=1,}\) plastic cups are positioned under the dripper and dripping is established. A NeuLog Drop Counter Logger Sensor Null-223 (DCLS) fixed on a mobile stand is positioned under the dripper to register dripping. Since small drops are unable to completely interrupt the infrared beam, the DCLS is adjusted to reduce the diameter of the infrared beam by installing a piece of insulating tape with a reduced diameter opening placed at the end of the sensor that emits the beam. With this adjustment,  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Gauge Number** & **Nom** & **Min** & **Max** & \multicolumn{3}{c}{**Needle Wall Thickness**} & **Length** \\  & **OD** & **OD** & **OD** & **Type** & **Min** & **Max** & **Length** \\ \hline / & mm & mm & mm & / & mm & mm & mm \\ \hline  
\hline \end{tabular}
\end{table}
Table 1: Hypoderm needle sizes expressed as gauge number in accordance with ISO 9626:2014(E), with associated dimensions, including nominal (Nom), minimal (Min), and maximal (Max) outer (OD) diameter, wall type (TW-thin wall; RW-regular wall), thickness (ISO 9626:2014(E)), and available lengths. Notes: colors indicate the color code from ISO 6009:2016. Colors are provided only for needles used in our study. Up to gauge number 22G, all needles are 38 mm long, needles with a higher gauge number are shorter.  
even the smallest drops could interrupt the beam completely and get registered. The DCLS is connected to a laptop via a USB cable, and the NeuLog module USB 200 (NLU) from the NeuLog software application (ver. 7.311.149) is used to record. The NeuLog software provides dripping speed data. Multiple test measurements of dripping speed are performed for a period of 30 s or 60 s until the required dripping speed and pressure equilibrium in the hydraulic system of the simulator are established. The overall water drops are measured together on a precise laboratory scale (readability of 0.001 g). The mass of a single drop is calculated as the ratio of the mass difference between the plastic cup and plastic cup with collected drops, and recorded number of drops in a given unit of time. The volume of single drops is estimated from the mass value and its density, assuming a perfectly spherical shape of the drops.  
The duration of dripping per measurement lasted for 1, 2, 5 or 10 min, increasing with decreasing dripping speed and smaller drop sizes. The minimum dripping speed is determined by the capabilities of simulator to keep a constant dripping speed. For drops generated by needles with a relatively large diameter, the maximum dripping speed is determined by the proposed limit of the DCLS, whereas for relatively small drops, the maximum dripping speed is determined by the ability of the water pump to generate sufficient water pressure in the hydraulic system to increase the flow and dripping speed. Measurements are conducted starting with the minimum dripping speed and gradual increments of dripping speed for every new measurement. At least 40 measurements for all different dripping speeds were conducted for every hypodermic needle. The possible effect of evaporation on the measurement results is not taken into account.  
During the experiments, measurements of water pressure in the DRS\({}_{\text{=1}}\) system are performed for the corresponding drop sizes and dripping speed. The establishment of pressure equilibrium within the system is established by recording two identical measurements of water pressure with 1 min apart, and is ensured before starting the experiments. Given that the use of a pressure gauge usually consumes a relatively large amount of time until the establishment of water pressure equilibrium in a system, pressure measurements are performed only once for a dripping speeds of 10, 60, 120, 180, 240, and 360 drops\(\cdot\)min\({}^{-1}\).