## 3 Design of the Experimental Test  
The experimental setup is established as shown in Figure 3 to demonstrate the performance characteristics of the proposed piezoelectric jetting dispenser while considering various operating parameters. The piezoelectric actuator AE0505D44D40 DF (TOKIN Corp., Miyagi, Japan) is selected, and the specification of the piezoelectric actuator provided by the manufacturer are given in Table 2. The displacement of the needle according to the input voltage is measured by increasing the input voltage from 0 V to 150 V by 15 V. The measured displacement is presented in Figure 4, and the maximum displacement of the needle is about 390 \(\upmu\)m at an input voltage of 150 V. The displacements for 120 V and 135 V input voltages are 300 \(\upmu\)m and 345 \(\upmu\)m, respectively, thus larger than the minimum displacement for effective dispensing, 300 \(\upmu\)m [15]. The weight of a single jetted dot is measured by using a precision balance, WZA245-NC (SARTORIUS Corp., Gottingen, Germany). The maximum measurable weight and the measurement resolution are 240 g and 0.01 mg, respectively. In order to create jetting parameters that are similar to those required in industrial applications, a mixture of 85% silicone (OE-6630, DOW CORNING, Auburn, MI, USA), that is widely used in LED applications, and 15% yellow phosphor-yttrium-aluminum garnet (YAG, NICHIA Corp., Tokushima, Japan) is used as the dispensing fluid. The material properties of the dispensing fluid are listed in Table 3.  
Figure 2: Operating process for the jetting. (**a**) Needle position; (**b**) input voltages. \begin{table}
\begin{tabular}{c c} \hline
**Parameter** & **Value** \\ \hline Dimensions & \(5\times 5\times 40\) mm \\ Blocking Force & \(750\) N \\ Maximum Displacement & \(42\) μm @ \(150\) V \\ Stiffness & \(20.2\) N/ μm \\ Resonant Frequency & \(34\) kHz \\ Rising Time & \(20.32\) μs \\ Falling Time & \(26.68\) μs \\ \hline \end{tabular}
\end{table} 
Table 2: Specifications of the piezoelectric actuator. Figure 4: Measured needle displacement according to the input voltage. Figure 3: Experimental setup for the jetting test. \begin{table}
\begin{tabular}{c c c} \hline
**Material** & **Property** & **Value** \\ \hline \multirow{4}{*}{Silicone (OE-6630)} & Viscosity & \(2300\) cp \\ \cline{2-3}  & Surface Tension & \(2.2\times 10^{-6}\) N/cm \\ \cline{2-3}  & Density & Part A & \(1.10\) g/cm\({}^{3}\) \\ \cline{2-3}  & Part B & \(1.15\) g/cm\({}^{3}\) \\ \hline Phosphor (YAG) & Density & \(4.40\) g/cm\({}^{3}\) \\ \hline Mixture & Mixture & \(1.20\) g/cm\({}^{3}\) \\ (Part A:Part B = 1:1 and Phosphor 15\%) & Density & \(1.20\) g/cm\({}^{3}\) \\ \hline \end{tabular}
\end{table} 
Table 3: Material properties of the dispensed fluid. It is necessary to evaluate the accuracy and precision of the jetted amount of fluid with respect to the operating parameters to identify the performance characteristics of the proposed piezoelectric jetting dispenser. The important operating parameters can be broadly divided into two parts. One includes the factors associated with the operation of the piezoelectric actuator, such as the needle stroke, rise time, open time, cooling temperature, and the other includes the factors for the dispensing equipment, such as the syringe pneumatic pressure, nozzle diameter, nozzle temperature, and so on. As a first step, in order to evaluate these factors at practical operating conditions, four parameters that are directly related to the piezoelectric actuators are selected in this work. In the proposed non-contact jetting dispenser, the actuating characteristics of the piezoelectric actuators are extremely important to achieve high jetting performance. It is assumed that each parameter displays two levels, and the operating parameter combinations are listed in Table 4. The two levels of each parameter were determined from the following criteria that are frequently considered in practical working conditions.