mi14061267.pdf - 第12页
Micromachines 2023 , 14 , 1267 12 of 17 can be reached; that is, the device proposed in this work has both high efficiency and high precision. 4. Experiment T est In the above section, the basic mechanism of micro-droplet…
Micromachines 2023, 14, 1267 11 of 17
Micromachines 2023, 14, x FOR PEER REVIEW 19 of 28
The nozzle
diameter is 0.2mm
The nozzle diameter
is 0.25mm
The nozzle
diameter is 0.3mm
The nozzle diameter
is 0.35mm
The nozzle
diameter is 0.4mm
0.454T
0.467T
0.537T
0.6572T 0.682T
1.50 3×10
1
0
1.33 6×10
1
1.16 9×10
1
1.00 2×10
1
8.35 1
6.68 1
5.01 0
3.34 0
1.67 0
1.67 0×10
1
1.33 3×10
1
0
1.18 5×10
1
1.03 7×10
1
8.88 5
7.40 4
5.923
4.442
2.962
1.48 1
1.48 1×10
1
1.052×10
1
0
9.34 8
8.180
7.011
5.843
4.67 4
3.506
2.337
1.16 9
1.16 9×10
1
7.01 5
0
6.235
5.45 6
4.67 6
3.89 7
3.118
2.33 8
1.559
7.79 4
7.794×10
-1
4.99 2
0
4.437
3.88 2
3.32 8
2.77 3
2.218
1.66 4
1.109
5.54 6
5.546×10
-1
Figure 18. The change in droplet outlet velocity caused by the change in nozzle diameter.
Figure 18. The change in droplet outlet velocity caused by the change in nozzle diameter.
Micromachines 2023, 14, x FOR PEER REVIEW 20 of 28
0 0.00005 0.0001 0.00015 0.0002 0.00025 0.0003 0.00035
0
Droplet volume [ L ]
Time [ s ]
0.2mm
0.25mm
0.3mm
0.35mm
0.4mm
8
410
−
×
8
310
−
×
8
210
−
×
8
110
−
×
8
110
−
−×
Figure 19. The change in the volume of droplets ejected caused by the change in nozzle diameter.
Based on the above simulation analysis, it can be seen that the frequency adjustment
in a small range has lile influence on the injection performance of the piezoelectric micro-
jet device. In order to reduce the difficulty of injection, improve the injection efficiency
and increase the droplet outlet velocity and volume, the following aspects can be consid-
ered: increasing the voltage amplitude of the input signal, reducing the nozzle diameter
and using low viscosity oil. If the main consideration is to improve the accuracy of droplet
control, we can try to reduce the voltage amplitude of the input signal, increase the nozzle
diameter and use high-viscosity oil. The voltage amplitude and the nozzle diameter have
significant influences on the droplet injection performance, while the oil viscosity has little
influence on the droplet volume, namely the control accuracy, when it is greater than 100
Pa.s. However, as the viscosity of the oil increases, the difficulty of droplet injection increases
and the outlet velocity decreases. Therefore, the piezoelectric micro-jet device is more suit-
able for ejecting droplets below 100 Pa.s. In the above simulation analysis, the micro-jet de-
vice can achieve the highest accuracy of 15.53 nL with a nozzle diameter of 0.2 mm. Under
the voltage amplitude of 200 V, the maximum injection volume of 82.21 nL can be reached;
that is, the device proposed in this work has both high efficiency and high precision.
4. Experiment Test
In the above section, the basic mechanism of micro-droplet injection is explained
through ANSYS two-phase, two-way fluid–structure coupling analysis, and the influence
of various parameters on the device′s injection performance is analyzed. In this section,
an experimental system will be set up to shoot micro-droplet injection videos with indus-
trial cameras to further verify the feasibility of the proposed device.
In order to verify the feasibility of the proposed device, the experimental system is
built, as shown in Figure 20. The experimental system mainly consists of a prototype, a
personal computer (PC), a signal generator (DG4162, RIGOL, Beijing, China), a power am-
plifier (ATA-4051, Aigtek Inc., Xi’an, China) and an industrial camera. The experimental
steps are as follows: firstly, the prototype is injected with a certain viscosity of viscosity
lubrication oil; then, a given square wave signal is applied in the prototype through the
signal generator and power amplifier, and then, the industrial camera is started to record
the injection process. Finally, the video taken with the industrial camera is exported and
analyzed using the PC.
Figure 19. The change in the volume of droplets ejected caused by the change in nozzle diameter.
Based on the above simulation analysis, it can be seen that the frequency adjustment in
a small range has little influence on the injection performance of the piezoelectric micro-jet
device. In order to reduce the difficulty of injection, improve the injection efficiency and
increase the droplet outlet velocity and volume, the following aspects can be considered:
increasing the voltage amplitude of the input signal, reducing the nozzle diameter and
using low viscosity oil. If the main consideration is to improve the accuracy of droplet
control, we can try to reduce the voltage amplitude of the input signal, increase the nozzle
diameter and use high-viscosity oil. The voltage amplitude and the nozzle diameter have
significant influences on the droplet injection performance, while the oil viscosity has
little influence on the droplet volume, namely the control accuracy, when it is greater than
100 Pa.s. However, as the viscosity of the oil increases, the difficulty of droplet injection
increases and the outlet velocity decreases. Therefore, the piezoelectric micro-jet device is
more suitable for ejecting droplets below 100 Pa.s. In the above simulation analysis, the
micro-jet device can achieve the highest accuracy of 15.53 nL with a nozzle diameter of
0.2 mm. Under the voltage amplitude of 200 V, the maximum injection volume of 82.21 nL
Micromachines 2023, 14, 1267 12 of 17
can be reached; that is, the device proposed in this work has both high efficiency and high
precision.
4. Experiment Test
In the above section, the basic mechanism of micro-droplet injection is explained
through ANSYS two-phase, two-way fluid–structure coupling analysis, and the influence
of various parameters on the device
0
s injection performance is analyzed. In this section, an
experimental system will be set up to shoot micro-droplet injection videos with industrial
cameras to further verify the feasibility of the proposed device.
In order to verify the feasibility of the proposed device, the experimental system is
built, as shown in Figure 20. The experimental system mainly consists of a prototype, a
personal computer (PC), a signal generator (DG4162, RIGOL, Beijing, China), a power
amplifier (ATA-4051, Aigtek Inc., Xi’an, China) and an industrial camera. The experimental
steps are as follows: firstly, the prototype is injected with a certain viscosity of viscosity
lubrication oil; then, a given square wave signal is applied in the prototype through the
signal generator and power amplifier, and then, the industrial camera is started to record
the injection process. Finally, the video taken with the industrial camera is exported and
analyzed using the PC.
Micromachines 2023, 14, x FOR PEER REVIEW 21 of 28
PC
Prototype
Industrial
camera
Signal generator
Power amplifier
Figure 20. The experimental system.
Figure 20. The experimental system.
Corresponding to the above simulation analysis, the experimental parameters are
set as follows: voltage amplitude, 100 V; square wave signal frequency, 728 Hz; nozzle
diameter, 0.4 mm; fluid viscosity, 200 Pa.s. The results of the injection experiment are shown
in Figure 21. Figure 21a shows the state of the piezoelectric micro-jet device when it is not
working, and Figure 21b–d are the injection diagrams of the piezoelectric micro-jet device
after the given square wave signal is applied. Figure 21b–d, respectively, correspond to the
droplet just being squeezed out of the nozzle, the droplet separating from the oil and being
ejected and forming satellite droplets, which are in accordance with the simulation in the
above section, further verifying the correctness of the injection mechanism revealed. It can
be seen from the observation that after the device works, the size of the droplets ejected
is uniform and the injection state is stable, which can realize long-term continuous and
stable injection, which confirms the correctness of the piezoelectric micro-jet principle and
the feasibility of the proposed piezoelectric micro-jet device. The experimental video is
attached as Video S1.
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Micromachines 2023, 14, x FOR PEER REVIEW 22 of 28
Corresponding to the above simulation analysis, the experimental parameters are set
as follows: voltage amplitude, 100 V; square wave signal frequency, 728 Hz; nozzle diam-
eter, 0.4 mm; fluid viscosity, 200 Pa.s. The results of the injection experiment are shown in
Figure 21. Figure 21a shows the state of the piezoelectric micro-jet device when it is not
working, and Figure 21b–d are the injection diagrams of the piezoelectric micro-jet device
after the given square wave signal is applied. Figure 21b–d, respectively, correspond to
the droplet just being squeezed out of the nozzle, the droplet separating from the oil and
being ejected and forming satellite droplets, which are in accordance with the simulation
in the above section, further verifying the correctness of the injection mechanism revealed.
It can be seen from the observation that after the device works, the size of the droplets
ejected is uniform and the injection state is stable, which can realize long-term continuous
and stable injection, which confirms the correctness of the piezoelectric micro-jet principle
and the feasibility of the proposed piezoelectric micro-jet device. The experimental video
is aached as Video S1.
When the device is
not working
When the device is applied a given square wave signal
a
b
cd
Figure 21. The results of the injection experiment: (a) The state of the piezoelectric micro-jet device
when it is not working; (b) the droplet just being squeezed out of the nozzle; (c) the droplet sepa-
rating from the oil and being ejected; (d) the formation of satellite droplets.
In this work, the verification experiment is carried out according to the simulation
content in the previous part. The main research is to investigate the outlet velocity and
droplet volume of the piezoelectric micro-jet device under different voltage amplitudes,
signal frequencies, oil viscosities and nozzle diameters. The standard experimental condi-
tions are set as follows: voltage amplitude, 100 V; signal frequency, 8090 Hz; nozzle diam-
eter, 0.4 mm; oil viscosity, 200 Pa.s. The experimental results of the effects of voltage am-
plitude, signal frequency, oil viscosity and nozzle diameter on droplet outlet velocity
when other experimental conditions remain unchanged are shown in Figure 22. The ex-
perimental results are consistent with the simulation results in the above part, and the
errors are all within the acceptable range. The maximum error of Figure 22a–d is 11.93%,
11.53%, 8.797% and 11.55%, respectively. The experimental results of the effects of voltage
amplitude, signal frequency, oil viscosity and nozzle diameter on droplet volume when
other experimental conditions remain unchanged are shown in Figure 23. The experi-
mental results are consistent with the simulation results in the above section, and the er-
rors are all within the acceptable range. The maximum error in Figure 23a–d is 12.17%,
6.92%, 4.86% and 9.61%, respectively.
Figure 21.
The results of the injection experiment: (
a
) The state of the piezoelectric micro-jet device
when it is not working; (
b
) the droplet just being squeezed out of the nozzle; (
c
) the droplet separating
from the oil and being ejected; (d) the formation of satellite droplets.
In this work, the verification experiment is carried out according to the simulation
content in the previous part. The main research is to investigate the outlet velocity and
droplet volume of the piezoelectric micro-jet device under different voltage amplitudes,
signal frequencies, oil viscosities and nozzle diameters. The standard experimental con-
ditions are set as follows: voltage amplitude, 100 V; signal frequency, 8090 Hz; nozzle
diameter, 0.4 mm; oil viscosity, 200 Pa.s. The experimental results of the effects of voltage
amplitude, signal frequency, oil viscosity and nozzle diameter on droplet outlet velocity
when other experimental conditions remain unchanged are shown in Figure 22. The ex-
perimental results are consistent with the simulation results in the above part, and the
errors are all within the acceptable range. The maximum error of Figure 22a–d is 11.93%,
11.53%, 8.797% and 11.55%, respectively. The experimental results of the effects of voltage
amplitude, signal frequency, oil viscosity and nozzle diameter on droplet volume when
other experimental conditions remain unchanged are shown in Figure 23. The experimental
results are consistent with the simulation results in the above section, and the errors are all
within the acceptable range. The maximum error in Figure 23a–d is 12.17%, 6.92%, 4.86%
and 9.61%, respectively.
Micromachines 2023, 14, x FOR PEER REVIEW 23 of 28
50 100 150 200
0
5
10
15
20
25
30
35
Velocity (m/s)
Voltage amplitude (V)
7900 8000 8100 8200 8300
5.0
5.2
5.4
5.6
5.8
6.0
6.2
Velocity ( m/s)
Signal frequency (Hz)
0 50 100 150 200
4
6
8
10
12
Velocity (m/s)
Oil viscosity (cs)
0.2 0.3 0.4
5
10
15
20
Velocity (m/s)
Nozzle diameter (m)
Simulation result
Experimental result
a
b
c
d
Simulation result
Exp erimental result
Simulation result
Experimental result
Simulation result
Experimental result
Figure 22. The experimental results of voltage amplitude, signal frequency, oil viscosity and nozzle
diameter on droplet outlet velocity: (a) The experimental results of voltage amplitude on droplet
outlet velocity; (b) the experimental results of signal frequency on droplet outlet velocity; (c) the
experimental results of oil viscosity on droplet outlet velocity; (d) the experimental results of nozzle
diameter on droplet outlet velocity.
Figure 22.
The experimental results of voltage amplitude, signal frequency, oil viscosity and nozzle
diameter on droplet outlet velocity: (
a
) The experimental results of voltage amplitude on droplet
outlet velocity; (
b
) the experimental results of signal frequency on droplet outlet velocity; (
c
) the
experimental results of oil viscosity on droplet outlet velocity; (
d
) the experimental results of nozzle
diameter on droplet outlet velocity.