To evaluate the pump performance, the pump was excited in the 3-, 4- and 6-phase peristaltic motions, and actuated with the step-function signals with varied phase frequencies created by the phase controller. What fascinates me about output performance is the frequency domain. Two 0.04 inch ID tubes were connected to the inlet and outlet of the peristaltic micropump.The outlet tube was placed into a reservoir on a scale. The pumping rates were calculated over a period of time from the weight of deionized water (DI water) or blood, measured by the scale. The maximum displacement of the moving diaphragm with DI water was measured by fiber-optical measurement system (MTI Instruments, MTI 2000).The fiber-optical measurement system served as a displacement sensor, monitoring the dynamic performance of the pump. The signals from the fiber-optical measurement system were recorded using a digital oscilloscope.
Experimental results indicate that bidirectional flow could be achieved by reversing the actuation sequence.
T T h h e e D D a a m m p p i i ng n g E E f f f f e e c c t t s s o o n n P P u u m m p p D D i i a a p p h h r r a a g g m m
A. The Phase sequence and frequency shift
Fig. 33 Displacement of the middle moving diaphragm as a function of phase frequency at 100 Vpp(4P16)
Figure 34 shows the displacement of the middle moving diaphragm as a function of phase frequency at 100 Vpp for the 3-, 4- and 6-phase sequences. The figure indicates that different actuation sequences resulted in different resonant frequencies of the diaphragm. Using Eq. (2.44), (2.45), we can make sense of the reason why the resonant frequency shift in 3-phase sequence has a stronger tendency compared to the other two driving sequences. The
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0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
100Vpp - PZT M 4 Phase 6 Phase 3 Phase
Displacement ( μ m)
Frequency (Hz)
experimental displacement frequency-response curves at different phase motion (as shown in Fig. 34.) have the comparable results with the presented theoretic analysis. The resonant frequencies of the diaphragm for the 3-, 4- and 6-phase sequences were 100Hz, 150Hz and 200Hz, respectively. The maximum displacement of the diaphragm for the 3-, 4- and 6-phase actuation sequences was 3.7μm, 4.0μm and 3.8μm (peak-to-peak), respectively.
Fig. 34 Flow rate vs. phase frequency at 100 Vpp
Figure 35 illustrates the flow rates of the micropump at an applied voltage of 100Vpp with a phase frequency range of 50–1000Hz for the 3-, 4- and 6-phase peristaltic motions. The maximum flow rates of the 3-, 4- and 6-phase sequences occurred at
400Hz, 500Hz and 700Hz, and were 21.4μl/min, 34.6μl/min and 36.8μl/min, respectively. The same observation compared with Fig.34 applies to flow rate frequency-response curves. The frequency of resonance peak: 6-phase >4-phase >3-phase. According to Fig. 35, the flow rates peaked at a certain frequency and fell at higher frequencies for all actuation sequences. The experimental results clearly indicate that the pumping rates rose with increasing frequency at lower frequencies. The moving diaphragm was not fast enough to keep up with the actuation signal at higher frequencies, so the actuation magnitude decreased, thus reducing the pumping performance.
Fig. 35 Displacement of the middle moving diaphragm as a function of phase frequency at 100 Vpp (4P20)
3 Phase-100 Hz；4 Phase-150 Hz；6 Phase-200Hz
Fig. 36 Flow rate vs. phase frequency at 100 Vpp (4P20)
3 Phase-250 Hz；4 Phase-300 Hz；6 Phase-400Hz
3 Phase-29.4 μl/min；4 Phase-40 μl/min；6 Phase- 33.4 μl/min
Fig. 37 The displacement frequency of 2-phase sequence
The frequency of resonance peak: 6-phase >4-phase >3-phase>2-phase
B. The working fluids and frequency shift
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Fig. 38 The displacement of membrane versus the driving frequency at 100 V (4P10)
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10 20 30 40 50 60 70
Flow rate [
μl/min]
Frequency [Hz]
DI water Blood
Fig. 39 The Flow rate of pumping versus the driving frequency at 100 V (4P10)
Fig. 40 The displacement of diaphragm versus the driving frequency for different working fluids.
Three kinds of working fluids were tested by diffuser/nozzle micropump: water, insulin and blood. Fig. 40 shows the displacement of the membrane for DI water, insulin and blood at the driving voltage of 10 V and frequency varied from 200 Hz to 1 KHz.
The resonance frequencies for DI water, insulin and whole blood are 500 Hz, 350 Hz and 350 Hz, respectively. The resonance frequencies for insulin and blood are much lower than that for DI water. This results from the higher viscosity and density of the insulin and blood.
According to Fig. 40, it can be seen that the resonance frequency of the pump is strongly dependent on the fluid properties.
C. The chamber height and frequency shift
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Fig. 41 The 3-phase sequence displacement frequency
response versus the chamber height.
The pump can be design for gas pumping. For higher expansion/compression ratio, we design the chamber height 10μm
4 0 2 0 2
Therefore, the damping constant c is proportional to 3
0
1 h .
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Fig. 42 The 4-phase sequence displacement frequency response versus the chamber height.
4P18-140Hz, 4P20-160Hz
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Fig. 43 The 6-phase sequence displacement frequency response versus the chamber height.
4P18-220Hz, 4P20-230Hz
1. The driving single connected to three chambers
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0.20 700 Hz PZT-left
PZT-middle
Fig. 44 4-phase three chambers driving 2. The driving single connected to just the middle chamber
0 200 400 600 800 1000 chambers or just the middle chamber can affect the amplitude of the displacement frequency response without affecting their stiffness.
T T he h e I I m m p p r r o o v v e e m m e e nt n t f f o o r r D D r r i i v v i i n n g g C C i i r r c c u u i i t t
A. Improvement of the rise time for the differential
amplifier
R1
R5 R2
VCC
VCC
6 R3
4
0 2 PZT
3
1 5
Signal+ Signal-
Fig. 46 The charging and discharging loop of the differential amplifier
Fig.46 indicates the charging and discharging loop of the differential amplifier. The product R C is called the "time constant", and is a characteristic quantity of the differential amplifier. The RC product can be used to determine the voltage to which any capacitor will charge through any resistance, over any period of time, towards any source voltage. The rise time will be decrease and maintain the square shape by reducing the collector resistors of the differential amplifier. The following is the testing of reducing the collector resistors in the differential amplifier to investigate the displacement (measured on the middle chamber) and flow rate.
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Fig. 47 The displacement vs. frequency in 3-phase sequence by reducing the collector resistance from 50 K to 10 K Ohm
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Fig. 48 The flow rate vs. frequency in 3-phase sequence by reducing the collector resistance from 50 K to 10 K Ohm
0 100 200 300 400 500 600
Fig. 49 The displacement vs. frequency in 4-phase sequence by reducing the collector resistance from 50 K to 10 K Ohm
0 100 200 300 400 500 600
Fig. 50 The flow rate vs. frequency in 4-phase sequence by reducing the collector resistance from 50 K to 10 K Ohm
0 100 200 300 400 500 600
Fig. 51 The displacement vs. frequency in 6-phase sequence by reducing the collector resistance from 50 K to 10 K Ohm
0 100 200 300 400 500 600
Fig. 52 The flow rate vs. frequency in 6-phase sequence by reducing the collector resistance from 50 K to 10 K Ohm
From the above observation, we know reducing the resistance at the collectors will make the displacement of the diaphragm and flow rate to increase, in 3, 4, and 6-phase sequence,
B. Pump performance with offset driving voltage
We determined three differential situations which were the offsetting voltage upward from +80 V to -20 V, the offsetting voltage downward from +20 V to -80 V, and the voltage from +50 V to -50 V in transporting two fluids, air and DI water.
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0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20
Displacement
Frequency
air, (+50,-50) air, offset(+80,-20) water,(+50,-50) water, offset(-80,+20)
Fig. 53 The displacement vs. frequency operated in +80 V to -20 V, +50 V to -50 V and +20 V to -80 V deferential outputs
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4 6 8 10 12 14 16 18 20 22
Flow rate
Frequency
water, (-50,+50) water, offset(+80,-20) water, offset(-80,+20)
Fig. 54 The flow rate vs. frequency operated in +80 V to -20 V, +50 V to -50 V and +20 V to -80 V deferential outputs