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Supplementary Materials

Guoqing Zhao1, Shuyu Chen1, Weijia Wen1, Fumiaki Miyamaru2, Mitsuo W. Takeda2,

Jianding Yu3 and Ping Sheng1

1Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.

2Department of Physics, Faculty of Science, Shinshu University, Matsumoto 390-8621, Japan

3Japan Aerosp Explorat Agcy, ISS Sci Project Off, Sagamihara, Kanagawa 2298510 Japan

A highly sensitive electrorheometer is specially designed for measuring ER effect

in microgravity environment. It is required that the rheometer can be operated fully

automatically and remotely, survive the large impact force (>10G) and strong vibration

in the breaking zoon, and fit the limited space of the drop capsule. An imaging system

should be integrated. The system should not be interfered by the noise from the

surrounding electronics. It was noted at the lab testing period that the noise interference

was very strong due to our highly integrated design. We carefully employed shield

technology, ground technology and filter technology to solve this problem. Bellow,

technique details on our setup are provided:

1 General Information

Linear shear type rheometer is used. Setup is shown in Figure 1. The sample vessel

(3) is formed by the upper electrode plate (1), bottom electrode plate (2), and the

insulating spacer between them. The volume of the vessel is 95.8mm (L) 95.8mm (W)

1mm (H). The upper electrode is a polished aluminum plate. The bottom electrode is

made of ITO glass which also serves as the observation window for the CCD camera (7).

The insulating spacer is fabricated from Delrin materials. The imaging system is formed

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by CCD camera (7), optical lens (8), illuminating system (9), and data recording

notebook computer. Force sensor (5) is connected to the upper electrode through a glass

fiber, which also serves as insulator for protecting the sensor from high voltage. Motor

(4) is connected to the suspending stage (6) through a shaft. After proper adjustment, the

stage together with the bottom electrode can move smoothly at the required speed. The

force signal is sampled and recorded by experimental controller.

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Figure 1: (a) Scheme of the electrorheometer with (1) upper electrode plate, (2) bottom electrode

plate (ITO glass), (3) sample vessel, (4) motor, (5) force sensor, (6) suspending stage, (7) CCD, (8)

optical lens of imaging system, (9) illuminating system. (b), Photo of the electrorheometer.

2 Imaging Systems

USB CCD camera (Shimadzu, Moticam 2000) is used to capture the images of

micro structure formation. The frame rate of Moticam 2000 can go up to 30 FPS with

resolution of 800 600. Optical lens (Metron) is selected according to the camera and the

display to make the image magnification larger than 10, so that the 100 particles can

be clearly identified. Two notebook computers (Lenovo X200) are employed as recorder.

3. Force Sensing

Low level force sensor type 9205 (Kistler, http://www.kistler.com/) [1] and charge

amplifier type 5037B1 (Kistler) [2] as shown in Figure 2(a) and (b) are selected for the

force sensing module. Type 9205 is quartz force sensor developed by Kistler, which is

for measuring quasistatic and dynamic tensile forces with high sensitivity less than 1mN

or wide range from -50N to 50 N. It can survive an impact force less than 50N

(maximum overload: -75N to 150N). Full measurement range of charge amplifier

5037B1 is set to 150p. The sensitivity of force sensor type 9205 is set to be 115pC/N.

That means the full measurement range is 1.30N ( 150pC/115pC/N).

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Figure 2: (a) Low level force sensor type 9205. (b) Charge amplifier type 5037B1. (c) Scheme of

charge amplifier type 5037B1.

Friction force between spacer (fixed on the upper electrode) and bottom electrode

would be larger than the shear force from ER effect. So a zero operation is needed to

eliminate this friction force. Zero operation is performed immediately after microgravity

environment is established but before the electrical field is applied. So after zero

operation, only electrical field induced force is left and measured by the sensor.

Technically zero operation is done through reset operation of charge amplifier type

5037B1. As shown in Figure 2(c), the reset operation discharges the integration

capacitor CB, so the output of charge amplifier returns to zero.

4 The Control System

NI Compact RIO system shown in Figure 3 is selected as experimental controller

(programmable with Labview software and with rich choices of IO modules). The

experimental controller consistes of one controller module cRIO-9014, one chassis

module cRIO-9101 (programmable FPGA integrated), three digital I/O modules NI 9401

and one analog input module NI9229 (24bits ADC, 50 kS/sec of maximum sampling

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rate) [3]. The software for experiment sequence control and data acquisition is

programed with Labview and implemented into cRIO system.

Figure 3: Photo of the assembled NI Compact RIO system. (a) cRIO-9014 controller module, (b)

cRIO-9101 chassis module, (c) NI9229 analog input module, and (d) three NI 9401 digital I/O

modules.

5 The High Voltage Module

The electric field is applied by using rectangular waveform signal (1Hz, 50% duty

cycle) with high voltage. Rise time of pulse depends on the driving capability of the high

voltage unit, while the fall time depends more on the load of output. The provider

(Ultravolt) helped to perform a special test getting relevant parameters of the selected

high voltage unit 2C24-P20-C [4], as shown in Table 1, with the test conditions attached

below. As a compact high voltage unit, the output dynamic performance of the unit

2C24-P20-C is excellent.

Table 1: Output dynamic performance of high voltage unit 2C24-P20-C (Ultravolt).

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Output (V) Observed Rise Time (ms) Observed Fall Time (ms)

600 4.5 45

1200 4.0 40

2000 6.0 40 Test conditions: A Voltage divider (1 MΩ load) is constructed with 100kΩ, 390kΩ, 510Ω ceramic

resistors. The voltage is measured at 10:1 across the 100kΩ resistor for the measurement shots of

1200 & 2000 VDC. At 600 VDC, the voltage is measured directly.

The high voltage module shown in Figure 4(b) and (c) is fabricated in lab. Its

functions are illustrated in Figure 4(a).

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Figure 4: (a) Scheme of the high voltage module. (b) Top view of the high voltage module. (c)

Inside view of the high voltage module.

6 The Interface Module

Interface module is responsible for analog and digital signal conditioning, power

supply for circuits and other systems. The most important part is signal conditioner for

force sensing. The analog power supply is carefully designed by using a separate group

of batteries to minimize the ripple and noise. A four orders Butterworth filter with 10 Hz

cut-off frequency is utilized to filter the noise. The interface module which is shown in

Figure 5(b) and (c) is fabricated in lab. Its function is illustrated in Figure 2.7 (a).

Figure 5: (a) Function scheme of interface module. (b) Top view of interface module. (c) Inside

view of interface module.

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7 The Suspending Stage and Remote Control System

The suspending stage is driven by an AC servo motor (AC motor model

R2AA0401OFXH00, AC servo driver model RS1A01AAWXXA3POS, SANYO

DENKI) through the shaft from a micrometer (Mitutoyo).

During the experiment, all the operations should be done through remote control. A

Wi-Fi network connection is used to construct remote control system. The scheme of

remote control system is shown in Figure 6.

Figure 6: Schematic of the remote control system.

8 Experimental Setup Performance Analysis

The scheme of the whole experimental system is shown in Figure 7. A test was

performed before the experiment.

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Figure7: Scheme of the experimental system and the signal connections.

It is found that the most strong noise interference to force signal comes from the

high frequency noise generated by the AC motor and motor servo driver. This noise does

not affect functional work of digital signals, but it increases the noise level of analog

signals and the drifting of charge amplifier significantly.

After properly connected to isolate components and noise sensitive components,

and applying shielding to the noise source components, the noise returns to its original

level. And the drifting issue of charge amplifier turns to be neglectable with the short

measuring time (less than 5 seconds).

Full measurement range of charge amplifier 5037B1 is set to 150p. The sensitivity

of force sensor type 9205 is 115pC/N. That means the full measurement range is

1.30N ( 150pC/115pC/N). The output voltage range of charge amplifier 5037B1 is

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from -10V to 10V. So the force resolution of charge amplifier is 10000mV/1300mN =

7.69 mV/mN. The noise level of charge amplifier 5037B1 is up to 5mV, comparable to

its designed resolution. The noise level can be decreased though adding a four orders

Butterworth filter between output of charge amplifier and ADC. This filter is also used

for filtering interference noise. The final noise level goes down to around 2 mV.

References:

[1] Datasheet of low level force sensor type 9205. www.kistler.com/.

[2] Datasheet of charge amplifier type 5307B. www.kistler.com/.

[3] Operating instructions and specifications NI 9229. www.ni.com.

[4] Ultravolt Product Catalog. www.ultravolt.com.

Electronic Supplementary Material (ESI) for Soft MatterThis journal is © The Royal Society of Chemistry 2011

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