Application Cases

Experiment Title: Application of High-Voltage Amplifier in Experimental Research on Actuation of Gallium-Based Liquid Metal Micro-Motors

Research Direction: Novel Materials

Test Objective:
Although micro/nano motors are power devices based on practical applications, their value in scientific research is particularly significant. At the micro/nanoscale, they can accept energy input, perform energy conversion and mechanical work output, and achieve specific mechanical functions. Research on them brings together electronics, mechanics, materials science, and emerging interdisciplinary micro- and nano-scale technologies from physics, chemistry, and biology. This is of great importance for studying the motion characteristics of particles at the micro/nano scale, and in turn, it promotes the development of physics, chemistry, and materials science.

Testing Equipment:
ATA-2082 high-voltage amplifier, chip, printed circuit board (PCB), Android phone, computer, small copper microbeads, etc.

Figure 4-5 (a) Schematic diagram of the control platform. (b) Three-dimensional motion trajectory of the gallium-based liquid metal micro-motor guided by a programmed electric field. (c) Photographic image of the 4×4 array operating chip composed of ~800 μm microbeads. (d) Schematic diagram of the "mini piano". (e) Photographic image of manipulating the gallium-based liquid metal micro-motor to jump while playing music.

Experimental Procedure:
A control platform was designed to achieve point-to-point precise manipulation of the gallium-based liquid metal micro-motor. The motor control platform system consists of an interactive media terminal for inputting commands, a power terminal for generating analog signals, a voltage amplifier terminal for signal amplification, and an operating chip for receiving the amplified signals, as shown in Figure 4-5(a). The interactive media terminal for inputting commands is primarily composed of a computer pre-installed with a command program. A predefined command signal string is set within the command program. This signal string is converted into an analog signal by a power converter. The analog signal is then amplified by the voltage amplifier, and the amplified signal pulses are transmitted to the operating chip. Consequently, the motor executes three-dimensional jumping motions along a predetermined trajectory according to the predefined command signal string.

The operating chip is fabricated by micro-welding small copper microbeads with a diameter of 800 μm onto a printed circuit board (PCB) with a pre-designed circuit structure. The PCB size is 5 cm × 5 cm, with 4×4 micro-grooves designed inside, each with a diameter of 200 μm. The small copper beads are welded into the 4×4 micro-grooves using micro-welding technology. The operating chip is thus completed, as shown in Figure 4-5(c).

The micro-motor control platform consists of the operating chip with a 4×4 array of 800 μm diameter copper microbeads and a paper-based substrate. The distance between the operating chip and the paper-based substrate is 2 mm. By independently switching the signal pulses applied to each micro-copper ball in the 4×4 matrix, three-dimensional jumping motions between different microballs are achieved, enabling precise and controllable movement of the micro-motor. Using this control system, we successfully realized the motor's three-dimensional precise jumping task along fixed trajectories (the four letter trajectories "C", "T", "G", and "U") on the paper-based substrate.

The operation process is as follows: First, pulse signals corresponding to the "C", "T", "G", and "U" trajectories are sequentially input to the 4×4 matrix micro-copper balls on the operating chip at time intervals of 1 second. The motor then follows the local electric fields provided by the microelectrodes at different time intervals to perform three-dimensional jumps along the specified horizontal directions. It is noteworthy that the distance between adjacent microbeads must be at least greater than the radius of the beads to prevent arcing (sparks) when strong signals are applied. By applying pre-set voltage trajectories to the electrode array, the gallium-based liquid metal micro-motor can jump along the specified path and can also be started/stopped as needed, as shown in Figure 4-5(b).

Obviously, in this control system, the precision of operation largely depends on the size of the array units. By reducing the diameter of the microbeads and the spacing between them, a high precision of up to 10 micrometers can be achieved. However, when the unit size is further reduced, the electric field generated by the microelectrodes also decreases correspondingly, which greatly affects the jumping performance of the gallium-based liquid metal. Therefore, it is necessary to evaluate the balance between operational precision and performance in each specific case.

Based on this, we designed and fabricated a "mini electronic piano", as shown in Figure 4-5(d). The "mini electronic piano" system consists of an Android phone with a piano application installed, a central computer, a voltage source, and a control platform. The Android phone with the piano application serves as the input command port for playing musical notes. The central computer connected to the phone port is used as a receiver for these signals, converting the input musical note signals into electrical signals. The electrical signals are converted into signal pulses by the voltage source and finally transmitted to the control platform.

The control platform system consists of two parts: the operating chip and the touch-sensitive pressure-sensing substrate system. The operating chip is composed of a PCB with a pre-designed circuit structure and small copper microbeads with a diameter of 800 μm. The PCB size is 2.5 cm × 7 cm, with 2×7 micro-grooves designed inside, each with a diameter of 200 μm. The small copper beads are welded into the 2×7 micro-grooves using micro-welding technology. Each micro-welded small copper bead is connected in parallel with the circuit on the PCB, and the circuit board is connected to the voltage source.

The touch-sensitive pressure-sensing substrate system consists of two parts: the front part is a paper-based substrate, and the rear part is a touch-sensitive pressure-sensing film, as shown in Figure 4-4. The touch-sensitive pressure-sensing film is connected to a signal converter, which converts pressure signals into electrical signals. The other end of the signal converter is connected to audio equipment that can receive electrical signals and convert different electrical signals into different musical notes. Thus, the touch-sensitive pressure-sensing substrate system is completed. The distance between the operating chip and the pressure-sensing substrate system is 2 mm. The three-dimensional motion of the gallium-based liquid metal is recorded by a CCD camera. The operating chip consists of a 2×7 microelectrode array, divided into 7 parts along the X-axis, encoded with notes from "C5" to "B5" (Figure 4-5(e)).

Figure 4-4: Touch-sensitive pressure-sensing substrate

Experimental Results:
When a key, such as "C4", is pressed on the mobile phone piano system, the input command is transmitted via the phone to the central computer. The central computer program converts the signal corresponding to that key into an electrical signal, which is then sent to the voltage source to be converted into a pulse signal. The pulse signal is transmitted to the microelectrode at the front end above the "C4" position on the operating chip. At this moment, the local electric field generated by the microelectrode guides the micro-motor to perform in-situ three-dimensional motion. After jumping for 2 seconds, the delay circuit on the operating chip transmits the pulse signal to the next microelectrode, causing the local electric field at the previous microelectrode to disappear and generating a local electric field at the next microelectrode. This pulls the micro-motor to jump between the rear microelectrode and the touch-sensitive pressure-sensing substrate.

The touch-sensitive pressure-sensing substrate senses the pressure exerted on its bottom surface during the motor's jumping process and transmits a pressure signal to the signal converter. The signal converter converts the pressure signal into an electrical signal and transmits it to the audio equipment, which converts the electrical signal into the corresponding musical note. The audio equipment then emits the note corresponding to the input command, as if we are manipulating the gallium-based metal micro-motor to play the piano.

Aigtek ATA-2082 High-Voltage Amplifier:

Figure: ATA-2082 High-Voltage Amplifier Specifications and Parameters