2023.09.08
Solution of Precise Control of Vacuum in Liquid Thickness Adjustment of Liquid Phase Transmission Electron Microscope
SHARE
MORE DETAIL
1. Why Proportional Pressure Regulator can apply on electron microscope?
In recent years, liquid-phase transmission electron microscopy technology based on transmission electron microscopy, micro-nano processing and thin film manufacturing technology has been used to build micro-experimental platforms at various nanometer resolution scales and develop new nano-characterization technologies and related fields in many fields. A standard liquid cell is a silicon microchip with two electronically transparent silicon nitride (SiN) film windows supported by an isolation material, and the liquid sample is filled between the two windows.
Theoretically, the liquid thickness can be set by spacers between microchips, but in actual observation, the microchips need to be placed in an ultra-high vacuum environment of a transmission electron microscope, causing the pressure inside and outside the membrane window to be different. The difference will cause the membrane window to deform and expand, causing the liquid thickness to change, and this change often exceeds several times.
Therefore, unless bubbles are generated, this thickness change will seriously affect the resolution of the observations. In addition, pillars can be used to connect the top and bottom membrane windows to minimize expansion, but this kind of liquid pool with a fixed thickness cannot be loaded with different samples for observation, which is not universal and applicable.
Theoretically, the liquid thickness can be set by spacers between microchips, but in actual observation, the microchips need to be placed in an ultra-high vacuum environment of a transmission electron microscope, causing the pressure inside and outside the membrane window to be different. The difference will cause the membrane window to deform and expand, causing the liquid thickness to change, and this change often exceeds several times.
Therefore, unless bubbles are generated, this thickness change will seriously affect the resolution of the observations. In addition, pillars can be used to connect the top and bottom membrane windows to minimize expansion, but this kind of liquid pool with a fixed thickness cannot be loaded with different samples for observation, which is not universal and applicable.
In order to reach the adjustable thickness of liquid sample in liquid phase electron microscope, it is necessary to try to precisely control the pressure difference between the inside and outside of the membrane window of the liquid pool.
This article will propose corresponding solutions for vacuum degree control inside the liquid pool. The high-precision control of the vacuum degree will adopt the dynamic balance method, which can achieve a control accuracy of ±1% under any vacuum degree within the range of 0.1~100kPa and can reach precise adjustable and constant control of liquid sample thickness.
.png)
2. Solution
The solution described in this article also uses the above-mentioned dynamic balance method to control the vacuum degree of liquid samples. The difference is that it is further refined and a specific implementation plan and detailed description of the engineering are given.
The need for thickness adjustment, while the vacuum degree control accuracy is required to be better than ±1%. The device is shown in Figure2.
.png)
The vacuum control system used to adjust the thickness of liquid samples in a liquid phase electron microscope shown in Figure 2 mainly includes a vacuum gauge, KaoLu’s Proportional Pressure Regulator, a vacuum pump, a vacuum pressure controller, a computer and its software. Their respective functions and details are described as follows:
(1) Vacuum gauge: used to precisely measure the vacuum degree of liquid samples. The vacuum gauge adopts a thin-film capacitor vacuum gauge with high measurement accuracy. In order to meet the needs of full-scale vacuum measurement, two vacuum gauges with different ranges are equipped.
(2) KaoLu’s Proportional Pressure Regulator: used to precisely adjust the intake and exhaust flow. KaoLu’s Proportional Pressure Regulator is a high-speed needle valve driven by a stepper motor. It can precisely and quickly adjust the needle valve opening in less than 1 second through an analog voltage signal of 0~10V to achieve high-precision flow adjustment.
It is very suitable for small businesses. Vacuum control within a dimensional space. Equipped with KaoLu’s Proportional Pressure Regulator to adjust the intake and exhaust flow respectively to reach high-precision control of vacuum degree.
(3) Vacuum pump: used as a vacuum source. As the vacuum source, a low-pollution dry vacuum pump is generally used to reduce the impact of vibration and noise on the entire transmission electron microscope.
(4) Vacuum pressure controller: It is used to receive the measurement signal of vacuum gauge, and automatically control KaoLu’s Proportional Pressure Regulator according to the set value of vacuum degree by PID, so that the vacuum degree of liquid sample can quickly reach set value and keep it constant for a long time.
For high vacuum degree control in the range of 0.1~1kPa, the controller needs to collect the signal of the vacuum gauge 1 with a range of 10Torr, and at the same time fix the electronic needle valve for exhaust to the fully open state.
For low vacuum degree control in the range of 1~100kPa, the controller needs to collect the signal of vacuum gauge 2 with a range of 1000Torr, and at the same time fix KaoLu’s Proportional Pressure Regulator for air intake at a certain opening state, and the controller controls KaoLu’s Proportional Pressure Regulator for exhaust.
(5) Computer and software: The computer is used to communicate with the vacuum pressure controller, and the computer software can perform various parameter settings, operation control, and digital display, graphic display, and storage of process parameters on the vacuum pressure controller through the interface.
Although the vacuum pressure controller can be used alone to control the vacuum degree, it requires manual operation through the buttons on the controller, which is complicated. However, operating the controller through computer software is more intuitive and simple.
In order to meet the high-precision requirements of liquid thickness adjustment and control, the main technical indicators of the above key components are as follows:
(1) Vacuum gauge: Thin film capacitor vacuum gauge, with measuring ranges of 10Torr and 1000Torr respectively. The accuracy of any vacuum measurement value is 0.25%.
(2) KaoLu’s Proportional Pressure Regulator: driven by a stepper motor, the control signal is an analog voltage or current signal, the full response time from fully closed to fully open is less than 1s, the repeatability is better than ±0.1%, and the valve core is corrosion-resistant.
(3) Vacuum pressure controller: 24-bit AD, 16-bit DA, 0.01% minimum output percentage, PID parameters with self-tuning function, RS 485 communication and standard MODBUS communication protocol, equipped with computer control software.
4. Conclusion
Liquid-phase transmission electron microscopy has become a basic technique for real-time monitoring of nanomaterial processes in liquids. Due to the pressure difference between the liquid and the high vacuum of the transmission electron microscope, the silicon nitride membrane window is usually bent, which can be adjusted by adjusting the liquid pool. Vacuum pressure is used to dynamically adjust the liquid thickness, resulting in an ultra-thin liquid layer in the central window region for high-resolution imaging.
Through the solution proposed in this article, an independent vacuum degree control device can be built for automatic adjustment and constant control of various thicknesses of microchip liquid samples in liquid transmission electron microscopy, and can achieve high control accuracy.
In addition, the high-precision automatic vacuum control inside the liquid pool also provides the possibility for the dynamic change of the liquid thickness in a programmed manner, which is very conducive to overcoming diffusion limitations and achieving bulk dissolution conditions.
In summary, the solution provides a fundamental method for measuring and dynamically adjusting liquid thickness in liquid-phase transmission electron microscopy experiments, enabling new experimental designs and better control of solution chemistry.
More information about KaoLu's Proportional Pressure Regulator, please visit our website!
In recent years, liquid-phase transmission electron microscopy technology based on transmission electron microscopy, micro-nano processing and thin film manufacturing technology has been used to build micro-experimental platforms at various nanometer resolution scales and develop new nano-characterization technologies and related fields in many fields. A standard liquid cell is a silicon microchip with two electronically transparent silicon nitride (SiN) film windows supported by an isolation material, and the liquid sample is filled between the two windows.
Theoretically, the liquid thickness can be set by spacers between microchips, but in actual observation, the microchips need to be placed in an ultra-high vacuum environment of a transmission electron microscope, causing the pressure inside and outside the membrane window to be different. The difference will cause the membrane window to deform and expand, causing the liquid thickness to change, and this change often exceeds several times.
Therefore, unless bubbles are generated, this thickness change will seriously affect the resolution of the observations. In addition, pillars can be used to connect the top and bottom membrane windows to minimize expansion, but this kind of liquid pool with a fixed thickness cannot be loaded with different samples for observation, which is not universal and applicable.
Theoretically, the liquid thickness can be set by spacers between microchips, but in actual observation, the microchips need to be placed in an ultra-high vacuum environment of a transmission electron microscope, causing the pressure inside and outside the membrane window to be different. The difference will cause the membrane window to deform and expand, causing the liquid thickness to change, and this change often exceeds several times.
Therefore, unless bubbles are generated, this thickness change will seriously affect the resolution of the observations. In addition, pillars can be used to connect the top and bottom membrane windows to minimize expansion, but this kind of liquid pool with a fixed thickness cannot be loaded with different samples for observation, which is not universal and applicable.
In order to reach the adjustable thickness of liquid sample in liquid phase electron microscope, it is necessary to try to precisely control the pressure difference between the inside and outside of the membrane window of the liquid pool.
This article will propose corresponding solutions for vacuum degree control inside the liquid pool. The high-precision control of the vacuum degree will adopt the dynamic balance method, which can achieve a control accuracy of ±1% under any vacuum degree within the range of 0.1~100kPa and can reach precise adjustable and constant control of liquid sample thickness.
2. Solution
The solution described in this article also uses the above-mentioned dynamic balance method to control the vacuum degree of liquid samples. The difference is that it is further refined and a specific implementation plan and detailed description of the engineering are given.
The need for thickness adjustment, while the vacuum degree control accuracy is required to be better than ±1%. The device is shown in Figure2.
The vacuum control system used to adjust the thickness of liquid samples in a liquid phase electron microscope shown in Figure 2 mainly includes a vacuum gauge, KaoLu’s Proportional Pressure Regulator, a vacuum pump, a vacuum pressure controller, a computer and its software. Their respective functions and details are described as follows:
(1) Vacuum gauge: used to precisely measure the vacuum degree of liquid samples. The vacuum gauge adopts a thin-film capacitor vacuum gauge with high measurement accuracy. In order to meet the needs of full-scale vacuum measurement, two vacuum gauges with different ranges are equipped.
(2) KaoLu’s Proportional Pressure Regulator: used to precisely adjust the intake and exhaust flow. KaoLu’s Proportional Pressure Regulator is a high-speed needle valve driven by a stepper motor. It can precisely and quickly adjust the needle valve opening in less than 1 second through an analog voltage signal of 0~10V to achieve high-precision flow adjustment.
It is very suitable for small businesses. Vacuum control within a dimensional space. Equipped with KaoLu’s Proportional Pressure Regulator to adjust the intake and exhaust flow respectively to reach high-precision control of vacuum degree.
(3) Vacuum pump: used as a vacuum source. As the vacuum source, a low-pollution dry vacuum pump is generally used to reduce the impact of vibration and noise on the entire transmission electron microscope.
(4) Vacuum pressure controller: It is used to receive the measurement signal of vacuum gauge, and automatically control KaoLu’s Proportional Pressure Regulator according to the set value of vacuum degree by PID, so that the vacuum degree of liquid sample can quickly reach set value and keep it constant for a long time.
For high vacuum degree control in the range of 0.1~1kPa, the controller needs to collect the signal of the vacuum gauge 1 with a range of 10Torr, and at the same time fix the electronic needle valve for exhaust to the fully open state.
For low vacuum degree control in the range of 1~100kPa, the controller needs to collect the signal of vacuum gauge 2 with a range of 1000Torr, and at the same time fix KaoLu’s Proportional Pressure Regulator for air intake at a certain opening state, and the controller controls KaoLu’s Proportional Pressure Regulator for exhaust.
(5) Computer and software: The computer is used to communicate with the vacuum pressure controller, and the computer software can perform various parameter settings, operation control, and digital display, graphic display, and storage of process parameters on the vacuum pressure controller through the interface.
Although the vacuum pressure controller can be used alone to control the vacuum degree, it requires manual operation through the buttons on the controller, which is complicated. However, operating the controller through computer software is more intuitive and simple.
In order to meet the high-precision requirements of liquid thickness adjustment and control, the main technical indicators of the above key components are as follows:
(1) Vacuum gauge: Thin film capacitor vacuum gauge, with measuring ranges of 10Torr and 1000Torr respectively. The accuracy of any vacuum measurement value is 0.25%.
(2) KaoLu’s Proportional Pressure Regulator: driven by a stepper motor, the control signal is an analog voltage or current signal, the full response time from fully closed to fully open is less than 1s, the repeatability is better than ±0.1%, and the valve core is corrosion-resistant.
(3) Vacuum pressure controller: 24-bit AD, 16-bit DA, 0.01% minimum output percentage, PID parameters with self-tuning function, RS 485 communication and standard MODBUS communication protocol, equipped with computer control software.
4. Conclusion
Liquid-phase transmission electron microscopy has become a basic technique for real-time monitoring of nanomaterial processes in liquids. Due to the pressure difference between the liquid and the high vacuum of the transmission electron microscope, the silicon nitride membrane window is usually bent, which can be adjusted by adjusting the liquid pool. Vacuum pressure is used to dynamically adjust the liquid thickness, resulting in an ultra-thin liquid layer in the central window region for high-resolution imaging.
Through the solution proposed in this article, an independent vacuum degree control device can be built for automatic adjustment and constant control of various thicknesses of microchip liquid samples in liquid transmission electron microscopy, and can achieve high control accuracy.
In addition, the high-precision automatic vacuum control inside the liquid pool also provides the possibility for the dynamic change of the liquid thickness in a programmed manner, which is very conducive to overcoming diffusion limitations and achieving bulk dissolution conditions.
In summary, the solution provides a fundamental method for measuring and dynamically adjusting liquid thickness in liquid-phase transmission electron microscopy experiments, enabling new experimental designs and better control of solution chemistry.
More information about KaoLu's Proportional Pressure Regulator, please visit our website!