What Is a Micropump?

Micropumps are small, precision pumps.

They are used in analytical instruments and in the medical, biotechnology, and nanotechnology fields for controlling and manipulating microscopic liquids. Micropumps can be classified into mechanical types, which require a mechanical power mechanism, and non-mechanical types, which are driven by physical external forces.

Applications of Micropumps

Micropumps are used in precision instruments, medical devices, biotechnology, and nanotechnology. They also play an important role in devices that are becoming increasingly miniaturized.

For example, in medical devices, micropumps are used for insulin infusion in artificial kidneys and built into artificial hearts. They are also used in rare chemical experimentation and have many other uses across various fields.

Mechanical micropumps are most commonly sold, but non-mechanical micropumps may be more appropriate for some applications.

Principle of Micropumps

Micropumps consist mainly of a pump head and a driver. The pump head transports the fluid and is usually made of silicon. The driver moves the pump head and is generally controlled using electrical signals. They also comprise other electronic components, such as control circuits and power supplies.

There are also pressure-driven, non-mechanical, and light-driven pumps, micropumps operated by nanomotors, and even micropumps that use capillary action.

1. Pressure-Driven Pumps

Pressure-driven pumps use the pressure differences inside and outside of a pump to move liquid. By increasing the pressure inside the pump to push the liquid out, the external low pressure creates the force to suck the liquid out.

Pressure-driven micropumps are highly accurate and reliable, and there are many types available for a variety of applications. For example, there are some designed to handle high pressures and others suitable for moving minute amounts of liquid. The relatively simple structure makes them low-cost to manufacture and suitable for a wide range of applications.

2. Light-Driven Micropump

Light-driven micropumps use light energy to move liquids. Shining light onto the surface of the liquid generates the pressure needed to move the liquid. They are mainly used in the biotechnology field and can pump liquid through minute channels.

However, since light-driven pumps require a light source, they are susceptible to external influences, and their performance may vary depending on the light intensity and direction of the light source.

3. Nanomotor Micropump

Nanomotor micropumps use nanomotors, which can convert intracellular energy into mechanical movement, to transport liquids. Driven by an energy source such as a magnetic or electric field, they can operate even in very small spaces. 

4. Capillary Micropump

Capillary action micropumps use capillary action to transfer liquid in a minute flow path.

A thin tube is placed inside the microchannel and filled with liquid. Then, the surface tension created by bending the narrow tube propels the liquid upward. This makes it possible to transfer liquid through very small channels.

Features of Micropumps

The most important feature of micropumps is their small size. Since they can move fluids through such small channels, they can be used in many microscale applications, such as microfluidics research and the development of tiny biochips.

Micropumps can also be manufactured at a low cost due to the small number of components required for a pump and the relative ease of manufacture. This facilitates mass production and is widely used in fields such as medicine and biology.

What Is a Network Analyzer?

A network analyzer is a test instrument that evaluates the network characteristics of a device under test (DUT). This is done by measuring certain key S-parameters on multi-port networks.

Specifically, it can measure the attenuation and impedance of the input signal to the DUT. In particular, it can evaluate the high-frequency characteristics of electronic components, etc., and has a wide range of applications, including the ability to perform measurements on transmission devices. Such measurements can be conducted on microwave systems, common WIFI networks, corporate networks, basic computer-to-computer connections, and even on large-scale cell phone networks. 

The output of a network analyzer is represented by the S-parameter (scattering parameter), which defines the physical quantities known as forward reflection (S11), forward transmission (S21), reverse transmission (S12), and reverse reflection (S22). This is typically the case with a 2-port network, but the devices or connections being tested may have more than 2 ports. Whatever the network situation, the correct Network Analyzer must be chosen to match the number of ports present. This is a basic premise but an important one if the reflection and loss parameters are to be accurately calculated.

Uses of Network Analyzers

Network analyzers are broadly classified into scalar network analyzers and vector network analyzers (VNA), of which vector network analyzers (VNA), which provide not only amplitude information but also phase information, have a wider range of uses.

The advantages of network analyzers for high-frequency applications are used in the development of matching circuits for high-frequency amplifiers. Here, the design is based on accurate S-parameters for each amplifier, antenna, and/or filter.

In many cases, a network analyzer is also used to evaluate impedance matching. This is because impedance mismatch in the transmission lines of each device or cable in a high-frequency handling circuit network can cause power loss or signal distortion.

Principles of Network Analyzers

A network analyzer is equipped with a signal source, a signal separator, a directional coupler, and at least three receivers.

• Signal Source                                           
  The signal source provides the signal to the system and is supplied by a synthesizer module.

• Signal Separator                                        
  The signal separator uses a resistor splitter to split the input signal into circuit signals and receivers (reference signal R).
• Directional Coupler                                    
  The directional coupler separates the input wave from the reflected wave, which is measured at the receiver (reference signal A).

The output of the DUT is measured at a third receiver (transmission signal B). Evaluation is performed by comparing the signals (e.g., S11 is defined by A/R and S21 by B/R).

Accurate measurement of the network analyzer is ensured by precise calibration. For calibration, a standard device with known characteristics is used. A commonly used calibration method is the SOLT method, in which a short-circuit, open-circuit, and load-capable standard are coupled to a reference plane in a direct connection (thru).

Since this is a very precise measurement, care must be taken to avoid measurement errors in various aspects such as connector tightening torque, ambient temperature, input signal, cable stability, etc.

Other Information on Network Analyzers

1.  Basic Knowledge of Network Analyzers  

There are two types of network analyzers: vector network analyzers (VNA) and scalar network analyzers. Vector network analyzers are widely used these days.

Network analyzers have a method of measuring amplitude changes in transmission and reflection measurements called S-parameters. S-parameters are also called S-matrices, and there is a numbering system for their definition. The numbering scheme is “Sij i=output port, j=input port,” where S11 represents the coefficient of a signal incident at port 1 that has been transmitted to port 1, S12 represents the coefficient of a signal incident at port 2 that is transmitted to port 1.

The S parameter can be measured by using a VNA measuring instrument. However, the VNA must be calibrated using several calibration methods before measurement.

The basic method of VNA calibration is to use three standard instruments. Widely known calibration methods include the SOLT calibration method, the UnKnown Thru calibration method, and the TRL calibration method described above.

2. About Impedance Measurement

Impedance is an important parameter used to characterize electronic circuits, electronic components, and electronic materials. It is the amount of opposition to an alternating current (AC) that interrupts a circuit or other device at a certain frequency. There are various types of impedance measurement methods, each with its advantages and disadvantages.

The measurement method must be selected in consideration of the frequency range required for the measurement and the resistance and reactance conditions of the impedance measurement range. Measurement methods include the bridge method, resonance method, I-V method, network analysis method, time domain network analysis method, and automatic balanced bridge method.

The bridge method is explained as an example. The advantages of the bridge method are its high accuracy (around 0.1%), its ability to cover a wide frequency range with multiple measuring instruments, and its low cost. On the other hand, one demerit of the bridge method is that it requires a balance operation, and a single unit can cover only a narrow range of frequencies. The bridge method’s measurement frequency range is approximately 300-MHz DC.

3. Trends in Frequency Extension

The maximum frequency extension of network analyzers now extends into the sub-THz band (220 GHz). This is because it is predicted that the next generation communication standard, 6G, will most likely use the 140 GHz band, known as the D-band.

However, because of its high frequency, the sub-THz band is susceptible to electrical length errors, parasitic elements, and other measurement discontinuities, making total calibration accuracy, including that of the RF probe tips and cables, extremely important.

In reality, the frequency range that can be calibrated at one time is often limited, and manufacturers are competing to develop easy-to-use measuring instruments, including the handling of data between calibrations and the addition of frequency extenders dedicated to the millimeter wave band.

4. Addition of Modulated Power Evaluation Function, Etc.

Generally speaking, Network analyzers are used to evaluate the impedance of DUTs and S-parameters, which are small signals. Therefore, models that enable network analyzers to perform modulation analysis, which is mainly handled by conventional spectrum analyzers, are gradually being released. With wireless technologies on the increase, the ability to examine complex RF (Radio Frequency) bands is an essential feature, one worth integrating into a Network Analyzer.

In the future, network analyzers will be used not only for impedance and S-parameter evaluation but also for evaluating switches, filters, high-frequency (RF) amplifiers, low-noise amplifiers (LNA), and other RF front ends, including large-signal analysis and modulation analysis.

What Is a High Voltage Power Supply Unit?

A high-voltage power supply unit is a power supply unit that handles particularly high voltages.

High voltage generally refers to voltages ranging from several thousand volts (V = volts: a unit of voltage) to several tens of thousands of V or higher. The voltage transmitted by power companies is 6.6 kV or higher, but high voltage is generally defined as 600 V AC (750 V DC) or higher.

The electrical appliances we use in our daily lives have low voltages of 100 VAC or 200 VAC. This is due to the fact that the standard power supply voltage transmitted from the power company’s generation facilities to each household is either 100 VAC or 200 VAC.

Although typical power supply units are 100 VAC or 200 VAC, some equipment may want to generate higher voltages depending on the conditions of use. Specifically, these are devices that require higher voltages than the power supply voltage or devices to be tested for tolerance to high voltages. In order to clear this requirement, a transducer that generates higher voltage than the power supply voltage used by general users is needed. High-voltage power supply units are used in such cases.

Uses of Applications of High Voltage Power Supply Units

High-voltage power supply units are mainly used for operating products that require high voltages and to withstand voltage testing.

Examples of equipment that require high voltage include equipment used for painting automobile bodies and construction materials, equipment used for surface treatment of metals and plastics, X-ray radiation equipment used for radiation therapy and x-rays, and electron microscopes.

Pressure resistance testing is performed on industrial electrical equipment such as electric wires. Products are often tested to withstand voltages of 1500 V for 1 minute or 1800 V for 1 second before shipment, and that insulation withstand voltages be tested. Therefore, the introduction of high-voltage power supply units is mandatory. They are also used for practical training to acquire qualifications as high voltage and special high voltage electricity handlers.

Principle of High Voltage Power Supply Units

High-voltage power supply units are converters that input general AC power transmitted to the end of the line and output it as high-voltage. A converter is a device (unit) that converts the AC power supply voltage transmitted from the power company into DC voltage using a circuit with diodes called a rectifier and smoothes the voltage with an electrolytic capacitor.

However, simply using a converter unit will only output a DC voltage that is smoothed at a low voltage because it is 100V or 200V, and will not provide the high voltage of 10 times or 100 times or more the voltage originally desired. It is possible to boost the voltage simply by the turn ratio of the step-up transformer, but the turn ratio has a practical limit.

To obtain a high voltage, a Cockcroft-Walton circuit combining a diode and a capacitor is used. This method uses the storage capacity of the capacitor and the rectifying action of the diode. After the capacitor stores electricity in response to an AC input in one direction, the voltage is boosted when a current flows in the opposite direction.

This circuit method is commonly used to raise the voltage by layering the rectifier-based circuit described earlier and is also referred to as a doubling voltage circuit or a high-voltage generator circuit among technical personnel. Since the voltage increase is an even multiplication, it is not possible to boost the voltage by an odd number of times. High voltages of 1 kV or higher can be obtained by combining an appropriate high voltage diode and ceramic capacitor.

Other Information on High Voltage Power Supply Units

1. High Voltage Power Supply Module

High-voltage power supply modules are high-voltage compatible power supply units capable of supplying high voltages that generally generate 1 kV or more.

Among these, power supply unit manufacturers with an established reputation for their technological expertise in downsizing through higher efficiency while ensuring low noise and reliability have achieved low prices by improving the quantity and ease of use of their products, and have modularized their high-voltage output power supply modules as general-purpose products.

Major manufacturers and products of high-voltage power supply modules include the OHV series by Bellnix, the TCR series by American High Voltage; the HGP series by Matsusada Precision, HitekPower by General Products; the TMK series by Takasago Machinery Works, the C14051 series by Hamamatsu Photonics, etc. The more the output current increases in addition to the original high voltage, the larger the size of the module becomes. Therefore, it is necessary to select a module with attention to its margin, temperature rise, and dielectric strength depending on the actual use of the load. 

2. High-Voltage Power Supply Board

The substrate of a high-voltage power supply is a high-voltage circuit, so there are some precautions that must be taken for the substrate used in the high-voltage circuit. This is because the higher the voltage, the more the standard requires that the insulation distance of the board be sufficiently secured. The higher the voltage is, the greater the possibility of serious electric shock during work. To ensure safety, safety measures against withstand voltage and electric shock must be taken, including the creepage distance and insulation distance of the circuit board and the installation of safety grounding.

In practice, the IEC standard absolutely requires a board pattern design that ensures insulation distances between conductive copper foil patterns on the board based on each country’s standards. Failure to comply with this requirement may result in fines or other penalties as a violation of the law, and not only penalties, but also a loss of social credibility. Therefore, both the manufacturer and the user must be very careful to ensure that the insulation distance of the board pattern meets the standard.