Fabrication, characteristics and bonding methods of microfluidic chips

The use of microfluidics, a chip analysis technology, originated from the chip laboratory in the United States. After the development in Europe, it was made into a micro-integrated analysis chip and finally realized the microfluidic analysis technology as the main platform. The microfluidic chip analysis technology process can be completed automatically, integrating basic operation units such as biological, chemical, and medical analysis sample preparation, reaction, separation, and detection.

The main materials of microfluidic chips are silicon wafers, glass, polydimethylsiloxane (PDMS), polymethyl methacrylate, polytetrafluoroethylene, and paper-based materials. Among them, PDMS is the most widely used. This material is not only simple to process, optically transparent, but also has a certain degree of elasticity. It can produce functional components such as microvalves and microperistaltic pumps.

Microfluidic chips use micro-electromechanical processing technology similar to semiconductors to build a microfluidic system on the chip, and transfer the experimental analysis process to the chip structure composed of connection paths and liquid phase chambers. After loading the biological sample and reaction solution, a micromechanical pump is used. The electric pump and electroosmotic flow drive the flow of buffer in the chip to form a microchannel, and one or more continuous reactions are carried out on the chip. Laser-induced fluorescence, electrochemical, chemical and other detection systems, combined with various analysis methods such as mass spectrometry, have been used for fast, accurate and high-throughput sample analysis of microfluidic chips.

Features of microfluidic technology.

Multifunctional integrated system and large-scale composite system are the biggest features of microfluidic chips.

Microfluidic technology advantages

Microfluidic chips can integrate a series of basic operation units such as sample preparation, reaction, separation, and detection involved in the fields of chemistry and biology into micron chips. At the same time, the network formed by microchannels can run through the entire system, with the advantages of portability, low energy consumption, easy production, and easy mastering, which can easily meet the needs of life sciences for low-dose, high-efficiency, high-sensitivity, and rapid separation and analysis.

1. Integrated miniaturization and automation.

Microfluidic technology can concentrate multiple steps of sample detection on a small chip. These operation steps can be integrated through the combination of flow channel size and curvature, microvalve and cavity design, ultimately making the entire detection integrated miniaturized and automated.

2. High throughput

Since microfluidic control can be designed into multiple channels, it can be transferred to multiple reaction units through the microfluidic network and isolated from each other so that each reaction does not interfere with each other. Therefore, multiple items can be tested in parallel as needed. Compared with the traditional item-by-item test, it greatly shortens the test time, improves the test efficiency, and has the characteristics of high throughput.

3. Less reagent consumption

Due to the miniaturization of integrated detection, the reaction unit cavity on the microfluidic chip is very small. Although the concentration of the reagent formula may increase by a certain proportion, the amount of reagent used is much lower than that of traditional reagents, which greatly reduces the consumption of reagents.

4. Small sample volume

Because the test is only completed on a small chip, the sample volume that needs to be tested is very small, usually only microliters (渭L) or even nl levels. In addition, whole blood can also be tested directly. For infants, the elderly, the disabled and difficult venous collection, the test is more convenient; or very precious and rare samples make many indicators detectable.

5. Less pollution

Due to the integrated function of the microfluidic chip, all operations that need to be done manually in the laboratory are integrated into the chip to minimize the pollution of the sample to the environment.

Disadvantages and shortcomings of microfluidics.

The core technology lacks specifications and standards.

There is a serious shortage of relevant talents.

Currently the production cost is high.

Preparation of microfluidic chip

Different material properties determine different micro-machining methods. However, the main processing methods for microfluidic chips are photolithography and surface pattern soft lithography.

1. Microfluidic chip processing

This step needs to consider issues such as structure, cost, pipeline size, and batch production. Current technologies include: photolithography, hot pressing, molding, injection molding, LIGA (integrated lithography, electroforming, and plastic casting), laser ablation, and soft lithography.

2.Microfluidic chip bonding

Issues that need to be considered in this step include: high temperature performance degradation, room temperature aging, point sealing or surface sealing, pipeline blockage and large-scale production. At present, the main technologies include: Plasma/ionization bonding, film bonding, ultrasonic welding, laser bonding welding and thermal compression bonding.

3. Microfluidic control fluid drive

This step mainly considers pumps and valves, including active or passive choices, and whether they are stable and reliable. On the other hand, fluid width, depth, chamber size, quantitative analysis or qualitative analysis need to be considered. At present, the main driving methods are: light control, electric drive, magnetic field, extruded vesicles, membrane vibration, pump push, centrifugal force and shear force.

4. Aerosol contamination design

This step requires consideration of selecting materials or methods that minimize aerosol contamination. Currently, the following methods can be used: extended sealed reaction system, fully sealed system, silicone oil seal, sample addition, sealed sample hole, buckle structure, and manual seal.

5.Instrument signal detection

The main technologies for collecting microfluidic droplet signals are: visual reading, electrical signal reading and expansion curve.

Application of microfluidics in the field of in vitro diagnosis.