Development and application of microfluidic technology

Microfluidic technology is a new technology platform for controlling extremely small amounts of liquid (10-9~10-18L). Microfluidic technology is widely used in the study of biological problems. Its main characteristics and advantages are that cell culture, experimental processing, imaging, detection and other steps are highly integrated on the chip.

Microfluidic technology has been around for nearly 30 years, but it has developed rapidly and is known as a disruptive technology for the next generation of medical diagnosis. This article will briefly introduce microfluidic technology from three aspects: the important time nodes of the development of microfluidic technology, the main factors to be considered in the development of microflow control chips, and popular application fields.

Important moments in the development of microfluidic technology:

1.1990s.

Manz, Harison and others conducted early chip electrophoresis research and proposed the concept of micro-total analysis system (渭-TAS).

2.1994

Based on Manz's research, Ramsy improved the chip capillary electrophoresis sampling method and improved its performance. In the same year, the first micro TAS conference was held in the Netherlands.

3.1995

The first Caliper company engaged in microfluidic control technology was established, and related companies also closely researched and developed microfluidic control technology.

4.1998

Whiteside proposed a rapid template replication method for making chips using PDMS.

5.1999

Agilent and Caliper jointly launched the first commercial microfluidic chip instrument, which was first used in the fields of biological analysis and clinical analysis.

6.2000

Soft lithography realizes microvalves and micropumps on the chip.

7.2001

Created the journal LabonaChip, which specializes in collecting research articles on microfluidic technology.

8.2002

Large-scale integration of microfluidic control chips.

9.2003

Forbes magazine listed it as one of the inventions that will have the greatest impact on mankind in the next 15 years.

10.2004

Bussiness2.0 magazine called it 7 technologies that will change the future.

Factors to be considered in developing microfluidic chips.

In order to control extremely small amounts of liquid of 10-9~10-18L, how high is the precision of the loading chip! What steps does a chip go through from processing to final formation? What technical issues should be considered in each step? Let's take a look with the editor!

1. Microfluidic chip processing.

This step needs to consider the structure, cost, pipeline size, whether it can be mass-produced, etc. Current technologies include:

Photolithography, hot pressing, molding, injection molding, LIGA (lithography, electroforming, molding), laser ablation, soft lithography.

2. Microfluidic chip packaging.

This step needs to consider the following issues: high temperature performance degradation, room temperature aging, point sealing or surface sealing, whether the pipeline is blocked, and whether it can be mass-produced. The current technologies mainly include:

Plasma/ionization ultrasonic welding, Laser welding, hot pressing bonding, etc.

Third, microfluidic control fluid drive.

This step mainly needs to consider pumps and valves, including whether to choose active or passive type, and whether it is stable and reliable. On the other hand, fluid width, depth, cavity size, quantitative analysis or qualitative analysis need to be considered. The current driving methods mainly include:

light control, electric drive, magnetic field, extruded bubbles, membrane vibration, pump push, centrifugal force, shear force.

Fourth, aerosol pollution design.

This step requires consideration of which material or method to choose to minimize aerosol contamination. The existing methods are as follows:

Sealed reaction system post-expansion, fully sealed system, silicone oil seal, after sample addition, sealed sample hole, buckle structure, manual seal.

Five, instrument signal detection.

Collect microfluidic droplet signals, the main technologies include:

Visual reading, electrical signal reading and expansion curve.

Six, supporting software system.

A good microfluidic control system is not enough with just a chip, but also requires a simple and practical software system, which can greatly enhance the user experience.

Popular application areas:

1.IVD (in vitro diagnosis)

Microflow control chip IVD products have subversive advantages in some aspects and will surely develop into the mainstream in vitro detection technology.

1.1 Organ Chip.

Organ Chip refers to the science and technology of simulating organ functions on a microfluidic control chip platform. It is one of the top ten new technologies selected by the World Davos Forum in 2016. Its main goal is to simulate the biological environment on the chip, culture cells, tissues and organs, study and control the biological behavior of cells in vitro culture, so as to achieve organ transplantation and drug evaluation in a simulated biological environment. Organ Chip is a complex system. Currently, there are clinical applications such as kidney chip, liver chip, islet chip, intestinal chip, vascular glycogen chip, and new tumor products.

1.2 Liquid biopsy.

Taking the detection of circulating tumor cells CTC as an example, it is of great significance in tumor staging detection, dynamic detection, efficacy evaluation, drug development and prognosis detection. It is a new liquid biopsy technology that replaces tumor tissue biopsy. However, CTC immune collection and technical methods relying on single epithelial antibodies cannot fully capture different types of CTCs, are difficult to release CTCs without loss, and cannot provide in-depth molecular pathology information. Through microfluidic control technology, multi-affinity and high-specificity nucleic acid sequences can be obtained, and efficient capture and lossless release of CTCs can be achieved by constructing a microfluidic control microcolumn array chip. This method has important application prospects in the accurate diagnosis, medication guidance and efficacy evaluation of cancer.

2. Environmental and biochemical analysis.

Integrate the mobile integrated valve into the chip to construct a rotating analysis platform, and control the connection and disconnection between channels by rotating the valve to achieve fluid control. Combined with enzyme-linked colorimetric immunoassay and chip, a colorimetric immunosensor based on a microfluidic control chip is constructed to quantitatively analyze the concentration of pollutants according to the intensity of the color signal. This method can analyze a variety of environmental pollutants, with simple operation, high integration and great development potential.

3. Single cell analysis.

Cells are the basis of life, and exploring life health and disease often requires cell research. Due to the differences between cells, the research results of group cells can only get the average value of a group of cells, which often obscures individual difference information. Microfluidic chips provide new ideas for the study of cell biological functions.

4. Nucleic acid analysis.

Microfluidic chip technology is used for PCR expansion and related detection, which can simplify the operation steps and significantly improve the detection efficiency. In this regard, microdroplet digital PCR (ddH2O) based on is a successful example. Digital PCR is a new method for nucleic acid detection and quantification. With the help of microdroplets or micropits, accurate absolute quantification can be achieved by PCR expansion of a single template molecule without relying on standard curves and reference samples. Digital PCR makes the reaction more sensitive, the results more reliable, and the display more intuitive, which is particularly suitable for the detection and quantification of trace or trace DNA.

5. Drug screening.

Drug screening is a step in the modern drug development process to test and obtain specific physiologically active compounds. Microfluidic chip technology has become a very potential and efficient screening tool for drugs and lead compounds due to its low sample consumption, fast speed, high column efficiency, and the solution system used is close to the composition of biological fluids.

The platform can integrate 256 or cell culture chamber microarrays, change the conventional cell culture method, and achieve high-throughput cell drug screening; the chip micro-nano upgrade volume greatly reduces reagent consumption and reduces the cost of drug screening; the two-dimensional structure or three-dimensional microstructure area designed by the microfluidic chip can produce a lower shear force, forming a concentration gradient in the chamber, and then conducting toxicity analysis of the drug; the integration of the microfluidic chip is very obvious, and multiple steps such as drug synthesis separation and enrichment, experimental cell culture, and drug effect detection are combined to achieve automatic analysis of drug screening.

In recent years, microfluidic technology has developed rapidly, with more and more chip-integrated unit components and larger and larger integration scales. At the same time, the microflow control chip can process a large number of samples in parallel, with the characteristics of high throughput, fast analysis speed, low material consumption, and low pollution, providing a powerful platform for the foundation and application of materials, chemistry, life sciences, biomedicine and other fields.

Although there are so many exciting and eye-catching developments, we still face challenges in the field of microfluidics, mainly in the transition between theoretical research concepts and practical technologies for solving real-world problems. Therefore, in the future, we still need to focus on basic research and promote the development of this field, but at the same time, we must also pay attention to the application of microfluidic technology, especially in the field of high throughput. It is believed that microfluidic control products will soon enter the market and play an important role in the development of human life and health and the protection of the ecological environment.