Common Materials and Properties of Microfluidic Chips

Microfluidic chip is based on the development of microelectromechanical systems (MEMS), through the microfabrication technology of microchannels, microvalves, micro-pumps and microelectrodes and other different functions of the micro-components are integrated together to constitute the micro-analytical system.

As the carrier of the microfluidic chip, the chip material determines the processing difficulty, precision, functionality, and cost of the chip, and the selection of the chip material generally takes into account its chemical and biocompatibility, electrical insulation, heat dissipation, modifiability, optical properties, material and processing costs, etc. The chip material can be used in a wide range of applications, including microfluidic chips, microfluidic chips, and microfluidic chips.

The choice of material for microfluidic chip fabrication is a key determinant. Initially, silicon material dominated the microfluidic chip preparation due to its superior properties, but with the diversification of the application scenarios, the limitations of silicon material are gradually revealed, especially its defects of not being able to withstand high voltage and not being compatible with optical detection technology.

To overcome these problems, the industry and research community have begun to explore new material options. Glass is theoretically well suited for the fabrication of microfluidic chips due to its excellent electroosmotic and optical properties, however, its complex fabrication process, expensive cost, and difficulty in photolithography and etching limit its large-scale application.

Compared with this, polymer materials show obvious advantages. Polymer production process is simple, the cost of raw materials is low, at the same time has good insulation, high voltage resistance, thermal stability, biocompatibility, gas permeability and low elastic modulus and other characteristics. These properties make them widely used in capillary electrophoresis microchips, biochemical reaction chips, and a variety of optical detection systems.

At present, organic polymers represented by polydimethylsiloxane (PDMS) have become one of the mainstream materials for microfluidic chip fabrication, and their excellent performance and relatively simple fabrication process have made them widely popular.

Commonly used materials for microfluidic chips and their properties
Performance indicators	galss	PDMS	PMMA	PC	paper base
biocompatibility	comparatively good	susceptible to non-specific adsorption	comparatively good	comparatively good	comparatively good
Optical properties	comparatively good	comparatively good	comparatively good	Poor UV absorption	Low detection background
thermal conductivity	comparatively good	low	low	low	low
electrical insulation	comparatively good	comparatively good	comparatively good	comparatively good	comparatively good
thermal stability	－８０～８６０℃	－５０～２００℃	－８０～９０℃	－６０～１２０℃	Easily evaporated by heat
Cost of materials	Moderate	Moderate	Moderate	Moderate	low
processing difficulty	relatively difficult	Moderate	Moderate	Moderate	easy

silicon

vantage

• Good chemical inertness and thermal stability
• Good finish, mature processing
• Molds for polymer chips, etc.

drawbacks

• Fragile and expensive
• Cannot pass UV light
• Insufficient electrical insulation properties
• Complex surface chemical behavior

Glass quartz materials

vantage

• Very good electroosmotic and optical properties
• Favorable for surface modification by chemical methods
• Can be processed by photolithography and etching techniques

drawbacks

• Difficult to get a channel with a large depth to width ratio
• Higher processing costs
• Sealing is difficult

Organic polymer materials

vantage

• Low cost, variety, low price for mass production
• Available in visible and ultraviolet light
• Surface modification by chemical methods
• Easily processed to obtain a channel with a large width-to-depth ratio

drawbacks

• heat-resistant
• Low thermal conductivity
• Surface modification methods are not yet mature enough

Paper chip material

vantage

• Low cost, no templates required, no constraints on structural design
• The analysis system is easily miniaturized and portable. No external drive pump required, paper folds for easy storage and transportation
• Good biocompatibility
• Low detection background. Paper is usually white, which facilitates colorimetric analysis on paper chips
• Easy to dispose of after use, no contamination

drawbacks

• Sample residue in the paper channel and evaporation of the sample during transport result in reduced sample utilization.
• For some samples with low surface tension, the hydrophobic region is not necessarily sufficiently hydrophobic and the sample may leak.
• Combined with the traditional colorimetric method, the analytical paper chip cannot detect samples with too low a concentration.