Custom processing of plastic microfluidic chips

Microfluidic plastic chips are tiny laboratory devices made from polymer materials, featuring microchannels and microchambers for controlling and analyzing microfluidics. Compared to traditional glass chips, plastic chips offer advantages such as lower cost, more flexible fabrication, and easier processing.

These chips are widely used in biomedicine, chemical analysis, and environmental monitoring. Their tiny size and high integration enable efficient microreactions, cell culture, drug screening, and other experiments, providing a convenient tool for laboratory research.

Microfluidic plastic chips play a crucial role in advancing microfluidic technology and promoting the automation and high-throughput of laboratory experiments.

1 Microfluidic Plastic Chip Materials

1.1 Polymethyl methacrylate (PMMA)

PMMA is an inexpensive and easily manufactured polymer. It is the least hydrophobic polymer among common plastics and is easily modified.

Due to its low price, rigid mechanical properties, excellent optical transparency, and compatibility with electrophoresis, it is particularly useful for disposable microfluidic plastic chips. It is also an ideal material for preparing reusable microfluidic plastic chips.

Advantages of PMMA chips: Low cost, the least hydrophobic polymer among common plastic materials, rigid mechanical properties, excellent optical transparency, compatibility with electrophoresis, easy to manufacture and modify, and reusable.

Disadvantages of PMMA chips: Requires expensive equipment to create complex chips from this polymer (injection molding, thermoforming).

Common applications of PMMA chips: Ecological microchips (reusable), mixed analysis chips, DNA sequencers, electrophoresis chips.

PMMA chip molding methods: CO2-laser micromachining, injection molding, thermoforming, compression molding, and extrusion molding.

Glass transition temperature: 85-165℃ (different grades).

1.2 Cyclic Olefin Copolymers (COC)

COC chips exhibit good resistance to hydrolysis, acidic reagents, alkaline reagents, and most polar organic solvents, such as acetone, methanol, and isopropanol. COC chip materials have high transparency to light wavelengths above 250nm and exhibit low autofluorescence.

Due to the hydrophobic surface of COC chips, chips made from them are prone to spontaneous, non-specific protein adsorption and cell adhesion when exposed to biological tissues or liquids, making them unsuitable as the optimal choice for drug-related research.

Advantages of COC chips: Good resistance to hydrolysis, acids, alkalis, and most polar organic solvents; high transparency to light wavelengths above 250 nm; low autofluorescence; low birefringence; high Abbe number; high heat resistance; low water absorption; high dimensional stability.

Disadvantages of COC chips: Injection molding and hydrophobic surface treatment to reduce analyte adsorption and cell adhesion require expensive equipment.

COC chip molding methods: Single-screw and twin-screw extrusion, injection molding, injection blow molding and stretch blow molding (ISBM), compression molding, extrusion coating, biaxial orientation, thermoforming, etc.

Glass transition temperature: 70-177℃ (depending on polymer content).

1.3 Polycarbonate (PC)

Polycarbonate (PC) is the preferred durable material for a range of microfluidic applications in biomedical research and bioanalysis, including DNA thermal cycling applications such as polymerase chain reaction (PCR), due to its visible light transparency and extremely high glass transition temperature (145°C).

Advantages of PC chips: Durable material, transparency in the visible light region, very high glass transition temperature (~145°C), low cost, high impact resistance, low hygroscopicity, and good processability;

Disadvantages of PC chips: Poor resistance to certain organic solvents, UV absorption, limited bonding quality and strength (thermal bonding only), and alteration of channel geometry due to bonding temperature;

Common applications: DNA thermal cycling, fabrication of multilayer devices, enzymatic amplification, nucleic acid separation, amplicon labeling, pathogen detection, and micro-flow injection amperometric glucose determination;

Glass transition temperature: 145-155°C.

1.4 Polystyrene (PS)

Polystyrene (PS) is an optically transparent, inert, biocompatible, rigid, inexpensive, and readily commercializable thermoplastic material, making it one of the most commonly used materials in cell culture.

Its surface is easily treated (using a variety of physical and chemical methods, including irradiation, corona discharge, or gas plasma), making its hydrophobic surface more hydrophilic.

However, the need for expensive equipment to process and manufacture complex chips from this polymer (injection molding, hot pressing) is a major drawback in chip prototyping development, as PS is better suited for large-scale manufacturing processes.

Advantages of PS chips: Optically transparent, biocompatible, inert, easy to process, adaptable to large-scale manufacturing processes, high commercial availability, inexpensive, and quick to bond;

Disadvantages of PS chips: Expensive equipment required for fabricating complex chips using this polymer; difficulties encountered in the thermal bonding step: more channels collapse when the width-to-height ratio is too high;

Common applications: Cell culture research;

Potential applications: Cell culture on microfluidic chips (organ-on-a-chip), using plasma treatment or masking layers, or pre-coating microchannels with extracellular matrix proteins before cell seeding to facilitate cell adhesion and growth while preventing bubble formation;

Molding methods: Injection molding, thermoforming;

Glass transition temperature: 92-107℃;

2. Processing methods: Main processing methods include machining, thermoforming, and injection molding.

Currently, we primarily use machining in the sample prototyping stage; injection molding is the main method in the mass production stage. We have various types of processing equipment to meet the processing needs of different customers at different stages.

3. Bonding Methods The main bonding methods for microfluidic plastic chips include thermoforming, ultrasonic bonding, and laser bonding. Currently, we primarily use thermoforming.