MATERIALS
COC vs COP vs PMMA — Choosing the Right Material for Your Microfluidic Device
Selecting the correct polymer substrate is one of the most critical decisions in microfluidic chip design. The material you choose affects optical properties, chemical compatibility, cost, and ultimately, the success of your assay.
Why Material Choice Matters
Microfluidic devices demand materials that can withstand repeated sterilization, maintain optical transparency for imaging, resist chemical degradation, and be manufactured with precision. The three most common choices—COC, COP, and PMMA—each offer distinct advantages and trade-offs.
For diagnostic assays, sample compatibility is non-negotiable. For analytical instruments, optical clarity and low background fluorescence can make or break your detection sensitivity. For prototyping, cost and ease of machining take priority. Understanding each material's strengths will help you make an informed choice.
COC (Cyclic Olefin Copolymer)
What It Is
COC is a thermoplastic polymer made from ethylene and cyclic monomers. Common brands include TOPAS (by Polyplastics) and ZEONEX (by Zeon). It's widely used in medical devices, diagnostics, and life science applications.
Key Strengths
- Excellent optical clarity (>92% transmittance in UV-Vis)
- Very low autofluorescence—ideal for fluorescence-based assays
- Good chemical resistance to many organic solvents and aqueous solutions
- Moderate cost at volume production
- Excellent for thermal bonding
Considerations
- Moderate water absorption (~0.1%) can affect dimensional stability over time
- Slightly higher cost than PMMA
- Requires more precise processing than acrylic
COP (Cyclic Olefin Polymer)
What It Is
COP (brand name ZEONOR by Zeon) is a close cousin to COC, with slightly different polymer backbone chemistry. The primary difference is superior moisture resistance and water absorption properties.
Key Strengths
- Excellent optical clarity (>92% transmittance)
- Very low autofluorescence—even better than COC in some applications
- Exceptional chemical resistance across a broader range of solvents
- Extremely low water absorption (<0.01%)—best in this category
- Maintains dimensional stability in humid or wet environments
Considerations
- Higher cost than both COC and PMMA
- Fewer commercial sources and suppliers
- More limited bonding method compatibility (thermal and adhesive preferred)
PMMA (Polymethyl Methacrylate / Acrylic)
What It Is
PMMA, commonly known as acrylic, is a transparent thermoplastic that's been used for decades in optical and medical applications. It's affordable, readily available, and easy to machine, making it the go-to material for proof-of-concept devices and high-volume cost-sensitive applications.
Key Strengths
- Lowest cost of the three options—excellent for prototyping and high-volume production
- Excellent optical clarity (>92% transmittance)
- Easy to machine, mill, and cut—ideal for rapid prototyping
- Multiple bonding methods: thermal, adhesive, solvent, and ultrasonic
- Wide availability from numerous suppliers
Considerations
- Lower chemical resistance—organic solvents can cause crazing and stress cracking
- Moderate autofluorescence—not ideal for sensitive fluorescence assays
- Higher water absorption (~0.3%) compared to COC and COP
- Less suitable for long-term storage in wet environments
Material Comparison Summary
| Property | COC | COP | PMMA |
|---|---|---|---|
| Optical Clarity | Excellent (>92% transmittance) | Excellent (>92% transmittance) | Excellent (>92% transmittance) |
| Autofluorescence | Very Low | Very Low | Low to Moderate |
| Chemical Resistance | Good | Excellent | Fair (susceptible to organic solvents) |
| Water Absorption | Moderate (~0.1%) | Very Low (<0.01%) | Low (~0.3%) |
| Bonding Methods | Thermal, adhesive, solvent | Thermal, adhesive | Thermal, adhesive, solvent, ultrasonic |
| Cost (High Volume) | Moderate | High | Low |
| Machinability | Good | Good | Excellent (easy to mill & cut) |
When to Choose Each Material
Choose COC When:
- Building fluorescence-based diagnostics or assays
- You need excellent optical clarity and low background noise
- Chemical compatibility with alcohols, weak acids, and mild solvents is required
- You're balancing cost and performance for moderate-volume production
Choose COP When:
- Your device will be stored or operated in aqueous or humid environments
- Superior chemical resistance to a broad range of solvents is essential
- Dimensional stability over extended periods is critical
- Cost is secondary to performance and reliability
Choose PMMA When:
- Prototyping rapidly with minimal tooling cost
- Manufacturing at high volume where material cost is a significant factor
- Your assay doesn't involve organic solvents or sensitive fluorescence detection
- You need maximum machinability and rapid iterative design
Resources and Next Steps
Choosing the right material is just the first step. Consider these resources to refine your decision:
- View our detailed material comparison table with thermal properties, refractive indices, and more.
- Use our free microfluidic calculators to model flow dynamics and pressure drop for your device geometry.
- Request a quote and discuss your specific application with our material experts.
Material selection ultimately depends on your application's unique demands. If you're uncertain, start with COC for diagnostic work or PMMA for cost-sensitive prototypes, then validate with actual samples before committing to production.