Cyclic olefin polymers (COP) and copolymers (COC) have emerged as leading materials for advanced microfluidic and bioanalytical devices. Their popularity is driven by a unique combination of properties, including excellent optical transparency, low autofluorescence, high chemical resistance, and low water absorption. These materials are also compatible with high-throughput manufacturing techniques such as injection molding and hot embossing, enabling scalable production of disposable lab-on-a-chip systems.
Compared to traditional materials such as glass or PDMS, COP offers superior barrier properties to gases and moisture, improved mechanical stability, and reduced absorption of small molecules, making it particularly well suited for biological and diagnostic applications. However, a key limitation of COP is its inherently hydrophobic surface (typical water contact angles >80°), which can hinder fluid flow, bonding, coating adhesion, and biological interactions.
Plasma surface treatment provides an effective, controllable method to overcome these limitations by introducing polar functional groups and increasing surface energy.
Plasma Treatment of Cyclic olefin polymers (COP)
Plasma treatment modifies COP surfaces through exposure to reactive species (ions, radicals, and excited molecules), which introduce oxygen-containing functional groups such as hydroxyl and carboxyl moieties. This results in:
- Increased surface energy and wettability
- Improved adhesion of coatings and biomolecules
- Enhanced bonding between polymer layers
- Tunable surface chemistry for specific applications
These modifications are critical in enabling COP to function effectively in microfluidic and biointerface environments.
Microfluidic Applications
In microfluidic device assembly, plasma treatment enables strong, uniform bonding at temperatures below the bulk glass transition temperature (Tg), preserving channel geometry and preventing deformation. Additionally, plasma lowers the surface Tg locally, facilitating effective sealing of microchannels without compromising structural integrity.
Wettability Control and Fluid Handling
The hydrophobic nature of COP can impede fluid filling and control. Plasma treatment increases hydrophilicity, allowing:
- Improved capillary flow in microchannels
- Reduced bubble formation
- Enhanced reproducibility in fluid handling
Cell-Based Microfluidics
Surface wettability strongly influences protein adsorption and cell adhesion. Plasma-treated COP surfaces promote adsorption of extracellular matrix proteins (e.g., fibronectin, collagen), which enhances cell attachment and proliferation.
Furthermore, plasma-based patterning techniques enable spatial control of wettability, allowing selective cell growth and micropatterning, critical for tissue engineering and lab-on-chip assays.
Device Fabrication and Integration
Plasma treatment is widely used in:
- Bonding multilayer microfluidic chips
- Activating surfaces prior to coating or functionalization
- Preparing interfaces for hybrid material systems (e.g., COP-PDMS devices)
Cyclic olefin polymers (COP) Microfluidic Articles
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Rodrigues, R. G., Condelipes, P. G. M., Rosa, R. R., Chu, V., & Conde, J. P. (2023). Scalable processing of cyclic olefin copolymer (COC) microfluidic biochips. Micromachines, 14(10), 1837. https://doi.org/10.3390/mi14101837
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Chantiwas, R., Hupert, M. L., Pullagurla, S. R., Balamurugan, S., Tamarit-Lopez, J., Park, S., Datta, P., Goettert, J., Choe, Y.-K., & Soper, S. A. (2010). Simple replication methods for producing nanoslits in thermoplastics and the transport dynamics of double-stranded DNA through these slits. Lab on a Chip, 10, 3255–3264. https://doi.org/10.1039/c0lc00096e
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Meng, X., Yu, Y., Gong, P., & Jin, G. (2021). An integrated droplet digital PCR gene chip for absolute quantification of nucleic acid. Microfluidics and Nanofluidics, 25, 62. https://doi.org/10.1007/s10404-021-02465-4
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Cyclic olefin polymers (COP) & Graphene Oxide
Graphene oxide coatings enhance surface functionality by introducing stable hydrophilic regions on otherwise hydrophobic COP surfaces. Compared to plasma treatment alone, GO coatings can provide longer-lasting wettability and increased surface roughness, improving biological interactions and device performance.
Plasma-assisted processes enable precise patterning of GO and rGO films through techniques such as plasma-enhanced lift-off. These patterned films can be integrated into microfluidic systems for:
- Transparent and flexible electrodes
- Biosensing interfaces
- Electrokinetic manipulation of cells (e.g., dielectrophoresis)
Cyclic olefin polymers (COP) & Graphene Oxide Articles
Alazzam, A. (2020). Solution-based, flexible, and transparent patterned reduced graphene oxide electrodes for lab-on-chip applications. Nanotechnology, 31(7), 075302. https://doi.org/10.1088/1361-6528/ab50ee
Al-Azzam, N., & Alazzam, A. (2022). Micropatterning of cells via adjusting surface wettability using plasma treatment and graphene oxide deposition. PLOS ONE, 17(6), e0269914. https://doi.org/10.1371/journal.pone.0269914
Conclusion
Cyclic olefin polymers offer an exceptional platform for next-generation microfluidic and bioanalytical devices, combining manufacturability with high-performance material properties. However, their native hydrophobicity limits direct use in many applications.
Plasma treatment provides a versatile and scalable solution to this challenge by enabling precise control of surface chemistry, wettability, and adhesion. From improving microfluidic bonding and fluid handling to enabling advanced graphene-based functionalities, plasma processes are essential for unlocking the full potential of COP materials.
As microfluidic technologies continue to evolve toward more integrated, functional, and scalable systems, plasma surface modification remains a critical enabling technology—positioning Harrick Plasma systems at the forefront of innovation in polymer surface engineering.