Harrick Plasma → Applications → Life Sciences → Microfluidics →
Plasma cleaning and activation are the near-universal first step for working with PMMA in microfluidics. Exposing PMMA to oxygen or air plasma breaks surface polymer chains and grafts oxygen-containing groups such as hydroxyl and carboxyl onto the surface. The practical consequences are immediate: water contact angle drops, surface energy and wettability rise, and the surface becomes chemically reactive. Researchers exploit that reactivity either directly (for wetting and bonding) or as a handle for subsequent chemistries (silanes, EDC–NHS, fluorosilanes, PVA).
In the following application note you will find application-organized guidance, representative plasma recipes drawn from the literature, and practical tips for bonding, biofunctionalization, wettability control and PMMA Microfluidic devices.
Bonding & Fabrication
Plasma activation is the standard first step for PMMA joining and assembly because it converts an otherwise inert, hydrophobic surface into a wettable, chemically reactive one. After oxygen or air plasma the PMMA surface exhibits lower contact angle and new oxygen-containing functional groups, which improves surface contact for thermal fusion, increases adhesion for solvent-assisted or adhesive seals, and provides the chemistry needed for silane- or reagent-mediated coupling. The literature shows plasma paired with many downstream joining strategies from classical thermal fusion and solvent-softening through two-step adhesive methods, to silane coupling and the newer water-assisted microwave bonding technique and highlights that plasma dose, timing and the choice of post-plasma chemistry control final bond strength and coverage.
Bonding & Fabrication Articles
Brown, L., Koerner, T., Horton, J. H., & Oleschuk, R. D. (2006). Fabrication and characterization of poly(methylmethacrylate) microfluidic devices bonded using surface modifications and solvents. Lab on a Chip, 6(1), 66–73. https://doi.org/10.1039/b512179e
Kentsch, J., Breisch, S., & Stezle, M. (2006). Low temperature adhesion bonding for BioMEMS. Journal of Micromechanics and Microengineering, 16(4), 802–807. https://doi.org/10.1088/0960-1317/16/4/017
Chantiwas, R., Hupert, M. L., Pullagurla, S. R., Balamurugan, S., Tamarit-Lopez, J., Park, S., Datta, P., Goettert, J., Cho, 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(23), 3255–3264. https://doi.org/10.1039/c0lc00096e
Chen, P.-C., & Chen, C.-C. (2017). Addition of structural features and two-step adhesive bond method to improve bonding quality of thermoplastic microfiltration chip. Sensors and Actuators A: Physical, 258, 105–114. https://doi.org/10.1016/j.sna.2017.03.006
Qin, D., Xia, Y., & Whitesides, G. M. (2010). Soft lithography for micro-and nanoscale patterning. Nature Protocols, 5(3), 491–502. https://doi.org/10.1038/nprot.2009.234
Vo, T. N. A., & Chen, P. C. (2021). Maximizing interfacial bonding strength between PDMS and PMMA substrates for manufacturing hybrid microfluidic devices withstanding extremely high flow rate. Sensors and Actuators A: Physical, 334. https://www.sciencedirect.com/science/article/pii/S0924424721007937
Vo, T. N. A., & Chen, P. C. (2022). Maximizing Heterogeneous Bonding Strength Between PDMS/PMMA For Manufacturing Elastomer Microvalve System with High-Density Configuration. In Proceedings of IEEE MEMS 2022. https://ieeexplore.ieee.org/document/9699611
Tsao, C. W., Chang, C. Y., Hu, W. W., & Tian, Y. S. (2023). Bonding of thermoplastic microfluidic device by water assistance. International Journal of Adhesion and Adhesives, 125. https://www.sciencedirect.com/science/article/pii/S0143749623001094
Tsao, C. W., Chang, C. Y., Wei-Wen, H., & Tian, Y. S. (2022). Water-assisted bonding of thermoplastic microfluidic device for biological applications [Preprint]. SSRN. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4020640
Chen, P.-C., Tang, G.-R., Zhang, R.-H., Wu, C.-C., & Tang, G.-R. (2017). Microfabricated microfluidic platforms for creating microlens arrays. Optics Express, 25(14), 16101–16115. https://doi.org/10.1364/OE.25.016101
PDMS-PMMA & Other Heterogeneous Bonding
When PMMA must be bonded to elastomers, metals or functional membranes, plasma provides the –OH functionality that is the gateway to silane chemistries and covalent coupling. The common workflow is plasma oxidation of both mating surfaces, immediate or rapid silanization (for example APTES on PDMS, GPTMS on PMMA), and controlled mating to form amine–epoxy or similar covalent bonds. Papers in the following resources section demonstrate that properly optimized plasma + silane workflows produce hybrid interfaces and microvalves that survive very high liquid pressures and tensile stresses; they also stress the importance of sequence and timing (activate → silanize → mate quickly) and of instrument-specific tuning of power/pressure/time for reproducible results.
PDMS-PMMA & Other Heterogeneous Bonding Articles
Vo, T. N. A., & Chen, P. C. (2021). Maximizing interfacial bonding strength between PDMS and PMMA substrates for manufacturing hybrid microfluidic devices withstanding extremely high flow rate. Sensors and Actuators A: Physical, 334. https://www.sciencedirect.com/science/article/pii/S0924424721007937
Vo, T. N. A., & Chen, P. C. (2022). Maximizing Heterogeneous Bonding Strength Between PDMS/PMMA For Manufacturing Elastomer Microvalve System with High-Density Configuration. In Proceedings of IEEE MEMS 2022. https://ieeexplore.ieee.org/document/9699611
Huang, S., He, Q., Hu, X., & Chen, H. (2012). Fabrication of micro pneumatic valves with double-layer elastic poly(dimethylsiloxane) membranes in rigid poly(methyl methacrylate) microfluidic chips. Journal of Micromechanics and Microengineering, 22(8), 085008. https://doi.org/10.1088/0960-1317/22/8/085008
Dauson, E. R., Gregory, K. B., Greve, D. W., Healy, G. P., & Oppenheim, I. J. (2016). Mechanically robust microfluidics and bulk wave acoustics to sort microparticles. In SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring (Vol. 9805, Article 98051I). https://doi.org/10.1117/12.2214394
Surface Activation & Functionalization (Protein, Antifouling, Wettability)
Beyond enabling bonds, plasma is the chemical “on-ramp” for functional surfaces: it introduces reactive sites that allow EDC–NHS coupling, silane grafting, PEG/PVA stabilization, or selective fluorosilane modification. These downstream chemistries let designers control protein immobilization, prevent nonspecific adsorption, or lock in wettability contrasts. The literature emphasizes that plasma energy/time directly influence reactive group density (and thus the amount of immobilized biomolecule), and that pairing plasma with an appropriate stabilizing chemistry is often necessary to preserve desired surface behavior for the device’s lifetime.
Surface Activation & Funtionalization Articles
Sathish, S., Ishizu, N., & Shen, A. Q. (2019). Air plasma-enhanced covalent functionalization of poly(methyl methacrylate): High-throughput protein immobilization for miniaturized bioassays. ACS Applied Materials & Interfaces, 11, 46350–46360. https://doi.org/10.1021/acsami.9b14631
Subramanian, B., Kim, N., Lee, W., Spivak, D. A., Nikitopoulos, D. E., McCarley, R. L., & Soper, S. A. (2011). Surface modification of droplet polymeric microfluidic devices for the stable and continuous generation of aqueous droplets. Langmuir, 27(12), 7949–7957. https://doi.org/10.1021/la200298n
Xian, Z., Dai, P., Su, W., Xing, D., Sun, C., & You, H. (2023). Inhibition of non-specific protein adsorption on PMMA surface: The role of surface modification. Journal of the Saudi Chemical Society, 27. https://www.sciencedirect.com/science/article/pii/S131961032300159X
Lee, M., Oh, J., Lim, H., & Lee, J. (2021). Enhanced liquid transport on a highly scalable, cost-effective, and flexible 3D topological liquid capillary diode. Advanced Functional Materials, 31. https://doi.org/10.1002/adfm.202011288
Organ on a Chip & Multilayer Thermoplastic Devices
Multilayer PMMA and other thermoplastic organ-on-chip devices rely on plasma to produce uniform activation across stacked layers and to enable strong, biocompatible interlayer bonds. Plasma activation is frequently the step that precedes thermal fusion, adhesive lamination, silane coupling, or water-assisted microwave bonding in multilayer assembly workflows.
The following articles discuss how milder plasma doses and immediate chemical stabilization can preserve biocompatibility while delivering the sealing and mechanical integrity required for perfusion and long-term cell culture.
Organ on a Chip & Multilayer Thermopastic Device Articles
Paoli, R., Di Giuseppe, D., Badiola-Mateos, M., Martinelli, E., et al. (2021). Rapid manufacturing of multilayered microfluidic devices for organ on a chip applications. Sensors, 21(4), 1382. https://www.mdpi.com/1424-8220/21/4/1382
Hou, Y., Ai, X., Zhao, L., Gao, Z., Wang, Y., Lu, Y., Tu, P., & Jiang, Y. (2020). An integrated biomimetic array chip for high-throughput co-culture of liver and tumor microtissues for advanced anticancer bioactivity screening. Lab on a Chip, 20, 2482–2494. https://doi.org/10.1039/D0LC00288G
Hosic, S., Bindas, A., Puzan, M., Lake, W., Soucy, J. R., Zhou, F., Koppes, R. A., Breault, D. T., Murthy, S. K., & Koppes, A. N. (2020). Rapid prototyping of multilayer microphysiological systems. ACS Biomaterials Science & Engineering. https://doi.org/10.1021/acsbiomaterials.0c00190
Mehta, V., Vilikkathala Sudhakaran, S., & Rath, S. N. (2021). Facile route for 3D printing of transparent PETg-based hybrid biomicrofluidic devices promoting cell adhesion. ACS Biomaterials Science & Engineering, 7, 3947–3963. https://doi.org/10.1021/acsbiomaterials.1c00633
Narendran, G., Hoque, S. Z., Satpathi, N. S., et al. (2022). PDMS membrane-based flexible bi-layer microfluidic device for blood oxygenation. Journal of Micromechanics and Microengineering, 32. https://doi.org/10.1088/1361-6439/ac7ea6
Capillary PMMA Microfluidics
In capillary and blood-handling devices, plasma treatment is used primarily to produce the low contact angles required for reliable capillary pumping and to reduce nonspecific adsorption that would otherwise degrade assay performance. Studies show that plasma can reduce PMMA contact angle substantially (examples in the following set report drops from ~78° to ~38°) and that these changes translate to improved separation yields and stable capillary behavior. Plasma is also central to wettability-contrast strategies that combine hydrophilic channels with hydrophobic peripheries to manage bubbles and port-to-port interconnects.
Capillary PMMA Microfluidic Articles
Gao, Q., Chang, Y., Deng, Q., & You, H. (2020). A simple and rapid method for blood plasma separation driven by capillary force with an application in protein detection. Analytical Methods, 12, 2560–2570. https://doi.org/10.1039/D0AY00240B
Razunguzwa, T. T., Biddle, A., Anderson, H., Zhan, D., & Powell, M. (2009). Development of a microfluidics-based gel protein recovery system. Electrophoresis, 30(23), 4020–4028. https://doi.org/10.1002/elps.200900485
Xiao, Z., Sun, L., Yang, Y., Feng, Z., Dai, S., Yang, H., Zhang, X., et al. (2021). High-performance passive plasma separation on OSTE pillar forest. Biosensors, 11(10), 355. https://www.mdpi.com/2079-6374/11/10/355
Zhao, X., Ma, C., Park, D. S., Soper, S. A., et al. (2022). Air bubble removal: Wettability contrast enabled microfluidic interconnects. Sensors and Actuators B: Chemical, 361. https://www.sciencedirect.com/science/article/pii/S092540052200329X
Biosensing & Analytical PMMA Microfluidics
For biosensing and analytical microfluidics, plasma treatment is essential because it enables covalent capture chemistries and stable surface functionalization on PMMA. After activation, PMMA can be modified with EDC–NHS or other coupling reagents to immobilize proteins, antibodies or capture probes, and these chemistries underlie microfluidic immunoassays, MS-coupled platforms and fluorescence sensors.
Biosensing & Analytical PMMA Microfluidic Articles
Sathish, S., Ishizu, N., & Shen, A. Q. (2019). Air plasma-enhanced covalent functionalization of poly(methyl methacrylate): High-throughput protein immobilization for miniaturized bioassays. ACS Applied Materials & Interfaces, 11, 46350–46360. https://doi.org/10.1021/acsami.9b14631
Hu, H., Smith, S., Li, X., Qian, Z., Su, Y., Lin, M., Tu, J., & Liu, Y. (2020). Fast quantification of free amino acids in food by microfluidic voltage-assisted liquid desorption electrospray ionization–tandem mass spectrometry. Analytical and Bioanalytical Chemistry, 412, 1947–1954. https://doi.org/10.1007/s00216-020-02450-w
Remaud, P., Medlock, J., Das, A. A. K., Allsup, D. J., Madden, L. A., Nees, D., Weldrick, P. J., & Paunov, V. N. (2020). Targeted removal of blood cancer cells from mixed cell populations by cell recognition with matching particle imprints. Materials Chemistry Frontiers, 4, 197–205. https://pubs.rsc.org/en/content/articlehtml/2019/qm/c9qm00531e
Kosker, F. B., Aydin, O., & Icoz, K. (2022). Simple staining of cells on a chip. Biosensors, 12(11), 1013. https://www.mdpi.com/2079-6374/12/11/1013
Gao, Y., Pan, X., Xu, S., Liu, Z., Wang, J., Yu, K., Wang, C., Yuan, H., & Wu, S. (2020). Fluorescence-enhanced microfluidic sensor for highly sensitive in-situ detection of copper ions in lubricating oil. Materials & Design, 191, 108693. https://doi.org/10.1016/j.matdes.2020.108693
Conclusion
Plasma treatment is the foundational surface tool for making PMMA work reliably in microfluidics: it rapidly converts an inert, hydrophobic polymer into a wettable, chemically reactive surface that enables bonding, capillary flow, biofunctionalization and heterogeneous interfaces. The literature shows a wide range of effective recipes and successful application-specific workflows.