Surface activation of poly(methyl methacrylate) for microfluidic device bonding through a H₂O plasma treatment linked with a low-temperature annealing

Abstract

This paper reports on a rapid, lossless process for the bonding of poly(methyl methacrylate) (PMMA) substrates for use in microfluidic devices for blood tests, utilizing H2O plasma, and H2O linked rapid thermal annealing (RTA) treatments. The bonding of PMMA produced with H2O plasma linked with RTA was analyzed, and its effect on the bonding of free radicals was investigated. The PMMA surface treatment was performed at constant RF power and H2O vapor flow but changing plasma treatment times in both processes. The surface modification of the PMMA subjected to the H2O plasma treatment was studied by optical emission spectroscopy, which confirmed that the relative intensity of hydroxyl radicals and oxygen emission peaks. The surface of the PMMA after being subjected to the plasma linked with RTA treatment was also characterized. The free energy increased with the plasma treatment time. The tensile test results revealed that the strength of OH bonds on the PMMA surface increased with a high plasma treatment time of 120 s. After bonding, UV–visible transmission spectrum measurements revealed that the transparency of the microfluidic device increased. We demonstrated the bonding of a microfluidic device with plasma treatment without deformation. This method provides an ideal bonding technique for the manufacture of microfluidic devices with PMMA. This technique has more advantages than other bonding techniques.

Recent Advances in Thermoplastic Microfluidic Bonding

“…Song et al used oxygen plasma treatment followed by annealing for reversible adhesion of PDMS with PS for microfluidic cell culture applications [ 85 ]. H 2 O plasma treatment followed by Rapid Thermal Annealing (RTA) was used to bond PMMA based microfluidic devices [ 86 ]. Terai et al used water-vapor-assisted plasma treatment in the adhesion of COP and glass substrates, which also helped to maintain stable superhydrophilicity i.e., water contact angle <1° [ 87 ].…”

Atmospheric micro-sized cold plasma jet created by a long and ultra-flexible generator with sputtered gold thin film electrode

“…Besides, highly reactive species such as OH (A 2 ∑ + (ν ′ = 0)→X 2 ∏(ν ′′ = 0), 309.1 nm), the oxygen atoms (O, 3p 5 P→3s 5 S, 777.1 nm; 3p 3 P→3s 3 S, 844.4 nm) were also detected, and they were created through the dissociation of oxygen molecules and water vapor molecule by electrons and He metastables [47]. These highly reactive species such as OH at 309.1 nm and atomic O at 777.1 nm and 844.4 nm are considered to be the most effective species in the plasma and play key roles in endoscopic therapies or organic materials applications [6,38].…”

“…The common feature of the aforementioned flexible plasma jet generators is that they all used the plastic tube with inner diameters of about several millimeters, which is unable to be used in some precise treatment applications, such as a single cell therapy. Therefore, it is necessary to use the tubes with much smaller diameter, such as the groups of Kim et al and Zuo et al developed a flexible microplasma jet device using a hollow optical fiber with inner diameter of tens to hundreds microns [35][36][37], and Wen et al reported a cantilever arrays with nano aperture hollow tips for parallel microplasma etching [38]. The generated microplasma can be used to precisely treat a cancer cell or target to a desired site.…”

Bonding Strategies for Thermoplastics Applicable for Bioanalysis and Diagnostics

“…With the use of plasma, the bonding temperature was decreased from 100 to 85 • C due to a lower Tg at the surface of polymers after plasma treatment, and the fracture of copper microelectrodes was eliminated. Adapting to the same concept, Immanuel et al also introduced surface activation through H 2 O plasma treatment linked with low-temperature annealing for bonding PMMA devices for blood tests [53].…”