An integrated microfluidic chip for generation and transfer of reactive species using gas plasma

Abstract

Reactive species produced by atmospheric-pressure plasma (APP) are useful in many applications including disinfection, pretreatment, catalysis, detection and chemical synthesis. Most highly reactive species produced by plasma, such as ·OH, 1O2 and $$ {\text{O}}_{2}^{ \cdot - } $$O2·-, are short-lived; therefore, in situ generation is essential to transfer plasma products to the liquid phase efficiently. A novel microfluidic device that generates a dielectric barrier discharge (DBD) plasma at the gas–liquid interface and disperses the reactive species generated using microbubbles of ca. 200 µm in diameter has been developed and tested. As the bubble size affects the mass transfer performance of the device, the effect of operating parameters and plasma discharge on generated bubbles size has been studied. The mass transfer performance of the device was evaluated by transferring the reactive species generated to an aqueous solution containing dye and measuring percentage degradation of the dye. Monodisperse microbubbles (polydispersity index between 2 and 7%) were generated under all examined conditions, but for gas flow rate exceeding a critical value, a secondary break-up event occurred after bubble formation leading to multiple monodisperse bubble populations. The generated microbubble size increased by up to ~ 8% when the device was operated with the gas plasma in the dispersed phase compared to the case without the plasma due to thermal expansion of the feed gas. At the optimal operating conditions, initial dye concentration was reduced by ~ 60% in a single pass with a residence time of 5–10 s. This microfluidic chip has the potential to play a significant role in lab-on-a-chip devices where highly reactive species are essential for the process.

Epoxidation of trans-stilbene in a microfluidic plasma reactor

“…The volume of gas contained in these bubbles were too large to maintain a spherical shape inside the reaction chamber, which has a channel height of 100 µm, hence the bubbles were squashed between the top and the bottom walls. It was considered that the shape of the bubbles within this microchip are symmetrical ellipsoid (oblate spheroid), which was described in our previous study [32]. In our previous work, a dense cloud of microbubbles was produced in water containing the surfactant vinyl alcohol, and it was possible to generate microbubbles ~140 µm in diameter.…”

“…The details of the microfluidic plasma reactor used in this study is presented elsewhere [32]. A brief description is provided here for completeness.…”

“…Scheme 2: He/O2 atmospheric-pressure plasma epoxidation and ozonolysis of trans-stilbene [25] The main purpose of this study was to carry out trans-stilbene epoxidation using a novel DBD plasmamicrobubble reactor developed recently [32] that generates a DBD plasma at the vicinity of the microbubble generation site and disperses the reactive species generated via monodisperse microbubbles. The main reactive oxygen species (ROS) generated from the He/O2 admixtures supplied to the microchip were O3, O, and 1 O2 [33][34].…”

Microfluidic plasmas: Novel technique for chemistry and chemical engineering

“…Research conducted by Ogunyinka et. al developed a plasma integrated microfluidic chip based on the DBD concept, where the plasma power was measured by the Lissajous method [80].…”

Electrodeless atmospheric secondary induced ionization jet (EASII-jet): Dynamics and properties of a transferred helium plasma source

“…Many applications rely on this plasma reactivity in catalysis and materials science processes 3,4 . More generally, APPJs are involved in a large panel of applications such as in medicine to stimulate biological responses 5,6 , agriculture 7 and liquid activation 8,9 . Beyond the non-equilibrium reactive chemistry, APPJs generate guided ionization waves 10 (IWs) -guided streamers 11 -driven by a high electric field (EF) ahead of the discharge channel 12,13 .…”