A unique solution for preventing clogging of flow channels by gas bubbles

Kohnle, J.; Waibel, G.; Cernosa, R.; Storz, M.; Ernst, H.; Sandmaier, H.; Strobelt, T.; Zengerle, Roland

doi:10.1109/memsys.2002.984094

Cited by 19 publications

(25 citation statements)

References 3 publications

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“…The structure sketched in Fig. 1 has been presented first in Kohnle et al (2002), where it was termed channel in channel (CHIC). In the current work it will be referred to as T-shaped channel.…”

Section: Introductionmentioning

confidence: 99%

Static and dynamic behaviour of gas bubbles in T-shaped non-clogging micro-channels

Litterst

Metz

Zengerle

et al. 2008

Microfluid Nanofluid

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Preventing micro-channels from clogging is a major issue in most micro and nanofluidic systems (Gravesen et al., J Micromech Microeng 3(4):168-182, 1993; Jensen et al., In: Proc. of MicroTAS 2002, Nara, Japan, pp 733-735, 2002 Wong et al., J Fluid Mech 292:71-94, 1995). The T-shaped channel first reported by Kohnle et al. (In: IEEE MEMS, the 15th international IEEE micro electro mechanical conference (ed), Las Vegas, pp 77-80, 2002) prevents micro-channels from clogging by the aid of the equilibrium bubble position in such a geometry. This work is concerned with the static and dynamic behaviour of bubbles in such T-shaped microchannels. The aspect ratio of a rectangle enclosing the Tshaped channel and the contact angle of the walls are the main parameters influencing the static and dynamic bubble behaviour. It is investigated in this article how these parameters relate to the equilibrium bubble shape and how optimum bubble velocities can be achieved inside the channel. An analytical model depending on the contact angle and the channel geometry is presented that allows to determine the bubble configuration inside the channel by minimizing the bubble's surface energy. A second model is derived to predict the velocity of gas bubbles driven by buoyancy in vertical T-shaped channels. The model is applied to design T-shaped channels with a maximum mobility of gas bubbles. Experiments with MEMS fabricated devices and CFD simulations are used to verify the models. Furthermore design rules for an optimum nonclogging channel geometry which provides the highest gas bubble mobility are given.

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Section: Introductionmentioning

confidence: 99%

Static and dynamic behaviour of gas bubbles in T-shaped non-clogging micro-channels

Litterst

Metz

Zengerle

et al. 2008

Microfluid Nanofluid

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“…Most of the previous studies attributed the lack of motion of stagnant bubbles to resistant capillary forces related to pressure differences across the front and back interfaces [2,[13][14][15][16][17]. Herein, we investigate pinning forces along triple contact lines as another factor hindering the motion of dry bubbles.…”

Section: Introductionmentioning

confidence: 95%

“…The emergence of the bubbles can be caused by various factors, e.g., simply by diffusion of air into the device or by the degassing of the liquid due to temperature or pressure variations. Vibration can stimulate the formation of the bubbles as well [2]. Bubbles can also get introduced into the system while connecting or disconnecting tubing to the valves, pumps, etc.…”

Section: Introductionmentioning

confidence: 99%

The Role of Contact Line (Pinning) Forces on Bubble Blockage in Microchannels

Mohammadi

Sharp

2015

Journal of Fluids Engineering

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This paper highlights the influence of contact line (pinning) forces on the mobility of dry bubbles in microchannels. Bubbles moving at velocities less than the dewetting velocity of liquid on the surface are essentially dry, meaning that there is no thin liquid film around the bubbles. For these "dry" bubbles, contact line forces and a possible capillary pressure gradient induced by pinning act on the bubbles and resist motion. Without sufficient driving force (e.g., external pressure), a dry bubble is brought to stagnation. For the first time, a bipartite theoretical model that estimates the required pressure difference across the length of stagnant bubbles with concave and convex back interfaces to overcome the contact line forces and stimulate motion is proposed. To validate our theory, the pressure required to move a single dry bubble in square microchannels exhibiting contact angle hysteresis has been measured. The working fluid was deionized water. The experiments have been conducted on coated glass channels with different surface hydrophilicities that resulted in concave and convex back interfaces for the bubbles. The experimental results were in agreement with the model's predictions for square channels. The predictions of the concave and convex back models were within 19% and 27% of the experimental measurements, respectively.

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“…A narrow channel parallel to a wide channel was designed to bypass bubbles because bubbles tend to stay in a wide channel due to their surface tension (Kohnle et al 2002). Unltrasonic wave was used to degas bubbles in a microreactor, and a hydrophobic microchannel was connected to the microreactor to release bubbles while preventing the leak of water (Yang et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Micro/nanoporous membrane based gas–water separation in microchannel

Zhu

2009

Microsyst Technol

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In this paper, a method coupling micro/nanoporous membranes with microchannels for the gas/water separation in microscale has been demonstrated. The principle of separation is based on the basic properties of membranes-wetted micro/nanoporous hydrophilic membranes can block gas due to a large water surface tension in the entrance of micro/nano pores to withstand the gas pressure, while it allows water to permeate with overcoming the flow resistance of pores; in contrast, hydrophobic membranes permit gas to penetrate but prevent water flow. These two kinds of membranes coupled with microchannels in cross-flow mode or dead-end mode can separate gas/water in microscale. The separation in crossflow mode can achieve relative high water permeate flow rate, while the separation in dead-end mode can completely separate gas/water segments in a single operation step. The membrane-based separation method has low cost, easy integration into microfludics channels, design flexibility with two configuration modes (cross-flow and dead-end).

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A unique solution for preventing clogging of flow channels by gas bubbles

Cited by 19 publications

References 3 publications

Static and dynamic behaviour of gas bubbles in T-shaped non-clogging micro-channels

Static and dynamic behaviour of gas bubbles in T-shaped non-clogging micro-channels

The Role of Contact Line (Pinning) Forces on Bubble Blockage in Microchannels

Micro/nanoporous membrane based gas–water separation in microchannel

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