Formation of monodisperse bubbles in a microfluidic flow-focusing device - Applied Physics Letters 85, Number 13

Aug 25, 2026

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Applied Physics Letters presents a microfluidic flow-focusing method for generating monodisperse gaseous bubbles on a chip. The approach covers bubble diameters from 10 to 1000 µm and links bubble volume to gas pressure, liquid flow rate, and liquid viscosity through a scaling relation. It enables simultaneous, independent control of bubble size and dispersed-phase volume fraction. Under suitable conditions, bubbles self-assemble into ordered flowing lattices, with lattice structures tunable by adjusting flow parameters.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages3

Reading Time8 min

AccessFree to download

Method and scaling for monodisperse bubble generation

Bubble formation mechanism in the flow-focusing oriﬁce

Control parameters: size and volume fraction

Self-assembly into ordered lattices

APPLIED PHYSICS LETTERS VOLUME 85, NUMBER 13 27 SEPTEMBER 2004 Formation of monodisperse bubbles in a microﬂuidic ﬂow-focusing device Piotr Garstecki, Irina Gitlin, Willow DiLuzio, and George M. Whitesidesa) Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts Eugenia Kumacheva Department of Chemistry, University of Toronto, Toronto, Ontario, Canada Howard A. Stone Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts (Received 29 March 2004; accepted 21 July 2004) This letter describes a method for generating monodisperse gaseous bubbles in a microﬂuidic ﬂow-focusing device. The bubbles can be obtained in a range of diameters from 10 to 1000 mm. The volume Vb of the bubbles scales with the ﬂow rate q and the viscosity m of the liquid, and the pressure p of the gas stream as Vb ~p/ qm. This method allows simultaneous, independent control of the size of the individual bubbles and volume fraction of the dispersed phase. Under appropriate conditions, bubbles self-assemble into highly ordered, ﬂowing lattices. Structures of these lattices can be adjusted dynamically by changing the ﬂow parameters. © 2004 American Institute of Physics. [DOI: 10.1063/1.1796526] This letter describes a microﬂuidic method for a direct on-chip generation of monodisperse gaseous bubbles with simultaneous and independent control over the size of the bubbles and volume fraction of the dispersed phase. Microﬂuidic devices are becoming important for applications in on-chip separation, 1–3 high-throughput screening,4 protein crystallization,5,6 and kinetic analysis.7,8 These devices require the control of small volumes of ﬂuids, and the understanding of multiphase ﬂows. Liquid-liquid dispersions have been generated via a number of methods, including both geometry-dominated breakup9,10 and ﬂow-dominated rupturing.11–16 Less work has dealt with gas-liquid dispersions. For example, Ganan-Calvo et al.17 described the formation of monodisperse gas bubbles in capillaries. They reported a high Reynolds number scaling that is independent of the ﬂuid viscosity. Here, we describe a ﬂow-focusing device incorporated directly into a microﬂuidic chip and capable of delivering bubbles at frequencies exceeding 105 bubbles per second. In a wide range of ﬂow parameters the polydispersity index s, deﬁned as the standard deviation of the volume of the bubble divided by the mean volume, is ,2% . In our system viscous effects are important. It operates at low-tomoderate Re 18 and is therefore compatible with conditions of microﬂuidic devices. We fabricated the ﬂow-focusing devices 12 (Fig. 1) using soft lithography. 19,20 We assembled the devices by placing Polydimethylosiloxane (PDMS_ stamps in contact with glass cover slides. We ﬁlled the channels with water immediately after sealing to ensure the hydrophilic character of the walls of the microchannels.20 The contact angle of aqueous solutions used in our study on freshly oxidized PDMS was less than 30° . We supplied nitrogen through the gas inlet channel from a pressurized tank via a pressure-reduction valve. The liquid was pumped using a digitally controlled syringe pump (Harvard Apparatus PhD2000) . We used three different liquids: pure water (viscosity m = 0.92 mPa) and two aqueous solutions of glycerol, 52% sw/wd sm = 6 . 1 mPad and 62% sw/wd sm = 10 . 84 mPad.21 Apart from one set of experiments, all of the a)Electronic mail: [gwhitesides@gmwgroup.harvard.edu](gwhitesides@gmwgroup.harvard.edu) liquids also contained 2 % sw/wd Tween-20 surfactant. After changing any of the ﬂow parameters, we allowed at least 60 s of equilibration time. We used a Nikon camera to capture still images and Phantom high-speed cameras to capture movies (capturing frame rates up to 160 kHz) . We used homemade image analysis software to measure the areas of the interface between the bubbles and the top wall of the channel. We calcul

FAQs

What does the microfluidic flow-focusing device achieve in the paper?

It enables direct on-chip generation of monodisperse gaseous bubbles with independent control of bubble size and the dispersed-phase volume fraction.

How is bubble volume related to flow and material properties?

The bubble volume Vb follows a scaling with gas pressure p, liquid flow rate q, and liquid viscosity µ (Vb ~ p/(qµ)).

What happens to bubbles under appropriate conditions?

Bubbles self-assemble into highly ordered, flowing lattices whose structures can be adjusted dynamically by changing flow parameters.

Aug 25, 2026

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