Laser-induced thermal bubbles for microfluidic applications

Department of Applied Physics and Materials Research Center, The Hong Kong Polytechnic University, Hong Kong, People's Republic of China.
Lab on a Chip (Impact Factor: 6.12). 02/2011; 11(7):1389-95. DOI: 10.1039/c0lc00520g
Source: PubMed


We present a unique bubble generation technique in microfluidic chips using continuous-wave laser-induced heat and demonstrate its application by creating micro-valves and micro-pumps. In this work, efficient generation of thermal bubbles of controllable sizes has been achieved using different geometries of chromium pads immersed in various types of fluid. Effective blocking of microfluidic channels (cross-section 500 × 40 μm(2)) and direct pumping of fluid at a flow rate of 7.2-28.8 μl h(-1) with selectable direction have also been demonstrated. A particular advantage of this technique is that it allows the generation of bubbles at almost any location in the microchannel and thus enables microfluidic control at any point of interest. It can be readily integrated into lab-on-a-chip systems to improve functionality.

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    • "The microfluidic particle image velocimetry (PIV) was a classical method for the flow rate detection [11], but the importation of a large amount of the trace microparticles may influence the features of biochemical reactions and was not preferred in the bio-microfluidic applications. Accompanied with the fast development of the lab-on-a-chip applications, there is an increasingly important and unmet need for the flow rate detection at the 10 nL/min to 10 μL/min range [12] [13] [14] [15]. In this letter we propose and demonstrate a new strategy by the optofluidic manipulation of a single microparticle for the flow rate detection in this range. "
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    ABSTRACT: Sensitive flow rate detection with a large dynamic range is highly desirable for the lab-on-a-chip applications. We demonstrate an optofluidic flow rate detection method based on the optical manipulation of a single microparticle by a cleaved single-mode fiber (SMF). The microbalance between the optical force and the flow force on the single polystyrene microparticle was used as a new strategy for the detection. Due to the inverse sensitivity, the limit of detection is pushed down to 20 nL/min by detecting the manipulation length as a function of the flow rate. The measurement range of about three orders of magnitude is achieved. The experimental results indicate that the method produces a good repeatability for the flow rate measurement. The cleaved SMF for the optofluidic manipulation also enables low cost, repeatable, and mass production of the sensing device.
    Full-text · Article · Dec 2015 · IEEE Photonics Technology Letters
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    • "Bubbles are now being used to reduce scattering cross section of modern submarines and new bubble-filled anechoic coating materials (metamaterial properties) are currently being developed [11]. In other applications, microbubbles are used as bioactive food ingredients, green adjuncts for water or surface cleaning [12] [13] [14] [15], ultrasound contrast agents [16] [17] [18] [19] [20] and as efficient pumps or activators in the field of microtechnology [21]. "
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    ABSTRACT: Single bubble sizing is usually performed by measuring the resonant bubble response using the Dual Frequency Ultrasound Method. However, in practice, the use of millisecond-duration chirp-like waves yields nonlinear distortions of the bubble oscillations. In comparison with the resonant curve obtained under harmonic excitation, it was observed that the bubble dynamic response shifted by up to 20 percent of the resonant frequency with bubble radii of less than 100 μm. In the case of low pressure waves (View the MathML source), an approximate formula for the apparent frequency shift is derived. Simulated and experimental bubble responses are analyzed in the time–frequency domain using an enhanced concentrated (reassigned) spectrogram. The difference in the resonant frequency resulted from the persistence of the resonant mode in the bubble response. Numerical simulations in which these findings are extended to pairs of coupled bubbles and to bubble clouds are also presented.
    Full-text · Article · Nov 2015 · Journal of Sound and Vibration
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    ABSTRACT: This paper describes a micro-pumping technology using laser induced thermal bubbles, which offers greater flexibility for selective control of flow directions in microfluidic chips. Without complicated fabrication, the bubble in the microchannel could be created by focusing a continuous-wave laser onto the patterned metal pad. Experiments demonstrate that the flow direction can be freely chosen at a T-junction and the flow velocity could be adjusted from 100 to 400 μm/s in real time by adjusting the laser power. This technology can be readily incorporated into the lab-on-a-chip systems for flexible microfluidic manipulation.
    No preview · Article · Jan 2011
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