Laser-induced thermal bubbles for microfluidic applications.
ABSTRACT 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.
SourceAvailable from: Khashayar Khoshmanesh[Show abstract] [Hide abstract]
ABSTRACT: Recently, the bubble-based systems have offered a new paradigm in microfluidics. Gas bubbles are highly flexible, controllable and barely mix with liquids, and thus can be used for the creation of reconfigurable microfluidic systems. In this work, a hydrodynamically actuated bubble-based microfluidic system is introduced. This system enables the precise movement of air bubbles via axillary feeder channels to alter the geometry of the main channel and consequently the flow characteristics of the system. Mixing of neighbouring streams is demonstrated by oscillating the bubble at desired displacements and frequencies. Flow control is achieved by pushing the bubble to partially or fully close the main channel. Patterning of suspended particles is also demonstrated by creating a large bubble along the sidewalls. Rigorous analytical and numerical calculations are presented to describe the operation of the system. The examples presented in this paper highlight the versatility of the developed bubble-based actuator for a variety of applications; thus providing a vision that can be expanded for future highly reconfigurable microfluidics.Scientific Reports 04/2015; 5:9942. DOI:10.1038/srep09942 · 5.08 Impact Factor
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ABSTRACT: Payloads including FITC-Dextran dye and plasmids were delivered into NIH/3T3 fibroblasts using microbubbles produced by micro-second laser pulses to induce pores in the cell membranes. Two different operational modes were used to achieve molecular delivery. Smaller molecules, such as the FITC-Dextran dye, were delivered via a scanning-laser mode. The poration efficiency and the cell viability were both 95.1 ± 3.0 %. Relatively larger GFP plasmids can be delivered efficiently via a fixed-laser mode, which is a more vigorous method that can create larger transient pores in the cell membrane. The transfection efficiency of 5.7-kb GFP plasmid DNA can reach to 86.7 ± 3.3 %. Using this cell poration system, targeted single cells can be porated with high resolution, and cells can be porated in arbitrary patterns.Lab on a Chip 11/2014; 15(2). DOI:10.1039/C4LC00943F · 5.75 Impact Factor
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ABSTRACT: We present an optofluidic microvalve utilizing an embedded, surface plasmon-enhanced fiber optic microheater. The fiber optic microheater is formed by depositing a titanium thin film on the roughened end-face of a silica optical fiber that serves as a waveguide to deliver laser light to the titanium film. The nanoscale roughness at the titanium-silica interface enables strong light absorption enhancement in the titanium film through excitation of localized surface plasmons as well as facilitates bubble nucleation. Our experimental results show that due to the unique design of the fiber optic heater, the threshold laser power required to generate a bubble is greatly reduced and the bubble growth rate is significantly increased. By using the microvalve, stable vapor bubble generation in the microchannel is demonstrated, which does not require complex optical focusing and alignment. The generated vapor bubble is shown to successfully block a liquid flow channel with a size of 125 μm × 125 μm and a flow rate of ∼10 μl/min at ∼120 mW laser power.Biomicrofluidics 09/2014; 8(5):054126. DOI:10.1063/1.4900978 · 3.77 Impact Factor