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.

Light and Particle Manipulation Based on Optothermal Surface Bubbles

“…The position, size, and shape of the OSB can be precisely and dynamically changed by modulating the laser beam. Therefore, the OSB enables many intriguing applications ranging from the micro/nanomanipulation of fluids [1,2], particles [3,4], cells [5], and light [6] to the synthesis of micro/nano-structures under ambient conditions [7]. Here, we demonstrate how an OSB can be used to dynamically control light and particles.…”

Size control of vapor bubbles on a silver film by a tuned CW laser

“…Actually, the bubble can be regarded as an inverse structure of droplet, which can be used as a tunable microlenses. 17,18 Secondly, the vapor bubble can be used as a bubble valve, which can be applied to controlling microfluids in channels or biochips [19][20][21] Another useful application reported recently by us, 22 is to manipulating the microparticles with the laser induced bubble. The microparticles can be attracted to bubble through strong convection flow.…”

Optofluidic microvalve-on-a-chip with a surface plasmon-enhanced fiber optic microheater

“…More importantly, since the fiber guided laser power is mostly absorbed in the titanium film, the laser irradiation to the sample fluids will be minimal, which makes the device a safe choice for the manipulation of biological samples. In addition, unlike other microfluidic devices demonstrated for laser bubble generation, 3,19 there is no need for metal film deposition on substrates for chip fabrication, which allows for flexible chip design and simple fabrication with only polymer processes.…”

“…Electronic mail: mmyu@umd.edu typically used as mediums in microfluidic chips for converting optical energy to thermal energy. 3,19 However, the large optical power loss due to the light transmission through the optical path to the light absorbing medium is inevitable. Furthermore, the unwanted exposure of laser to the sample fluids poses another potential limitation, which can be especially harmful for biological samples.…”