An approach of bubble generation and manipulation by using the photothermal effects of laser irradiation on light absorbing particles

Abstract

The photothermal effects have shown the possibilities for applications in optical manipulation. In this paper, an approach is demonstrated to generate and manipulate a bubble using the photothermal effects. First, a high-power laser is used to irradiate the light absorbing particles for creating a microbubble. The bubble grows up to a diameter of a few hundred micrometers in several seconds due to the diffusion of dissolved gases. The bubble does not float up and is confined at the lower boundary of the sample cell by the thermocapillary force. The force is induced by laser heating of the particles at the bubble base. Second, the bubble can be manipulated following the laser focal spot. The bubble is dragged by the horizontal component of thermocapillary force. The bubble re-grows as it moves because it absorbs the dissolved gases in its migration path. The bubble floats up finally when it grows up to the maximum size. The perpendicular component of thermocapillary force can be estimated equal to the buoyancy of the floated bubble and is about 38 nN at the laser power of 130 mW. Furthermore, we show the generation and manipulation of the bubbles in a capillary. The reason for the decrease in movement velocity in the capillaries has been studied and discussed. The approach of bubble manipulation shows a potential application in transporting the microparticles.

Experimental Study of Transverse Trapping Forces of an Optothermal Trap Close to an Absorbing Reflective Film

“…Over recent decades, optothermal manipulation techniques [1][2][3][4] have become useful tools for manipulating micro-objects such as microparticles [5][6][7][8][9][10][11][12], or microbubbles [13][14][15][16][17], etc. The optothermal methods manipulate the micro-objects by exerting the optothermal forces, which are based on various light-induced thermal processes [1] such as Marangoni convection [18], thermophoresis [19], thermophoretic depletion [20], thermoelectricity [21][22][23], and photophoresis [24][25][26].…”

Optothermal Microparticle Oscillator Induced by Marangoni and Thermal Convection

“…Further increasing the laser power and reducing the distance between the heating spot and the bubble can increase the temperature gradient on the bubble surface, inducing stronger Marangoni convection, which can cause the collected particle to adhere to the bubble surface. 32 Furthermore, we illustrate that the value of D min varies with laser power, as shown in Figure 4b. It is apparent that D min increases with increasing laser power.…”

Growth of Laser-Induced Microbubbles inside Capillary Tubes Affected by Gathered Light-Absorbing Particles

“…The current studies show that bubble formation is caused by the evaporation of water that reaches boiling point upon laser illumination. Additionally, the bubble growth is dominated by the diffusion of dissolved gases after the microbubble is created [ 22 , 38 , 39 ].…”