Fig. 1.

Schematic diagrams of tandem bubble generation, jet formation, and resultant flow interaction with a single cell grown nearby in a microfluidic channels. (A) Experimental setup. Two Nd:YAG lasers (laser 1 and laser 2) are projected through a 63X objective (path shown in green) and focused onto a pair of gold dots (6 µm in diameter and 15 nm in thickness) coated on the glass substrate of the microchannel, separated by an interbubble distance (d_IB) of 40 µm. Two high-speed video cameras: a Shimadzu HPV-X (camera 1) and a Phantom v7.3 (camera 2) are used to record bubble–bubble–cell interaction when the fluorophore cube with a dichroic mirror (DM1) is off the light path and the beam splitter (BS1) is at 80/20 position. Thereafter, the fluorophore cube is switched back with BS1 at 0/100 position for fluorescent imaging (path shown in red) using a Zeiss AxioCam MRc 5 (camera 3) and a Xenon light source (Lamp). Imaging acquisition with camera 2 or 3 (path shown in black) is controlled by a rotating mirror (RM) underneath BS1. (B) Illustration of the dynamic interaction of tandem bubbles and the resultant deformation of a target cell (shown in dashed line). Bubble–bubble–cell interaction is conducted in the microchannel with dimension of 800 × 25 µm. Single HeLa cells are confined and grown within a 32 × 32 µm island coated with fibronectin. Two fibronectin coated patterns are used, namely H-0° and H-90°, corresponding, respectively, to the case where the proximal edge of the adherent cell is firmly attached onto the substrate or free standing. The standoff distance (S_d) between the leading edge of the cell and the center of the closer gold dot is varied from 10 to 40 µm in different units of the gold-dots/fibronectin island distributed inside the microfluidic channel for high-throughput experiments.