On-chip separation method using a bubble for bio/micro-object manipulation

A novel on-chip bubble-separator has been developed where microparticles in an aqueous medium are separated and collected by size using an acoustically excited bubble as a mechanical filter. The concept of the bubble-separator is experimentally verified: bubble manipulation (generating and transporting operations) and micro-object manipulation (selectively capturing, carrying, and releasing operations). Optically induced bubble generation is firstly tested for different optical powers in a microfluidic chip with an amorphous silicon layer as an optically absorbent material. And bubble transportation is also demonstrated using optically induced thermocapillary effects. Micro-object manipulation is separately demonstrated using a bubble with two different sized glass and polystyrene particles in an aqueous medium. When a bubble is acoustically excited by a piezoactuator attached on the side of a chip, it oscillates and simultaneously captures large microparticles owing to the oscillating bubble induced radiation force but repels small microparticles due to the bubble induced cavitational microstreaming. Finally, the manipulation (separation and collection) of the mixture of two different sized glass particles is achieved using a bubble actuated by optical and acoustical excitation.