Search

This paper designs an input class that provides the data necessary for the test to reduce the time and inconvenience caused by the frequent input of test data in the debugging process after programming. Using the test-driven development concept, test data is provided using equivalence partitioning and boundary value analysis of black-box test.

This paper describes a novel non-invasive micromanipulation technique that employs the cavitational microstreaming generated by acoustically oscillating twin bubbles. First, a single acoustically oscillating bubble was attached to the tip of a rod that was combined with a three-dimensional traverse system, and a fish egg (diameter: 1 mm) was then manipulated in an aqueous medium. Although the microstreaming generated by the single oscillating bubble was sufficiently strong to push and move the fish egg, the manipulation direction was uncontrollable. Hence, to improve the manipulation controllability, identical twin bubbles with the same size and resonant frequency were employed. The identical gas bubbles were generated on a microfabricated chip comprising sharp tip-shaped electrodes by employing an electrochemical method, electrolysis, and controlling the applied voltage and time. Subsequently, the bubbles were sequentially transferred to the tips of a U-shaped rod coated with a hydrophobic layer to improve the surface adhesion. The force generated from the acoustically oscillating bubbles and its direction were analyzed under various acoustic excitation conditions by using high-speed images. Our results showed that the generated force was proportional to the bubble oscillation amplitude, whereas the direction of the force depended on the distance between a bubble and object. A steel ball (500 μm diameter) was used for investigating the force direction. When a bubble (600 μm diameter) was acoustically excited, the steel ball was pulled toward the oscillating bubble when the distance between the bubble and ball was short ( 3 mm). Finally, a fish egg (diameter: 1 mm) and glass beads (diameter: 100 μm) were experimentally manipulated using acoustically oscillating twin bubbles.

This paper describes a novel microfluidic mixing method using an alternating current electrowetting-on-dielectric (AC-EWOD)-driven mobile oscillating bubble. An AC-EWOD-driven bubble can generate a microstreaming flow and be simultaneously transported on the two-dimensional surface of patterned electrodes covered with a hydrophobic dielectric layer in a microfluidic chip filled with an aqueous medium. When a bubble is actuated by AC-EWOD at a certain frequency (100 Hz), it oscillates and simultaneously generates a microstreaming flow around itself owing to its compressibility. The flow induced by the bubble oscillation is strong enough to be applied for enhancement of fluid mixing. The oscillating bubble also can be transported on the array of EWOD electrodes using the same AC-EWOD actuation. The bubble behavior under different AC-EWOD conditions has been investigated, and the bubble oscillation amplitudes are characterized by using a high-speed camera. The flow visualization experiments show that the strength of the microstreaming flow is proportional to the bubble oscillation amplitude. For a relative comparison of mixing enhancement, four cases with different combinations of the two actuations (bubble oscillation and transportation) have been tested; the results show that a bubble simultaneously actuated by both actuations shows overwhelming mixing performance with reduced mixing time. This method can be applied to efficient mixing tools in microfluidic systems, with the benefits of a small size and high compatibility.

In this paper, novel propulsion of micro/millimeter-sized water-floating objects has been experimentally demonstrated. When an acoustic wave propagates onto air bubbles in a liquid medium, the bubbles oscillate and generate cavitational microstreaming flows; this can be used to propel small water-floating objects. This propulsion concept is simple, but the propulsion can provide sufficient force to propel the water-floating objects without electrical connecting wires and mechanical moving parts. In this study, we prepared open-box-type micro/millimeter-sized objects using a thin Al film. We then experimentally realized linear and rotational motions and two-dimensional maneuvers on the surface of water. The effects of the frequency of the acoustic wave and the applied voltage on the motions are quantified with the bubble oscillation amplitude using high speed images. Such water-floating objects propelled by oscillating microbubbles can be integrated with cameras and sensors and used in environment monitoring systems or surveillance security systems.

This paper describes a novel tweezing system using cavitational microstreaming flows generated by acoustically oscillating twin bubbles for non-contact micromanipulation. A tweezing system with a single acoustically oscillating bubble attached on the tip of a rod integrated with a three-dimensional traverse system is firstly tested to manipulate a fish egg (1 mm diameter) in an aqueous medium. Although the flow generated from the single oscillating bubble is strong enough to push and move the fish egg, the moving direction of the fish egg is not controllable. To improve the control of the manipulation, identical twin bubbles, which have the same size and resonant frequency, are applied. To obtain the identical bubbles, an electrolysis chip consisting of sharp tip-shaped electrodes is microfabricated, and each bubble is generated from the chip by controlling the applied voltage and time and then transported to the tips of a U-shaped rod. Manipulation of a fish egg (1 mm diameter) and glass beads (100 µm diameter) is experimentally demonstrated using acoustically oscillating twin bubbles. Using a high speed camera, the force generated by the acoustically oscillating bubbles and its direction are analyzed in various acoustic excitation conditions. The results show that the generated force is proportional to the bubble oscillation amplitude, and the direction of the force depends on the distance between a bubble and object. A steel ball (500 µm diameter) is used for the investigation of the force direction. When a bubble (600 µm diameter) is acoustically excited, the steel ball is pulled into the oscillating bubble in the short distance (