ACOUSTIC BUBBLE PROPULSION AND ROTATION FOR MEMS DEVICES A Thesis by ONDER DINCEL (original) (raw)

Acoustically-actuated bubble-powered rotational micro-propellers

Sensors and Actuators B: Chemical, 2021

Bubble-powered acoustic microsystems span a plethora of applications that range from lab-on-chip diagnostic platforms to targeted interventions as microrobots. Numerous studies strategize this bubble-powered mechanism to generate autonomous self-propulsion of microrobots in response to high frequency sound waves. Herein, we present two micro-propeller designs which contain an axis-symmetric distribution of entrapped bubbles that vibrate to induce fast rotational motion. Our micro-propellers are synthesized using 3D Direct Laser Writing and chemically-functionalized to selectively trap air bubbles at their micro-cavities which function as propulsion units. These rotational acoustic micro-propellers offer a dual advantage of being used as mobile microfluidic mixers, and as autonomous microrobots for targeted manipulation. With regards to targeted manipulation, we demonstrate magneto-acoustic actuation of our first propeller design that can be steered to a desired location to perform rotational motion. Furthermore, our second propeller design comprises of a helical arrangement of bubble-filled cavities which makes it suitable for spatial micro-mixing. Our acoustic propellers can reach speeds of up to 400 RPM (rotations per minute) without requiring any direct contact with a vibrating substrate in contrast to the state-of-the-art rotary acoustic microsystems.

Propulsion of water-floating objects by acoustically oscillating microbubbles

International Journal of Precision Engineering and Manufacturing, 2011

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.

Acoustic driven microbubble motor device

Sensors and Actuators A: Physical, 2019

The graphical Abstract includes One Figure with its Caption Figure 2: The detailed design of AFMO motor device: a) Schematic diagram of CAD design for AFMO device with force internal cavities, b) Microscopic images of microbubbles trapped in the cavity when the device is submerged in water, c) Microscopic image of bubbles extracted from cavities and trapped at the entrance area when a specific acoustic wave is applied. d) Microscopic image of AFMO device rotating at a specific free-bubble oscillation frequency. Highlights  Acoustic Driven Microbubble Motor device is easy to fabricate  Lead to the fabrication of acoustic wave oscillation devices in 3D Technology  High speed and torque capability  All designing and operational techniques are provided

Manipulation of confined bubbles in a thin microchannel: Drag and acoustic Bjerknes forces

Physics of Fluids, 2011

Bubbles confined between the parallel walls of microchannels experience an increased drag compared to freestanding bubbles. We measure and model the additional friction from the walls, which allows the calibration of the drag force as a function of velocity. We then develop a setup to apply locally acoustic waves and demonstrate the use of acoustic forces to induce the motion of bubbles. Because of the bubble pulsation, the acoustic forces-called Bjerknes forces-are much higher than for rigid particles. We evaluate these forces from the measurement of bubble drift velocity and obtain large values of several hundreds of nanonewtons. Two applications have been developed to explore the potential of these forces: asymmetric bubble breakup to produce very well controlled bidisperse populations and intelligent switching at a bifurcation.

A bubble-powered micro-rotor: conception, manufacturing, assembly and characterization

A steady fluid flow, called microstreaming, can be generated in the vicinity of a micro-bubble excited by ultrasound. In this paper, we use this phenomenon to assemble and power a microfabricated rotor at rotation speeds as high as 625 rpm. The extractible power is estimated to be of the order of a few femtowatts. A first series of experiments with uncontrolled rotor shapes is presented, demonstrating the possibility of this novel actuation scheme. A second series of experiments with 65 µm rotors micromanufactured in SU-8 resin is then presented. Variables controlling the rotation speed and rotor stability are investigated, such as the bubble diameter, the acoustic excitation frequency and amplitude and the rotor geometry. Finally, an outlook is provided on developing this micro-rotor into a MEMS-based motor capable of delivering tunable, infinitesimal rotary power at the microscale. M This article features online multimedia enhancements (Some figures in this article are in colour only in the electronic version)

Manipulation of biological objects using acoustic bubbles: a review

Integrative and comparative biology, 2014

When a bubble oscillates in an acoustically driven pressure field, its oscillations result in an attractive force on micro-sized objects in the near field. At the same time, the objects are subject to a viscous drag force due to the streaming flow that is generated by the oscillating bubble. Based on these secondary effects, oscillating bubbles have recently been implemented in biological applications to control and manipulate micron-sized objects. These objects include live microorganisms, such as Caenorhabditis elegans and Daphnia (water flea), as well as cells and vesicles. Oscillating bubbles are also used in delivering drugs or genes inside human blood vessels. In this review paper, we explain the underlying physical mechanism behind oscillating bubbles and discuss some of their key applications in biology, with the focus on the manipulation of microorganisms and cells.

Onset of Particle Trapping and Release via Acoustic Bubble

Trapping and sorting of micro-sized objects is one important application of lab on a chip devices, with acoustic bubbles emerging as an effective, non-contact method. Acoustically actuated bubbles are known to exert a secondary radiation force ($\Fsr$) on micro-particles and stabilize them on the bubble surface, when this radiation force exceeds external hydrodynamic forces that act to keep the particles in motion. While the theoretical expression of Fsr\FsrFsr has been derived by Nyborg decades ago, no direct experimental validation of this force has been performed, and the relationship between Fsr\FsrFsr and the bubble's ability to trap particles in a given lab on a chip device remains largely empirical. In order to quantify the connection between the bubble oscillation and resultant Fsr\FsrFsr, we experimentally measure the amplitude of bubble oscillations that give rise to Fsr\FsrFsr and observe the trapping and release of a single microsphere in the presence of the mean flow at the corresponding acoustic parameters using an acoustofluidic device. By combining well-developed theories that connect bubble oscillations to the acoustic actuation, we derive the expression for the critical input voltage that particle release into the flow, in good agreement with the experiments.

Vibrational modes prediction for water-air bubbles trapped in circular microcavities

Physics of Fluids, 2018

Oscillating bubbles have proven to be a versatile tool for various microfluidic applications. Despite the existence of the extensive literature on the behavior of acoustically actuated bubbles, a ready-to-use approach, capable of predicting the oscillatory motion for the bubbles trapped in the circular microcavities, is still missing. In this study, we propose a theoretical model to quantify the resonant frequencies and viscous dissipation factors for a single trapped bubble and verify it experimentally. We further investigate an interaction of two coupled bubbles of equal and different radii. For the identical bubble pair, coupling results in controllable frequency shift from the modes of a single bubble, whereas the non-identical one can operate as a flow switch.