Keynote Speakers

ACOUSTIC CONTROL OF SORTING AND FLUID INJECTION IN MICROFLUIDIC DEVICES
David Weitz
Harvard University, USA

This talk will discuss the use of surface acoustic waves to sort fluids and inject fluids into drops in a controlled manner. The use of these techniques for biotech applications will be discussed.

ACOUSTIC LEVITATION: FASTER, HIGHER, STRONGER
Bruce Drinkwater
University of Bristol, UK

The talk will describe the authors work on acoustic levitation and set this in the context of the state of the art in this field. The talk will then discuss the limits of acoustic levitation. What forces can be applied, what objects can be manipulated, and how fast can they be moved. Limitations imposed by physics will be discussed, as will be those due to currently available equipment.

MECHANICS AND EXPERIMENTAL DYNAMICS: FROM ACOUSTOFLUIDICS TO GRAVITATIONAL INTERACTION
Jürg Dual
ETH Zürich, SWITZERLAND

The talk will start with some highlights from 20 years of acoustofluidics at ETH including analytical, experimental and numerical aspects. Then a new laboratory experiment will be presented, where gravitational interaction between a transmitter (bending beam or two rotating rods) and a detector (High Q resonator) is demonstrated. This fully characterized experiment explores gravitational effects at black hole merger frequencies (~40Hz). ( Nature Physics, 2022; doi: 10.1038/s41567-022-01642-8)

HEARING IS BELIEVING: CORRELATING OPTICAL AND ACOUSTIC IMAGING OF BUBBLE DYNAMICS IN A MICROFLUIDIC SYSTEM
Eleanor Stride
University of Oxford, UK

Ultrasound driven microbubbles offer enormous potential for the targeted delivery of a range of therapies. Developing safe and effective treatment monitoring protocols, however, presents a significant challenge. This is due to the complexity of microbubble dynamics and the corresponding range of acoustic emissions. To address this challenge we have developed a microfluidic system in which both individual and clusters of microbubbles can be exposed to ultrasound and their behaviour captured simultaneously using ultra-high-speed optical imaging (1-10 MHz) and passive acoustic mapping.


Invited Speakers

EXPLOITING ACOUSTIC FIELD-MICROSWIMMER INTERACTIONS TO ACCELERATE ACOUSTOFLUIDIC DEVICE DEVELOPMENT
Mark Meacham
Washington University in St. Louis, USA

Our group has reported use of motile C. reinhardtii algae cells to identify optimal resonant frequencies of operation and to qualitatively map the strength of the acoustic field in one- and two-dimensional bulk acoustic wave (BAW) devices. We have also extended the method to quantify the acoustic energy density in simple straight microchannels, achieving agreement within 1% to a standard method based on passive particle tracking. In this talk, I will revisit these results while also presenting new applications involving surface acoustic wave (SAW) devices. By deploying a real-time experimental measurement tool, we hope to improve the operational stability of acoustofluidic technologies, accelerating their adoption in emerging clinical and industrial applications.

STANDING WAVE ACOUSTOPHORESIS OF LEGIONELLA SPECIES AND THE INFLUENCE OF MULTIBODY EFFECTS
Alen Pavlič
ETH Zürich, SWITZERLAND

Acoustic manipulation of small objects such as bacteria in a standing wave is challenging due to the acoustic radiation force (ARF) scaling with the volume of the object. We experimentally demonstrate acoustophoresis of several Legionella species in water and measure their acoustic contrast factor that determines the magnitude and directionality of the ARF. Furthermore, we computationally and experimentally investigate the influence of viscoacoustic and hydrodynamic interactions in multibody acoustophoresis, particularly the effects of bacteria concentration and acoustic interactions including microstreaming on the acoustic focusability. The results apply to several earlier studies.

MOMENTUM CONSERVATION AND THE 2ND LAW IN BIOLOGICAL COMMUNICATION
Matthias Schneider
Technische Universität Dortmund, GERMANY

An approach is presented in which physical properties of the interface - not individual molecules - are identified as the potential origin of biological function. We outline the importance of the interplay of momentum conservation (and hence acoustics) and thermodynamics in 2D-systems as an origin for communication between cells. The model is applied to nerve pulse communication as well as the interaction between enzymes and acoustic pulses with cellular membranes.

LEVERAGING TIME AND FREQUENCY MULTIPLEXING FOR DYNAMIC ACOUSTIC TWEEZERS
Zhenhua Tian
Virginia Tech, USA

Time-division and frequency-division multiplexing techniques are usually used for ultrasonic imaging. This talk focuses on the fusion of these multiplexing techniques and acoustic tweezers for dynamically reshaping acoustic wavefields and further achieving multifunctional and programmable cell/particle manipulation.