Embedded Microbubbles for Acoustic Manipulation of Single Cells and Microfluidic Applications

Abstract

Acoustically excited microstructures have demonstrated significant potential for small-scale biomedical applications by overcoming major microfluidic limitations. Recently, the application of oscillating microbubbles has demonstrated their superiority over acoustically excited solid structures due to their enhanced acoustic streaming at low input power. However, their limited temporal stability hinders their direct applicability for industrial or clinical purposes. Here, we introduce the embedded microbubble, a novel acoustofluidic design based on the combination of solid structures (poly(dimethylsiloxane)) and microbubbles (air-filled cavity) to combine the benefits of both approaches while minimizing their drawbacks. We investigate the influence of various design parameters and geometrical features through numerical simulations and experimentally evaluate their manipulation capabilities. Finally, we demonstrate the capabilities of our design for microfluidic applications by investigating its mixing performance as well as through the controlled rotational manipulation of individual HeLa cells.

Acoustofluidic medium exchange for preparation of electrocompetent bacteria using channel wall trapping

“…Therefore, even when the particles reach the point of minimal Gor'kov potential and thus are no longer subjected to the acoustic radiation force, they will still be trapped in the acoustic streaming vortices nearby the thin wall. Our recent publication 73 and similar ones from other groups 71,72 demonstrate that a single streaming vortex close to the wall can be utilised to attract particles but is not sufficient to retain particles against a fluid flow.…”

“…Recently, we published a similar device design produced in polydimethylsiloxane, which is not capable of bacteria trapping but can be used for controlled single cell rotation and efficient fluid mixing. 73 …”

“…In contrast to related work showing particle attraction to channel walls, 43,71–74 we are able to retain cells as small as bacteria against a flow due to the constructive combination of the action of acoustic radiation force and acoustic streaming, lowering the critical particle radius. Furthermore, we demonstrated in a recent publication 73 that our novel device design can also be used in PDMS microchannels and, since the position of the thin vibrating wall can be chosen arbitrarily, our design is much more flexible than state-of-the-art methods presented in the literature, opening the door for novel applications. To better understand the underlying working mechanism and to enable the direct optimisation of our design, we analysed our approach's underlying mechanisms using finite element simulations.…”

Multimodal Bubble Microrobot Near an Air–Water Interface

“…The swimming microrobots using biomimetic swimming strategies and microscale fluid dynamics have recently made great improve the driving efficiency of bubble-driven microrobots and provides powerful and flexible ways of manipulation. [14] However, using microbubble to manipulate micro-cargos, as a "soft" method to replace the conventional mechanical means, is a tricky problem in microrobotics. Recent progress has shown the capability of bubble microrobots to perform functions like gripping or propelling.…”

Growth and Labelling of Cell Wall Components of the Brown Alga Ectocarpus in Microfluidic Chips

“…With advances in microtechnology driving the development of novel microelectromechanical systems (MEMS) and, consequently, the broader availability of corresponding fabrication facilities, the use of lab-on-chip devices has gained increasing interest in many research fields ranging from chemistry and biomedical engineering to biology (Azizipour et al, 2020;Bayareh et al, 2020;Pei et al, 2020;Zhu et al, 2020;Berlanda et al, 2021;Läubli et al, 2021a). As a subset of these technologies, microfluidic devices, i.e., structures containing fluid filled channels with dimensions in the µm to mm range, have been successfully established as a versatile tool that enables new avenues of research through the manipulation and handling of small organisms (Läubli et al, 2021b). In recent years, several pieces of work have relied on microfluidic technologies to study a wide range of organisms through the evolutionary tree including mammalians and plants (Peyrin et al, 2011;Siddique and Thakor, 2013;Tong et al, 2015;Shamsudhin et al, 2016;Burri et al, 2018).…”