Propulsion of Bubble-Based Acoustic Microswimmers

Bertin, Nicolas; Spelman, Tamsin; Stéphan, Olivier; Gredy, Laetitia; Bouriau, Michel; Lauga, Eric; Marmottant, Philippe

doi:10.1103/physrevapplied.4.064012

Cited by 82 publications

(119 citation statements)

References 31 publications

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“…For other applications, such as the removal of biofilms, with typical elastic modulus of 10 2 Pa and shear strength of approximately 10 Pa (Flemming, Wingender & Szewzyk 2011), it is desirable to achieve a more steady and controlled flow, even if this implies a substantially lower shear rate (Verhaagen 2012;. Such acoustic streaming flow induced by an oscillating bubble has been also used to propel microparticles (Bertin et al 2015) or even milimetric objects (Dijkink et al 2006).…”

Section: R Bolaños-jiménez and Othersmentioning

confidence: 99%

Streaming flow by oscillating bubbles: quantitative diagnostics via particle tracking velocimetry

et al. 2017

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Oscillating microbubbles can be used as microscopic agents. Using external acoustic fields they are able to set the surrounding fluid into motion, erode surfaces and even to carry particles attached to their interfaces. Although the acoustic streaming flow that the bubble generates in its vicinity has been often observed, it has never been measured and quantitatively compared with the available theoretical models. The scarcity of quantitative data is partially due to the strong three-dimensional character of bubble-induced streaming flows, which demands advanced velocimetry techniques. In this work, we present quantitative measurements of the flow generated by single and pairs of acoustically excited sessile microbubbles using a three-dimensional particle tracking technique. Using this novel experimental approach we are able to obtain the bubble's resonant oscillating frequency, study the boundaries of the linear oscillation regime, give predictions on the flow strength and the shear in the surrounding surface and study the flow and the stability of a two-bubble system. Our results show that velocimetry techniques are a suitable tool to make diagnostics on the dynamics of acoustically excited microbubbles.

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Section: R Bolaños-jiménez and Othersmentioning

confidence: 99%

Streaming flow by oscillating bubbles: quantitative diagnostics via particle tracking velocimetry

et al. 2017

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“…As the bubble diameter scales down to the 10-to 30-μm range, the cylindrical cavity geometry would require advanced hydrophobic treatment to hold a microbubble stable due to the increased surface tension forces (19). Therefore, advanced threedimensional (3D) microfabrication techniques could be used to create spherical voids inside the swimmer's body to increase the stability of a trapped air bubble (23). Previously, Louf et al (13) demonstrated a hovering microswimmer by trapping a microbubble underneath its body, facing toward the substrate.…”

mentioning

confidence: 99%

“…Moreover, their cylindrical cavity design required hydrophobic surface modification to stabilize the bubble during acoustic actuation. In general, the locomotion behavior of bubble-based microrobots in a low-Reynolds flow regime is complex, especially when the microbubble is below the 30-μm range and oscillates near solid walls, due to the nonlinear acoustic forces (23). The interaction of such acoustically powered microrobots near walls has not been fully investigated yet and therefore their directionality control remains a challenge.…”

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confidence: 99%

Acoustically powered surface-slipping mobile microrobots

Aghakhani

Yaşa

Wrede

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

219

215

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Untethered synthetic microrobots have significant potential to revolutionize minimally invasive medical interventions in the future. However, their relatively slow speed and low controllability near surfaces typically are some of the barriers standing in the way of their medical applications. Here, we introduce acoustically powered microrobots with a fast, unidirectional surface-slipping locomotion on both flat and curved surfaces. The proposed threedimensionally printed, bullet-shaped microrobot contains a spherical air bubble trapped inside its internal body cavity, where the bubble is resonated using acoustic waves. The net fluidic flow due to the bubble oscillation orients the microrobot's axisymmetric axis perpendicular to the wall and then propels it laterally at very high speeds (up to 90 body lengths per second with a body length of 25 μm) while inducing an attractive force toward the wall. To achieve unidirectional locomotion, a small fin is added to the microrobot's cylindrical body surface, which biases the propulsion direction. For motion direction control, the microrobots are coated anisotropically with a soft magnetic nanofilm layer, allowing steering under a uniform magnetic field. Finally, surface locomotion capability of the microrobots is demonstrated inside a threedimensional circular cross-sectional microchannel under acoustic actuation. Overall, the combination of acoustic powering and magnetic steering can be effectively utilized to actuate and navigate these microrobots in confined and hard-to-reach body location areas in a minimally invasive fashion. microrobots | acoustic actuation | magnetic control | microswimmers | bubble oscillation U ntethered synthetic microrobots have been recently investigated for their potential applications in targeted drug delivery, detoxification, and noninvasive surgeries (1-4). The existing microswimmers are powered by different external energy sources, such as light (5-7), electrical (8,9), magnetic (10, 11), and acoustic (12, 13) fields, or fueled by chemicals in the environment (14, 15). Among these actuation schemes, magnetic and acoustic field-based powering methods are the most prevalent in the biomedical context thanks to their deep-tissue penetration and high-energy-density capabilities. While the acoustic waves can deliver strong propulsion forces (16), the magnetic field can provide controlled steering of the microswimmers (17, 18). For example, acoustically excited bubbles can generate high streaming forces (16,19), and when employed in the robot's body they can act as an engine for the propulsion (12,20).Up to now, a few studies have used two-dimensional (2D) microfabrication (20, 21) and ultraviolet light-based polymerization techniques (12,22) to fabricate around 100-to 300-μm microrobots with cylindrical or conical cavities for bubble entrapment. As the bubble diameter scales down to the 10-to 30-μm range, the cylindrical cavity geometry would require advanced hydrophobic treatment to hold a microbubble stable due to the increased surface tens...

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“…While applied here to autophoretic propulsion, this method of control via selective shape transformation is in fact broadly applicable to other means of propulsion, which may be preferable for biomedical applications. For instance, if the catalytic end-caps were to be replaced by encapsulated bubbles driven by ultrasound [11], this swimmer would drive very similar flows to the phoretic swimmer in all three configurations, with the additional benefit of biocompatibility [39].…”

Section: Discussionmentioning

confidence: 99%

Microtransformers: Controlled microscale navigation with flexible robots

Montenegro‐Johnson

2018

Phys. Rev. Fluids

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Artificial microswimmers are a new technology with promising microfluidics and biomedical applications, such as directed cargo transport, microscale assembly, and targeted drug delivery. A fundamental barrier to realising this potential is the ability to independently control the trajectories of multiple individuals within a large group. A promising navigation mechanism for "fuel-based" microswimmers, for example autophoretic Janus particles, entails modulating the local environment to guide the swimmer, for instance by etching grooves in microchannels. However, such techniques are currently limited to bulk guidance. This paper will argue that by manufacturing microswimmers from phoretic filaments of flexible shape-memory polymer, elastic transformations can modulate swimming behaviour, allowing precision navigation of selected individuals within a group through complex environments. arXiv:1801.09742v2 [physics.flu-dyn]

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Propulsion of Bubble-Based Acoustic Microswimmers

Cited by 82 publications

References 31 publications

Streaming flow by oscillating bubbles: quantitative diagnostics via particle tracking velocimetry

Streaming flow by oscillating bubbles: quantitative diagnostics via particle tracking velocimetry

Acoustically powered surface-slipping mobile microrobots

Microtransformers: Controlled microscale navigation with flexible robots

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