Wireless Acoustic-Surface Actuators for Miniaturized Endoscopes

Qiu, Tian; Adams, Fabian; Palagi, Stefano; Melde, Kai; Mark, Andrew; Wetterauer, Ulrich; Miernik, Arkadiusz; Fischer, Peer

doi:10.1021/acsami.7b12755

Cited by 23 publications

(18 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We attribute the shift between the experimental and numerical resonant frequency of the microbubble to the surface tension-induced stiffness component, which is missing in the simulation environment (SI Appendix, section S2). Unlike other reported bubble-based swimmers in the literature (12,22,30) with bubble radius bigger than 30 μm, at scales related to our design the effect of surface tension is significant. Indeed, using a scaling analysis, we found that the ratio of surface tension to volumetric pressure change is around 3 (SI Appendix, section S2).…”

Section: Characterization Of the Microbubble Resonance Frequency Andmentioning

confidence: 61%

Acoustically powered surface-slipping mobile microrobots

Aghakhani

Yaşa

Wrede

et al. 2020

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

222

215

View full text Add to dashboard Cite

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...

show abstract

Section: Characterization Of the Microbubble Resonance Frequency Andmentioning

confidence: 61%

Acoustically powered surface-slipping mobile microrobots

Aghakhani

Yaşa

Wrede

et al. 2020

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

222

215

View full text Add to dashboard Cite

show abstract

“…Various SAW devices have the potential to be commercialized into flexible diagnostic platforms that may be transformed into wearable devices. A collaboration between different SAW and streaming-driven tweezers can push the boundaries of their traditional usage in microfluidics, to design of acoustically driven surgical devices [140]. Lastly, we discuss self-propelling micro-agents with on-board vibrational units designed to resonate at specific acoustic frequencies.…”

Section: Resultsmentioning

confidence: 99%

Contactless acoustic micro/nano manipulation: a paradigm for next generation applications in life sciences

2020

View full text Add to dashboard Cite

Acoustic actuation techniques offer a promising tool for contactless manipulation of both synthetic and biological micro/nano agents that encompass different length scales. The traditional usage of sound waves has steadily progressed from mid-air manipulation of salt grains to sophisticated techniques that employ nanoparticle flow in microfluidic networks. State-of-the-art in microfabrication and instrumentation have further expanded the outreach of these actuation techniques to autonomous propulsion of micro-agents. In this review article, we provide a universal perspective of the known acoustic micromanipulation technologies in terms of their applications and governing physics. Hereby, we survey these technologies and classify them with regards to passive and active manipulation of agents. These manipulation methods account for both intelligent devices adept at dexterous non-contact handling of micro-agents, and acoustically induced mechanisms for self-propulsion of micro-robots. Moreover, owing to the clinical compliance of ultrasound, we provide future considerations of acoustic manipulation techniques to be fruitfully employed in biological applications that range from label-free drug testing to minimally invasive clinical interventions.

show abstract

“…Therefore, any contaminants or dirt having the size similar or smaller than microrobots could increase the risk of stiction which can perturb their sustainable and robust motions and functionalities. Various microrobots have been studied and demonstrated in their propulsions remotely powered by optical [3][4][5], acoustic [6][7][8], chemical [9,10] or magnetic energy [11][12][13][14]. The microfluidic channel applications could amplify such risk of stiction due to increased channel walls influences.…”

mentioning

confidence: 99%