3D steerable, acoustically powered microswimmers for single-particle manipulation

Abstract

The ability to precisely maneuver micro/nano objects in fluids in a contactless, biocompatible manner can enable innovative technologies and may have far-reaching impact in fields such as biology, chemical engineering, and nanotechnology. Here, we report a design for acoustically powered bubble-based microswimmers that are capable of autonomous motion in three dimensions and selectively transporting individual synthetic colloids and mammalian cells in a crowded group without labeling, surface modification, or effect on nearby objects. In contrast to previously reported microswimmers, their motion does not require operation at acoustic pressure nodes, enabling propulsion at low power and far from an ultrasonic transducer. In a megahertz acoustic field, the microswimmers are subject to two predominant forces: the secondary Bjerknes force and a locally generated acoustic streaming propulsive force. The combination of these two forces enables the microswimmers to independently swim on three dimensional boundaries or in free space under magnetical steering.

Advances in Micromanipulation Actuated by Vibration-Induced Acoustic Waves and Streaming Flow

“…Compared with microbubbles, microrobots are more stable and their mechanical properties are more prominent, but their manufacturing costs are higher and their use involves some difficulties. Some schemes combine microbubbles and microrobots, such as Ren et al [83] (Figure 7d). A microbubble was enclosed in a semi-capsule-shaped robot, and the secondary Bjerknes force formed between the bubble and the actuator was used to drive the microrobot motion.…”

“…A microbubble was enclosed in a semi-capsule-shaped robot, and the secondary Bjerknes force formed between the bubble and the actuator was used to drive the microrobot motion. [31], Ahmed et al [77,78], Xie et al [81,82], and Ren et al [83]. The reason why microbubbles and microrobots are classified into one category is that they both perform secondary micromanipulation, which means that their motion requires manipulation, and their motion characteristics drive the micromanipulation for other particles.…”

A Customizable DNA and Microsphere-Based, Magnetically Actuated Microswimmer

“…R OBOTS capable of swimming at the microscale, microswimmers, have great potential as tools for a diverse set of applications such as drug delivery [1], micromixing [2], and micromanufacturing [3]. Due to their small size, microswimmers are difficult to manufacture and are generally controlled by an outside stimulus, e.g., a magnet that responds to an external field.…”

Addressable Acoustic Actuation of 3D Printed Soft Robotic Microsystems

“…Bubbles and sharp-edged solid structures excited by acoustic waves generate steady streaming in liquids, [28][29][30][31] providing a minimally invasive and scalable solution for powering untethered micromachines in vivo. [32][33][34][35][36] While bubbles are quite efficient in transducing acoustic energy, [37] microrobotic systems actuated by entrapped bubbles work reliable only for hours. [34,35] The size and mechanical response of bubbles do not stay the same under physiological conditions, thereby gradually shifting the resonance frequency of the actuators and deteriorating the performance of the machine.…”

“…[32][33][34][35][36] While bubbles are quite efficient in transducing acoustic energy, [37] microrobotic systems actuated by entrapped bubbles work reliable only for hours. [34,35] The size and mechanical response of bubbles do not stay the same under physiological conditions, thereby gradually shifting the resonance frequency of the actuators and deteriorating the performance of the machine. Furthermore, stable entrapment and precise actuation of multiple bubbles inside a compartmentalized microrobot is quite challenging due to surface effects.…”