Ultrafast Bubble-Propelled and Magnetic-Field-Navigated Porous Catalytic Janus Micromotor

Controlling the Collective Behaviors of Ultrasound-Driven Nanomotors via Frequency Regulation

Controlling the collective behavior of micro/nanomotors with ultrasound may enable new functionality in robotics, medicine, and other engineering disciplines. Currently, various collective behaviors of nanomotors, such as assembly, reconfiguration, and disassembly, have been explored by using acoustic fields with a fixed frequency, while regulating their collective behaviors by varying the ultrasound frequency still remains challenging. In this work, we designed an ultrasound manipulation methodology that allows nanomotors to exhibit different collective behaviors by regulating the applied ultrasound frequency. The experimental results and FEM simulations demonstrate that the secondary ultrasonic waves produced from the edge of the sample cell lead to the formation of complex acoustic pressure fields and microfluidic patterns, which causes these collective behaviors. This work has important implications for the design of artificial actuated nanomotors and optimize their performances.

Gold-hyaluranic acid micromotors and cold atmospheric plasma for enhanced drug delivery and therapeutic applications

Micro/nanomotors have emerged as promising platforms for various applications, including drug delivery and controlled release. These tiny machines, built from nanoscale materials such as carbon nanotubes, graphene, metal nanoparticles, or nanowires, can convert different forms of energy into mechanical motion. In the field of medicine, nanomotors offer potential for targeted drug delivery and diagnostic applications, revolutionizing areas such as cancer treatment and lab-on-a-chip devices. One prominent material used in drug delivery is hyaluronic acid (HA), known for its biocompatibility and non-immunogenicity. HA-based drug delivery systems have shown promise in improving the efficacy and reducing the toxicity of chemotherapeutic agents like doxorubicin (DOX). Additionally, micro/nanomotors controlled by external stimuli enable precise drug delivery to specific areas of the body. Cold atmospheric plasma (CAP) has also emerged as a promising technology for drug delivery, utilizing low-temperature plasma to enhance drug release and bioavailability. CAP offers advantages such as localized delivery and compatibility with various drug types. However, further research is needed to optimize CAP drug delivery systems and understand their mechanisms. In this study, gold-hyaluronic acid (Au-HA) micromotors were synthesized for the first time, utilizing acoustic force for self-motion. The release profile of DOX, a widely used anticancer drug, was investigated in pH-dependent conditions, and the effect of CAP on drug release from the micromotors was examined. Following exposure to the CAP jet for 1 min, the micromotors released approximately 29 μg mL-1 of DOX into the PBS (pH 5), which is significantly higher than the 17 μg mL-1 released without CAP. The research aims to minimize side effects, increase drug loading and release efficiency, and highlight the potential of HA-based micromotors in cancer therapy. This study contributes to the advancement of micro-motor technology and provides insights into the utilization of pH and cold plasma technology for enhancing drug delivery systems.

Highly Efficient Magnetic Propulsion of NiFe Nanorod-Based Miniature Swimmers in Three Dimensions

Magnetically actuated miniature robots have attracted the attention of the scientific community over the past two decades, but the confined workspace of their manipulation system (typically a tri-axial coil or eight electromagnetic coils) and the low efficiency of propulsion have limited their utility. Here, we describe a highly efficient NiFe nanorod-based magnetic miniature swimmer that can be manipulated in 3D spaces using two pairs of coils placed in the x-y horizontal plane. In the new swimmer, the shape symmetry is broken along its body, and the asymmetry in magnetizations is introduced perpendicular to the long axis of its body simultaneously. Such a combined asymmetry design offers favorable controllability in planar magnetic fields, which relaxes the multi-axial coil requirement of the commonly used manipulation system and thus reduces the restriction on the shape and size of the workspaces. The new swimmers display efficient 3D propulsion, with a speed of over 5000 μm s^-1 (∼3 body length s^-1) and powerful locomotion in biological media such as raw human blood. The fuel utilization efficiency of the swimmer, defined as the ratio of the distance to the net input work in one period, was estimated to be approximately from 10^-2 to 10^-3 m/J, which is significantly higher than that of magnetic motors with a slender body. Moreover, to provide practical support for further potential use, we demonstrated that the swimmer is able to perform incision operations as a minimally invasive microsurgical tool. Such a swimmer actuation strategy provides a simple and efficient way for 3D manipulation of magnetic miniature robots, offering great potential for future biomedical and other applications.

Magnetically Powered Shape-Transformable Liquid Metal Micromotors

Shape-transformable liquid metal (LM) micromachines have attracted the attention of the scientific community over the past 5 years, but the inconvenience of transfer routes and the use of corrosive fuels have limited their potential applications. In this work, a shape-transformable LM micromotor that is fabricated by a simple, versatile ice-assisted transfer printing method is demonstrated, in which an ice layer is employed as a "sacrificial" substrate that can enable the direct transfer of LM micromotors to arbitrary target substrates conveniently. The resulting LM microswimmers display efficient propulsion of over 60 µm s^-1 (≈3 bodylength s^-1 ) under elliptically polarized magnetic fields, comparable to that of the common magnetic micro/nanomotors with rigid bodies. Moreover, these LM micromotors can undergo dramatic morphological transformation in an aqueous environment under the irradiation of an alternating magnetic field. The ability to transform the shape and efficiently propel LM microswimmers holds great promise for chemical sensing, controlled cargo transport, materials science, and even artificial intelligence in ways that are not possible with rigid-bodies microrobots.