A multi-stimulus-responsive bionic fish microrobot for remote intelligent control applications

Light-Driven Microrobots for Targeted Drug Delivery

As a new micromanipulation tool with the advantages of small size, flexible movement and easy manipulation, light-driven microrobots have a wide range of prospects in biomedical fields such as drug targeting and cell manipulation. Recently, microrobots have been controlled in various ways, and light field has become a research hotspot by its advantages of noncontact manipulation, precise localization, fast response, and biocompatibility. It utilizes the force or deformation generated by the light field to precisely control the microrobot, and combines with the drug release technology to realize the targeted drug application. Therefore, this paper provides an overview of light-driven microrobots with drug targeting to provide new ideas for the manipulation of microrobots. Here, this paper briefly categorizes the driving mechanisms and materials of light-driven microrobots, which mainly include photothermal, photochemical, and biological. Then, typical designs of light-driven microrobots with different driving mechanisms and control strategies for multiple physical fields are summarized. Finally, the applications of microrobots in the fields of drug targeting and bioimaging are presented as well as the future prospects of light-driven microrobots in the biomedical field are demonstrated.

Multi-Stimuli-Responsive Tadpole-like Polymer/Lipid Janus Microrobots for Advanced Smart Material Applications

Microrobots are of significant interest due to their smart transport capabilities, especially for precisely targeted delivery in dynamic environments (blood, cell membranes, tumor interstitial matrixes, blood-brain barrier, mucosa, and other body fluids). To perform a more complex micromanipulation in biological applications, it is highly desirable for microrobots to be stimulated with multiple stimuli rather than a single stimulus. Herein, the biodegradable and biocompatible smart micromotors with a Janus architecture consisting of PrecirolATO 5 and polycaprolactone compartments inspired by the anisotropic geometry of tadpoles and sperms are newly designed. These bioinspired micromotors combine the advantageous properties of polypyrrole nanoparticles (NPs), a high near-infrared light-absorbing agent with high photothermal conversion efficiency, and magnetic NPs, which respond to the magnetic field and exhibit multistimulus-responsive behavior. By combining both fields, we achieved an "on/off" propulsion mechanism that can enable us to overcome complex tasks and limitations in liquid environments and overcome the limitations encountered by single actuation applications. Moreover, the magnetic particles offer other functions such as removing organic pollutants via the Fenton reaction. Janus-structured motors provide a broad perspective not only for biosensing, optical detection, and on-chip separation applications but also for environmental water treatment due to the catalytic activities of multistimulus-responsive micromotors.

Stenus-inspired, swift, and agile untethered insect-scale soft propulsors

Mimicking living creatures, soft robots exhibit incomparable adaptability and various attractive new features. However, untethered insect-scale soft robots are often plagued with inferior controllability and low kinetic performance. Systematically inspired by the swift swingable abdomen, conducting canals for secretion transport, and body setae of Stenus comma, together with magnetic-induced fast-transformed postures, herein, we present a swift, agile untethered millimetre-scale soft propulsor propelling on water. The demonstrated propulsor, with a body length (BL) of 3.6 mm, achieved a recorded specific speed of ~201 BL/s and acceleration of ~8,372 BL/s2. The comprehensive kinetic performance of this propulsor surpasses those of previous ones at similar scales by several orders. Notably, we discovered momentum-transfer-induced over-biological on-demand braking (deceleration ~-5,010 BL/s2) and elucidated the underlying hydrodynamics. This work offers new insights into systematically bio-inspired artificial insect-scale soft robots, enabling them to push boundaries in performance, and potentially revolutionizing robot design, optimization, and control paradigms.

Four-Dimensional-Printed Microrobots and Their Applications: A Review

Owing to their small size, microrobots have many potential applications. In addition, four-dimensional (4D) printing facilitates reversible shape transformation over time or upon the application of stimuli. By combining the concept of microrobots and 4D printing, it may be possible to realize more sophisticated next-generation microrobot designs that can be actuated by applying various stimuli, and also demonstrates profound implications for various applications, including drug delivery, cells delivery, soft robotics, object release and others. Herein, recent advances in 4D-printed microrobots are reviewed, including strategies for facilitating shape transformations, diverse types of external stimuli, and medical and nonmedical applications of microrobots. Finally, to conclude the paper, the challenges and the prospects of 4D-printed microrobots are highlighted.