Recent Process in Microrobots: From Propulsion to Swarming for Biomedical Applications

Abstract

Recently, robots have assisted and contributed to the biomedical field. Scaling down the size of robots to micro/nanoscale can increase the accuracy of targeted medications and decrease the danger of invasive operations in human surgery. Inspired by the motion pattern and collective behaviors of the tiny biological motors in nature, various kinds of sophisticated and programmable microrobots are fabricated with the ability for cargo delivery, bio-imaging, precise operation, etc. In this review, four types of propulsion—magnetically, acoustically, chemically/optically and hybrid driven—and their corresponding features have been outlined and categorized. In particular, the locomotion of these micro/nanorobots, as well as the requirement of biocompatibility, transportation efficiency, and controllable motion for applications in the complex human body environment should be considered. We discuss applications of different propulsion mechanisms in the biomedical field, list their individual benefits, and suggest their potential growth paths.

Actuation of Mobile Microbots: A Review

“…Self‐electrophoresis, on the other hand, involves the generation of a proton flow, distinguishing it from self‐diffusiophoresis. [ 169 ] Gas propelled micro‐swimmers, usually in the form of particles ( Figure a,b) or micro‐rockets (Figure 10c), are particles decorated or coated with catalytic materials. The most typical particle micro‐swimmers are Janus particles (Figure 10a) which are usually colloids with one side treated differently, commonly by applying catalytic coatings.…”

Collective motion of Nafion-based micromotors in water

“…This can lead to the emergence of complex and fascinating phenomena, such as pattern formation, swarming behavior, and motion synchronization, similar to natural active matter systems, such as swarms of bacteria or schools of fish. 13–21…”

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

“…Synthetic micro-/nanomotors with autonomous functionalities are of great interest due to their unique motion behavior, especially for active targeted delivery in biomimetic and intelligent transportation. − However, the effective actuation and manipulation of micro-/nanomotors is prevented by some limiting factors, such as the low Reynolds number regime where viscosity and Brownian motion occur. − To overcome the limitations of swimming, considering that all living systems can adapt to complex and variable living environments with their unique characteristics, many studies have focused on bioinspired micro-/nanosystems, such as the swimming of fish, opening and closing of flowers, and crawling of snakes while designing multifunctional platforms that actively respond to dynamic environmental factors. − In addition, the nature-inspired systems have been combined with fundamental concepts, including the Marangoni effect (such as pH, temperature, magnetic field, electric field, ultrasonic field, and light field), self-diffusiophoresis, self-electrophoresis, and bubble propulsion, to stimulate and actuate micrometer-sized systems in a liquid environment. ,, Single-stimulated micromotors are not suitable for complex environments, where complex movements cannot be achieved. In fact, multiple-stimulus-stimulated micromotors have begun to attract more and more attention than single-stimulated ones for active targeting due to their capability of overcoming various biological barriers (blood, cell membrane, tumor interstitial matrix, blood–brain barrier, mucosa, and other body fluids). , …”